SOME  NOTES

Consider the generalisations people have about lighting and how the scene is going to look.

180-DEGREE  RULE

Is a basic guideline regarding the on-screen spatial relationship between a character and another character or object within a scene. An imaginary line called the axis connects the characters, and by keeping the camera on one side of this axis for every shot in the scene, the first character is always frame right of the second character, who is then always frame left of the first. The camera passing over the axis is called jumping the line or crossing the line; breaking the 180-degree rule by shooting on all sides is known as shooting in the round.

The continuity of the character’s movement needs to be consistent as they move across the frame to avoid confusing the audience with changes in direction and orientation. There is a 180º arc or imaginary line with the camera to one side of that line.

ELECTROMAGNETIC  SPECTRUM

Light is manifested as a wave or particle, the space between the waves are wavelengths or distance between the crests. The height or trough of the crest is the amplitude and the speed of the crests move based on a fixed given point is the frequency.

INVERSE  SQUARE  LAW

Light fading over distance, affecting the apparent brightness or perceived brightness. Intrinsic brightness is the lights’s own energy emission per second, which is luminosity.

WEIN’S  LAW

The wavelength of the peak radiance decreases linearly as the temperature increases, the hotter the object, the bluer the radiation it emits. Cold objects are not visible at night and burning objects give off heat and visible light. Studying heat and its colour emission is known as black body radiation.

COLOUR  TEMPERATURE

Measured in the Kelvin scale in degrees.

EIGHTEEN-PERCENT  GREY

Is when equal amounts of what and black paint are mixed together.

THE  LAW  of  REFLECTION

The angle of the reflection equals the angle of the incidence as relative to the surface’s normal, a line perpendicular to the reflecting surface at the point of incidence.

SNELL’S  LAW

The angles of incidence and refraction is a constant on opposite sides of the normal at the point of incidence or entry.  The bending of light as it crosses a boundary causes magnification and distortion, critical angle.

Cornell Box, is a test aimed at determining the accuracy of rendering software by comparing the rendered scene with an actual photograph of the same scene, and has become a commonly used 3D test model.

Anisotropy reflections are just like regular reflections, except stretched or blurred based on the orientation of small grooves (bumps, fibers or scratches) that exist on a reflective surface. They are stretched in a direction perpendicular to the grooves, channels or undulations of the reflecting surface. So now how do we replicate them in 3d?

BRDF or Bidirectional Reflectance Distribution Function, defines how light is reflected at an opaque surface. It is employed both in the optics of real-world light, in computer graphics algorithms, and in computer vision algorithms.  The reflective quality of diffuse surfaces with the strength based on the viewing angle, the incident angle between the viewer and the surface normal and the inherent properties of the surface.

Ambient Occlusion, allows you to simulate the soft shadows that occur in the cracks and crevices of your 3D objects when indirect lighting is cast out onto your scene.  Additional soft shadows that are created inside surface convolutions and where surfaces are in close proximity.  It can help to define the separation between objects in your scene and add another level of realism to the render.   The darkened areas are usually where there are cracks, crevices and where one surface sits close to another, calculating whether a surface point is blocked by nearby surfaces, potentially reducing the amount of light the surface point receives.

A ray of light being refracted in a plastic block

IOR or index of refraction, describes how light propagates through that medium, how much light is bent, or refracted, when entering a material.  The number indicates the change in the speed of light when a light ray crosses the country between two materials, producing subtle variation in the diffuse quality of opaque surfaces, the way the surface scatters light.  Isotropic, Anisotropic.

http://stackoverflow.com/questions/27691721/having-trouble-implementing-photon-mapping

Photon Mapping, the realism of ray tracing can be improved by simulating individual photons that are emitted from a light source and bounce around the scene. Leading to realistic color bleeding and soft shadows. Effects like caustics that are very difficult to compute using traditional Monte Carlo ray tracing are easily obtained with the photon map.  It involves the constructing the photon map by emitting photons from the light sources in the model and storing these in the photon map as they hit surfaces.

• A Practical Guide to Global Illumination using Photon Maps Siggraph 2000 Course 
• The Secret Life of Photons
• Raytracing / Photon mapping

Some renders fully account the light transfer from the light source to the material and back out the material and then the light path is traced again from the eye back into the environment; the intersection of these two rays and subsequent ray generation is computed.   These are the so-called bi-directional retracers, which can generate caustics or focused specularity through refraction or reflection.

arnold, motion vector aov

Motion Vextor encodes the option of an object into an image’s colour channels, they compress and store changes to an image from one frame to the next. The process is a bi-dimensional pointer that communicates to the decoder how much left or right and up or down, the prediction macroblock is located from the position of the macroblock in the reference frame or field.  The Motion Vector AOV outputs a color channel that shows object movement within the scene. This AOV can be used by post-processing software to calculate a 2D motion blur effect. The advantage is that it is usually quicker to render compared to true 3D motion blur.  Another way to create a motion vector pass is to use a custom AOV and assign an Ai Motion Vector shader to the default ‘Shader’ attribute.

Z depth channel viewed within Nuke

focal-plane setup enabled (green area is in focus)

Z Depth, AOV contains the depth information of the shading points.  Encodes the distance from the camera to a surface point.  Is the management of image depth coordinates in 3D graphics, usually done in hardware, sometimes in software. It is one solution to the visibility problem, which is the problem of deciding which elements of a rendered scene are visible, and which are hidden. When an object is rendered, the depth of a generated pixel (z coordinate) is stored in a buffer (the z-buffer or depth buffer). This buffer is usually arranged as a two-dimensional array (x-y) with one element for each screen pixel. If another object of the scene must be rendered in the same pixel, the method compares the two depths and overrides the current pixel if the object is closer to the observer. The chosen depth is then saved to the z-buffer, replacing the old one. In the end, the z-buffer will allow the method to correctly reproduce the usual depth perception: a close object hides a farther one. This is called z-culling.

Mattes are used to cue or block a part of another render pass.  The matte option enables you to create houldout effects by rendering the alpha as zero. The matte options are available for the Ai Standard, Ai Hair and Ai Skin shaders.  In addition, an image can include an invisible fourth channel, called an alpha channel, that contains transparency information.  They define transparency and often delineate objects or selections as a matte or stencil. Alpha channels can come pre-matted (“shaped”) or as straight, with transparency anti-aliased only when composited.

Normal, the normal at shading point, encodes the surface normal direction and maybe relative to the camera particular light or the surface itself in object or world space.

Render Layers, instead of rendering the whole shot the shot is divided into layers for key elements.  Specifically referring to separating different objects into separate images, such as a layer each for foreground characters, sets, effect, shadows, distant landscape and sky and they are rendered separately for efficiency.

Render Passes or AOVs in Arnold, further divides the shot into specific shading components, lighting contributions or compositing encoders such as colour, diffuse, specularity, reflectivity, depth, ambient occlusion, reflection occlusion, surface normal and motion vector renders.  Rendering in passes refers to separating out different aspects of the scene, such as shadows, highlights, or reflections, into separate images.

Contribution Maps, custom frame buffers, to customise the render passes further for each layer. It specifies which objects and lights are included in a render pass. By default the created render pass includes all the associated objects on that layer.  Using a contribution map enables the the inclusion of only certain lights and objects to the render pass giving more flexibility when rendering for compositing.

Overrides as surfaces assigned to a render layer are illuminated only by the lights that have ben assigned to the render layer.  This including surfaces cast shadows and receive shadows only if these lights and objects are included in the layer. Overrides changes this such as preventing a surface from casting shadows on a particular layer.  Material overrides are nondestructive, not affecting the original material assigned on the master layer.  Render setting overrides using different render settings for different render layers, changing the master settings are passed up to al the other players except where an override has been applied.  Feature Overrides for Solid Angle’s Arnold renderer.  Light Overrides

Shadow, Arnold’s ‘Ai ShadowCatcher’ is a specific shader, used typically on floor planes in order to ‘catch’ shadows from lighting within the scene.

SOME NOTES FROM READING the following wonderful and very interesting books:

Schoolism class Rendering Reflective Surfaces with Scott Robertson

Gallardo, A., 2000. 3D lighting: history, concepts and techniques. Charles River Media, Rockland, Mass.

Robertson, S., 2014. How to render: the fundamentals of light, shadow and reflectivity. Design Studio Press, Culver City, CA.

Thomas Bertling

Scott Robertson Workshops

Gurney, J., 2010. Color and light: a guide for the realist painter. Andrews McMeel ; Simon & Schuster [distributor], Kansas City, Mo. : London.

James Gurney webblog

James Gurney youtube

Derek Jenson Blog and IES Light Profiles

Live Blog: Margaret Livingstone, “What Art can tell us about the Brain”

https://www.youtube.com/watch?v=338GgSbZUYU

Livingstone, M., 2008. Vision and art: the biology of seeing. Abrams, New York.

Lessons Learned from Scott Robertson’s How to Render Book – HUGE MATERIALS TUTORIAL

Goethe’s theory, Ewald Herin, Thomas Young, Sir Isaac Newton, Carl Jung, Albert Munsell, Ernst Gombrich, James Gurney, Colour Wheel, Colour Space, Hue Plane, CIE Colour Plane, Primary Colours, Complementary, Chroma, Value, Hue, Peak Chroma Value, Local Colour, Gradation, Tints, Perception, Luminance, Black, White, Chiaroscuro, Counter Shading, Perspective, Shading, Occlusion, Haze, Depth Perception, Relative Motion, Centre Surround, Stereopsis, Relative Motion, Atmosphere, Additive, Subtractive, Subtractive, Achromatic, Analogous, Monochromatic, Contrast, Chromatic Adaptation, Successive Contrast, Simultaneous Contrast, Warm, Cool, Colour Opposites, Colour Constancy, Kelvin, Colour Temperature, Additive Colour Mixing, Triads, Colour Accents, Colour Strings, Gamut Mapping, Colour Scripting, Subjective Primaries, Subjective Neutral, Saturated cost, Edges, Depth, Chromotherapy, Rayleigh scattering, Solar Glare, Horizon Glow, Antisolar Point, Well of the Sky, Atmospheric Perspective, Golden Hour Lighting, Sunsets, Fog, Mist, Smoke, Dust, Rainbows, Sunbeams, Shadow Beams, Dappled Light, Cloud Shadows, Snow, Ice, Water.

As light interacts with matter manifests itself in many ways reflection or bounding back, refraction or bending, transmission or through, diffraction or bending around edges, interference results in changed waves, scattering or spreading, diffusion or even scattering, absorption or retention , polarisation or selective transmission and dispersion with different wave lenghts for different materials.  There needs to be a separation between the objects in the foreground and the background.

LUMINANCE, value or perceived lightness, how bright a light is. The luminance of any particular number photons varies depending on the wavelength of that light. It is the luminance makes it possible for us to recognise objects, perceive three dimensional shapes and spacial organisation.  But appears dim and yellow seems bright. It is a per ceptual measurement, not a physical constant and changes it changes with high or low light levels.

DAY LUMINANCE VS. NIGHT LUMINANCE, the luminosity response curve and apparent brightness of different wavelengths.

PURKINJE  EFFECT or dark adaptation is the tendency for the peak luminance sensitivity of the human eye to shift toward the blue end of the color spectrum at low illumination levels, the reds darker and the blues lighter.  The difference in the rod and cone responses as a function of wavelength.  Most sensitive to greenish wavelengths of light resulting in blue-green hues appearing lighter in tone in dim conditions.

CORNSWEET  ILLUSION is an optical illusion.  The image at right, the entire region to the right of the “edge” in the middle looks slightly lighter than the area to the left of the edge, but in fact the brightness of both areas is exactly the same, as can be seen by blacking out the region containing the edge.  Our visual systems are selectively sensitive to discontinuities and not to gradual changes in luminance

The Cornsweet Illusion explained

PHOTONS: is an elementary particle, the quantum of all forms of electromagnetic radiation including light  and I thought it was something to do with 3D computer rendering software, they actually exist. Invisible units (or quanta) of light energy, called photons, travelling in a wavelike manner. What is light made of?  What can we see? Charged particles are moving. Luminescence and  Incandescence which is created by heated materials such as the sun, fire, tungsten lamps containing many wavelengths.

INTERFERENCE of waves:  what happens when two waves meet while they travel through the same medium? What effect will the meeting of the waves have upon the appearance of the medium? Will the two waves bounce off each other upon meeting (much like two billiard balls would) or will the two waves pass through each other? These questions involving the meeting of two or more waves along the same medium pertain to the topic of wave interference.

An oil slick looks clouded because of interference. If the reflections of light  striking the top and bottom layer of the oil are in phase (the peaks and droughts of the waves concise) the lightwaves will reinforce each other.  If the thickness of the oil from matches the wavelength of a particular colour then the slick will look more like that colour.  White light is reflected form two parallel surfaces very close to each other.  The iridescence of soap bubbles is due to thin-film interference.  Other examples are butterfly wings, oyster shells, opals and battle carapaces.  The colours change with viewing angle because the distance light travels changes with the angle of the light hitting the surface.

DIFFRACTION involves a change in direction of waves as they pass through an opening or around a barrier in their path.  The light is reflected from a surface that has striations spaced on the scale of the wavelength of light, some wavelengths reflect in phase and others out of phase.  Examples such as butterfly and bird wings due to the fine, regular striations and CD’s.  The colours change with viewing angle because the distance light travels changes with the angle of the light hitting the surface.

VISUAL  PERCEPTION  is the ability to interpret the surrounding environment by processing information that is contained in visible light. The resulting perception is also known as eyesight, sight, or vision.  Recognising objects, animals, people, colours, motion, depth, left or right and seeing complex objects as a whole.

EQUILUMINANT  COLOURS we cannot perceive the edges of objects where object and background have the same luminance. If parts of a painting are equiluminant, their positions become ambiguous. They may seem to shift position or to float. Luminance differences affect our perceptions.

Luminance Differences Affect Our Perceptions.  Artists use the technique of “equiluminance” to blur outlines and suggest motion. We cannot perceive the edges of objects where object and background have the same luminance. If parts of a painting are equiluminant, their positions become ambiguous. They may seem to shift position or to float.  Plus Reversed, Richard Anuszkiewicz, 1960.

CENTRAL and PERIPHERAL  VISION  Our vision is sharpest at the centre of gaze for fine detail, peripheral vision is a part of vision that occurs outside the very center of gaze being used to organise spatial information and we usually move our centre of gaze to whatever we want to look at.  What information is in the fine, medium or coarse components of an image, our central vision does not perceive coarse image components very well.  Are we more able to correctly internet facial expressions in our peripheral visions? Why does our visual system complete incomplete pictures for us, spatial imprecision?

https://www.youtube.com/watch?v=Yier5TXyuWA

SPATIAL  RESOLUTION and ECCENTRICITY – eccentricity is the degrees of visual angle from the center of the eye so what determines where we look?  The resolution of high-contrast, fine detail or higher resolution and items of biology and can be picked out by our peripheral vision.

COLOURS There is so much information about this what can be said?  Colour is low resolution and course, we do not have to colour inside the lines.

Our brains process colour information separately from luminance information, there is a difference. Hue tells us about surface chemistry, biologically information. Vary the luminance of colours without changing their saturation with variations in reflected light became known as chiaroscuro. A wide range of luminance creating a vivid depth from shading.

Colour constancy, the ability to perceive colour in its original hue even under different lighting conditions.

How the brain visually interprets the world around us, rendering based on physics and science. use a monochromatic palette to start with, looking at matching perspective, light direction and angle.  Design the light in the way that works best to communicate the form.

Objects surfaces are shaded based on the material properties of the object and need to consider the way light affects the object’s material.

http://www.falloutsoftware.com/tutorials/gl/gl8.htm

Local Illumination is the direct illumination from a light source, not including interject reflections and light bounced around the environment.

Global illumination accounts for the indirect reflected light in the scene simulating the diffuse and specular light.

Ambient light is the sum of all the indirect light reflections in the scene.

Shading is created when different parts of a surface reflect different amounts of light depending on the angle of the light hitting the object. There is an orderly and predictable serious of tones. Why is the luminance independent of colour. Vary the luminance of colours without changing their saturation with variations in reflected light became known as chiaroscuro.  Greys mixed frombhue and orange, red and green or violet and yellow.  Constant, Flat, Gouraud, Phong, Lambertian and Blinn.

Values across a surface, bump, edges. Lightness or darkness of colour, variations in light and darkness. Surfaces defined by their difference in value, not by outlines by light to dark values. There is the lightest surface, mid-value surface which still has direct and clearly differentiates the edge/surface change with the lightest then there is the shadow side which is the darkest surface. The shadow surface clearly differentiate the edge/surface change with mid-values and giving a three dimensional volume.

Diffuse, colour, weight, roughness for diffuse reflections, colour info without spec, perceived as the color of the object itself rather than a reflection of the light.  It represents direct light hitting a surface, dependent on the incident angle, light hitting a surface at a 90 degree angle contributes more than light hitting the same surface at a 5 degrees.

Ambient light is the light that enters a room and bounces multiple times around the room before lighting a particular object. Ambient light contribution depends on the light’s ambient color and the ambient’s material color.

Specular light is dependent on the direction of the light, the surface normal and the viewer location.

A specular highlight is the bright spot of light that appears on shiny objects when illuminated (for example, see image at right). Specular highlights are important in 3D computer graphics, as they provide a strong visual cue for the shape of an object and its location with respect to light sources in the scene.  Specular highlights are reflections of bright light sources.  Secular reflections are as varied as the bright light sources that create them and the surfaces on which they appear.

Reflection, Glossiness for mirror-like or degraded.  Objects appearing in reflections.

https://www.ice.rwth-aachen.de/research/tools-projects/grace/ray-traycing/

Ray tracing uses rays or photos to keep track of the light path in a scene determining the colour or chroma and brightness of luminance of each pixel. The ray determines whether the surface is reflective, refractive or luminous. Forward, backward, bidirectional ray tracing, radiosity, view dependence, view independence, thermodynamics, discretization, tone mapping.

Lights, is each light serving a single purpose, multi point source lighting, how is it colouring an object and illuminating the surface considering intensity, colour temperature, falloff, placement and position.

https://www.youtube.com/watch?v=_JVYjM7N2JE

Can create the main light first then peripheral lights that are 3/4 or 1/2 the intensity of the main light. Secondary lights can function as a kind of shadow tonality control, the shadow density.  A non-shadow casting light to fill the shadows without a fill light. More complex lighting set ups can include diamond shaped, pyramid, dome, ring, box, tubular, combination

5 Good Reasons to Use Light Texture

ARNOLD – LIGHTING/SHADERS V002

COLOURED  LIGHT  INTERACTIONS, additive colour mixing.  Blend the colour in the eye with a higher value then either light alone. The resulting hues differ with green and red mixed to make yellow. If there are two light sources of different colours shining on the same form, the last shadow from each light source will be the colour of the other source.

Three-Quarter Lighting, 45º from the front leaving a fraction of the form in shadow.

Frontal lighting shining directly at the subject.

Hard light is direct light

Soft light has many different points of light

Spot light

Non shadow casting lights

High and Low Key Lighting

Lighting ratio is the measured f-stop difference between the key leith and the fill light, difference between the lighter and darker sides considering light placement, elevation and intensity and consider the tones in the scene.

http://www.3drender.com/light/3point.html

Key Light, dominant and obvious light is the main, principal light.  The placing of the key light near the camera results in front lighting.  Side lighting is the placement at 90º to the side of the subject and rembrandt lighting places the light 45º to the camera, elevated a bit above the subject illuminating three-quarters of the subject. Broad lighting lights the subject from the same direction as the camera with a three-quarters turned face, illuminating the broad side of the object.  Short lighting has the narrow side of the turned object or face illuminated.  Top lighting has the key light positioned at the top and can be to the side, called butterfly lighting.  Under or Down lighting is what it says, the key light is below the subject illuminating from the bottom creating unusual shadows. Backlighting positions the key light either above or behind the subject creating intense highlight glow outlines with volume and depth visually separating the foreground and background.  The key light is often placed outside the actor’s look, looking between the camera and the light.

For the key light consider the height, angle, direction, position, distance, type, intensity, elevation, size, colour and the shadows it is creating.

http://design-draw-visualize.blogspot.com.au

Fill light affects both the object and the cast shadow, they are secondary lights simulating indirect illumination.  It can be set to have equal intensity to the key light and controlled through the distance or adjust the intensity or both the distance and intensity are adjusted to create the lighting.  They can be positioned opposite the main light, close to or in from of the camera considering shadow tones, overall contrast and to avoid secondary shadows.

Edge, Rim or Kicker is outlining with value, coming from behind to touch the sides of a form separating it from the background.  When the sun is low in the sky.  The kicker is filling in the shadow areas with bounced or reflected light.  The rim with the light behind and slightly offset creating an edge highlight, showing off a profile.

Supplementary lighting can be chandeliers, table lamps, portable lights, candles, flashlights, car’s headlights, campfire and can be used for motivational lighting.

Skylight, Dome light is a collection of diffuse light with the brightness varying across the sky with light scattering and transmission through the atmosphere, light dispersion.

Moon light creates dark, directional shadows with either bluish white to light blue grey light.  Could have a white or bluish-white key and a blue fill light or a blue key light and consider having the specular highlights and upper areas a yellow-white like the sun.  Look at it as reflected sunlight with low intensity.

Artificial Lights:  Incandescent lights, burn at a lower temperature than the lighting giving an orange-yellow light. Fluorescent lights, white coloured lights that burn cool. Vapour-Filled lamps. Metal Halides, HID lamps. Sodium Lamps, HID lamps. They are perceived by the human eyes differently from the way they register on film. In CG consider following the way they register on film or video as the highlights, middle tones and shadows register differently.

Candle and Fire Light are yellow-orange in colour, weak and dropping off rapidly.  At night it comes more noticeable.

Candle light burns as about 2300 – 2500K  with a colour shift to the yellows and reds in all visible illuminated objects wrapping around the object with subtle tonal graduations.  Candle light middle tones tend to be desaturated and colourless becoming grey instead of shifting their colour to grey.  Focus more on the highlights and middle tones rather than the shadows. Consider tis for most local lights.

Fire Light, consider using an array with yellowish near the base and reddish-orange for the flame above.

Centre Jour, type of backlighting where the subject blocks the light, the colours lose saturation and shadows stretch forward. Might help to have some colour int he background haze and lower a bit from white.

Below light, usually from warm orange glow of firelight, blue flicker of computer screen, reflected from reading a book, light hitting smoke or dust kicked up for some reason. This could include lighting part of a form and falling off rapidly with small, weak lights.

Half lighting usually for visual interest and/or a focal point.

Ambient light adjustments, light strength determines the darkness of cast shadows.  It is the light left when the key light is removed.

Reflected light will affect nearby shadow areas, could pick up the colours of other objects, the sky, the ground or a combination depending on where the light is reflected from.

Transmitted Light , travels through a thin, semitransparent material and becomes coloured such as leaves, balloon.  Transmitted, down facing shadow, up facing shadow and top lit.

Translucence and subsurface scattering has light spread out under the surface creating a glow affecting forms with depth and volume.  The contrast of the matte-surface is minimised and has a weaker shadow side and core shadow while the colour of the cast shadow lighting matches the colour of the translucent material, lower in contrast.

Luminescence is where the surfaces glow and emit light, while not receiving cast shadows. The lower the strength of coloured light the more of its colour is visible, gets brighter then goes to white. Integrating the light emitted by illuminating some neighbouring surfaces.

Water has both reflection and transparency being more transparent in the foreground than further away.  The observer’s sight lines bouncing off the surface, when it is smooth it is more like a mirror with a fresnel effect or glass, looking straight across it.  The reflection is less transparent where the sight lines become more tangent to the surface.  The rougher the water the more diffuse and softer the reflections edges will be to the point where they can disappear, the reflections are more distorted or stretched and cover a larger area.  Muddy water at dusk will reflect just as well as clear water.  Looking directly down onto the water’s surface it will look darker and not much light from the sky is seen.  A wet surface is like a water coating  Think of the roughness of the surfaces, depth of the water and the reflections can change over the surface where a rough surface is like rougher water and smooth might have smaller, crisper reflections.  Cast shadow on water work with sediment and their edges are more diffuse than on land. In mountain streams, the warm colours of the shallows and blues and greens in deeper pools, there is also the green colour of the trees and the slue from the sky reflecting off the water.  What about underwater?  Water attenuates light due to absorption which varies as a function of frequency. In other words, as light passes through a greater distance of water color is selectively absorbed by the water. Color absorption is also affected by turbidity of the water and dissolved material.  It happens over distance both down and across with impurities discolouring the water in different ways.

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection.

Transparency is the physical property of allowing light to pass through the material without being scattered.

Caustics is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface.  Transparent objects with the caustic effects clustering inside the cast shadows. Under water caustics occur not much deeper than 20 or 30 feet and on sunny days being visible on top surfaces. Caustic reflections almost anywhere the sunlight shines through curving glass, water acting like a concave mirror or reflects off shiny metallic surfaces.

Colour corona or lens flare forming around any very bright source or reflected source including streetlights, car headlights and solar highlights on wet surfaces. The glow takes on the native colour of the source.

Greens can be mixed from blue and yellow, use pink or reddish grey and weave with the greens, Smuggling Reds with Stapleton Kearns 

Light decay for a strong mood have strong decay

http://rom-ko.blogspot.com.au/2015/05/return-to-fundamentals-6.html

Spheres as an example for different lighting.

Sunlight, as it rises it scatters blue spectra in the atmosphere and lets the reds and yellows pass through, colour temperature 3000K to 4000K in the early morning.   Sometimes it is a pale tangerine light that breaks on the horizon an slowly becomes a bright yellow as the sun moves higher becoming a yellowish-white sunlight.  The colour balance of daylight around the middle of the day is 5000 – 6000K with the time of day affecting the exposure and the colour temperature.  Need to consider the areas between the highlight and the shadow, sunlight wraps around objects with only the sides directly opposite the sun that are completely dark, what are the shadow edges doing.

Moon light is reflected sunlight, colour temperature the same as sunlight and the moon acts like a huge grey cared that is neutral in colour.  We perceive blue because of the low light levels.

Direct sunlight, the passive highlight being the true value and the core and cast shadows being halfway to black and have the reflected light off the ground creating an effective core shadow wrapping around the sphere’s terminator.  Wrap the value shading around the minor axis that points from the centre to the sun.  Direct Sunlight has the sun, the sky which is diffuse soft light and reflected light from illuminated objects.

Overcast Light reduces the dramatic contrasts of light and shade, colours appear brighter showing patterns staying constant throughout the day, very diffuse and a colour temperature around 7600K to 8000K.

Side sunlight, change in position of the core shadow being wider on the shadow side and the shape of cast shadow and is symmetrical. Maintain the correct relationship of the minor axis for the core shadow and the passive highlight location.

Direct local light, the core shadow can become wider than in direct sunlight as it is further from the reflected light source, the ground. The cast shadow receives less ambient light and is darker than the sunlight cast shadow.  Local light with light coming from a  single point, the angle of incidence changes over distance. Shadows can go from light to dark with extremes of fall off, include on object surfaces.

Side direct light, be mindful of the falloff on both the ground plane and the sphere, the ground shifts to nearly black and the cast shadow has a value structure darker than halfway to black. The reflected light off the ground reaches a little past the equator cut line of the sphere causing the core shadow to disappear in the half facing on the shadow side of the sphere.

Window Light, not direct sunlight, the daylight is usually bluish and mixes with the orange colour of artificial lights. The bounced light from the ground reflected on the ceiling.

Indoor Electric Light, incandescent and fluorescent.  Consider Brightness or relative brightness depending on wattage, type of lamp, proximity to the subject and how bright the other lights are. Hard, which is more directional and dramatic with a crisper shadow bringing out more surface texture or Soft light that creates a wider area with softer shadows. Colour Cast in Kelvin, being the dominant wavelength of the light source.  Incandescent are strongest in the orange and red wavelengths and weak in the blue. Warm white and cool white fluorescents emphasise yellow-treen.

Spectral Power Distribution Curves

Streetlights and Night Conditions moonlight which appears blue or grey.  There are a large variety of night lights, incandescent fluorescent, neon, mercury vapour, sodium, arc, metal halide, led lights. Suggestions, use a camera on night setting, disable white balance and take photos of the colour wheel under different lighting conditions, use a led light to illuminate my palette when painting at night.  Moon light is the sunlight reflecting off the grey surface.

Luminescence, not Incandescence which is hot or flaming objects giving off light, giving off their own lightened can graduate from one hue to another. Fluorescence with objects when lit by ultraviolet light.

Atmospheric optics deals with how the unique optical properties of the Earth’s atmosphere cause a wide range of spectacular optical phenomena.

Outdoor environments have the sun or moon as the light source and has gradation which is darkest straight up and lightest at the horizon being colour depends on the time of day.  Need to think about where the line of sight bounces off the form into the sky and think bout the value and colour the sky is at that point. The contrast between the object and the sky affects how much of the reflection of the sky is seen in the object and this could be where there are shadows, an illusion of the cast-shadows being more reflective.  There is solar glare governed by the proximity to the sun and horizon glow which depends on the angle above the horizon.

On a clear day with clear air the sky is more blue-violet and the shadows are darker and bluer relative to the sun. With more clouds the shadows become paler and with more haze or smog the shadows appear relatively closer to the tonal value of the sunlight. With fog, mist, smoke and dust the contrast drops off rapidly, the sun cannot penetrate and forms recede in space.

Toward the sun clouds have dark cents and light edges with the sky being a more dull grey-green.  Away from the sun, shinning from behind the viewer,  they are lightest at the tops or centres and get darer at the sides and bases and the sky the blue is higher in saturation and more towards violet, looking completely different.  Smaller clouds are not as white. Rayleigh scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the blue color of the sky and the yellow tone of the sun itself.

http://animationtidbits.tumblr.com/post/29846146240/diy-001-drawing-101

Solar glare making the sky lighter and warmer nearer the sun with a noticeable lightening at the anti solar point which is 180º opposite the sun.  The sky getting lighter as we move from zenith to horizon, the horizon glow, because we are looking through more atmosphere. The darkest, deepest blue called the well of the sky is at the zenith only at sunset and sunrise. It is 95º away from the setting sun across the top of the sky. At other times in the day, it is about 65º away from the sun.

Atmospheric Perspective or perceived depth of how objects appear as they are views in the distance, further away having less value. this changes on a cloudy day, if there is moisture, dust, haze, smog or if it is illuminated.  The contrast shift between the light and dark values with less colour saturation than surfaces that are closer.  Strongest at the horizon as has more atmosphere, looking straight up has less then looking further away such as the horizon.  White and black objects  are different, them becomes warmer in colour with oranges and reds of the setting sun. Clouds are also affected, becoming more orange and darker near the horizon eventually merging with the sky at the horizon. White objects remain visible the longest. Generally warm colours advance and cool colours recede and in reverse atmospheric perspective the rule is reversed, such as at sun rise or sun set on a misty or dusty day.

The Golden Hour where the light travels almost parallel to the surface of the earth, travelling through more atmosphere making the sky bluer with forms lit by this light are more golden and shadows bluer. If the air has moisture and dust the clouds will take on more colour with the boldest where the sun crosses the horizon, the higher clouds are whiter  being pinker for sunrises.  A weaker glow at the anti solar point then after sunset a grey layer raises up from the horizon being the cast shadow of the earth.  Remember the colour of the earth below, it is not black.

Not all materials respond to light the same.  Clouds vary in density, thickness and composition where there an be a definite light and shadow side.  Clouds transmit a greater quantity of light to the shadow side through internal scattering than the volume of light they pick up from secondary sources. Trees, foliage, hair, glass, metal.

Sunbeams or Crepuscular rays in atmospheric optics, are rays of sunlight that appear to radiate from the point in the sky where the sun is located. These rays, which stream through gaps in clouds (particularly stratocumulus) or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions. Despite seeming to converge at a point, the rays are in fact near-parallel shafts of sunlight, and their apparent convergence is a perspective effect (similar, for example, to the way that parallel railway lines seem to converge at a point in the distance).  There needs to be a high screen blocking most of the light, a darker backdrop with a few openings, a view toward the sun, going through some dust, smog or similar and influences the value of the shadows more than the light side.  Sunbeams, small areas of atoms being illuminated and edges of cast shadows of clouds.

Shadowbeams, a bar of unilluminated vapour seen edge-on, the adjoining illuminated air is slightly lighter in value and usually only visible when there is a light hazy sky behind.

Rainbows are a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.  Created from rain droplets after a storm, it does not occupy a particular geographical space, it is an angle in relation to the viewer. The primary rainbow forms at about 42º from the anti solar point.  As the sun descends the anti solar point rises from below the horizon towards the horizon. The anti solar point is at the centre of the rainbow and all shadows need to be oriented to that point. A secondary rainbow is the reverse colour and weaker and the sky is slightly darker between them. Alexander’s band or Alexander’s dark band occurs due to the deviation angles of the primary and secondary rainbows. Both bows exist due to an optical effect called the angle of minimum deviation. The refractive index of water prevents light from being deviated at smaller angles. The region between them the sky appears darker. The rainbow colours are lighter than the background. Even curvature.

http://www.handprint.com/HP/WCL/perspect6.html

Sunlight direction and shadow construction is parallel and parallel lines in perspective have a vanishing point. Light rays share a vanishing point. Long when close to the horizon. Positive Sunlight, above the horizon and back lit. Negative sunlight which is below the horizon and front lit.  Sunlight always has a constant angle of incident giving an even value over a surface. When the form changes the light’s rays change angles of incidence and the values change.

https://hea-www.harvard.edu/ECT/Latitudes/latitudes.html

http://www.powerfromthesun.net/Book/chapter03/chapter03.html

Light Plane is the direction of light, being the direction of shadows and the length of shadows.

http://juliannakunstler.com/art1_shadows.html#.Vxx3dMcSD8s

Lighting Ratio of the lit side and the shadow side.

SHADOWS

The recognition and understanding of how we see colour enables us to create emotional lighting through the use of colour, which is dependent on lighting and affects the way we interpret the image’s emotional content.  We need an understanding of how the light source affects objects.

When an object obstructs the light and does not let it pass through partially or totally it creates a shadow.  The penumbra is the area of the shadow that is partly illuminated and partly occluded, generally lighter in tone than the darker central area. Umbra is totally occluded area of the shadow that has no illumination, mostly dark in the centre with a gradual tonality change as it merges with the penumbra.

The shadow position gives us spatial orientation based on information about the depth of objects, their size and form, depth perception.  The position of the shadow is also used for evaluation of textures, material density and composition.

https://knowledge.autodesk.com/support/3ds-max/learn-explore/caas/CloudHelp/cloudhelp/2016/ENU/3DSMax/files/GUID-C192817F-0A1E-4348-9AFA-A1DC450A0FD1-htm.html

The shadow value is halve the value between the true value and black and shadows use the ground or shadow surface true value.  White is one and Black calculated as 10.  The object and ground have different true values. Darker objects have less range to work with.  Ambient light, the halfway-to-black occurs again. Not in direct light then consider the light ray angle.  Avoid linear graduations in the shadows and occlusion as it gets to the core-shadow.  White looks different outdoors than indoors with fluorescent light.

Small light sources have hard-edged, dark shadows with almost no detail, no middle tones and with a very bright and small highlight.  The penumbra generated by the small light source blends with the umbra. It is directional and indicates the orientation of the light source such as a sunny, cloudless day or far away spot light.

Medium light source is directional, soft, diffuse, light mid tones with less separation between light and dark areas such  as window lights, covered overhead ceiling lights and diffuse incandescent lights.

http://bluesky.photo/tutorials/lighting-theory-8/

Large light source, no dark shadows, very diffuse, light envelops the object, no penumbra and umbra separation, orientation difficult to determine, highlights are spread out and blended together such as an overcast, cloudy sky.

Cast Shadows are flooded from various sources, it is when direct light is intercepted by an object that casts a shadow. On sunny days they tend to be more blue and on partly cloudy days they are whiter.  Observe the edge quality of shadows and the light source creating them.  The edge of shadows gets softer as the distance increases from the object that casts the shadow. Consider how the shadows are cast and how the tonal values are compressed, the full tonal range is there and becomes dominated by one tone.

Some different types of shadows such as Two side-by-see lights will cast two side-by-side shadows.  Shadows on snow pick up the colour of everything around it and has subsurface scattering with back-lighing showing more taking on blue-green hue as the red is absorbed. Half shadows creating part shadows on objects which could be from something far away.  Where is the shadow, foreground, middle or background.

Dappled shadows of light passing through small spaces creating varying size shadows considering the distance between the object and the shape of the object where the shadow is. The sky holes are not necessarily uninterrupted views of the sky, lessens the amount of light coming through from the sky giving the sky a darker colour.

Cloud shadows have soft edges and take some distance to happen, match the clouds in the visible sky with the shadow area being darker and cooler than the sunlit area with not as much blue cast as a clear day. It is a mixture of the sky blue light and the diffused white cloud light.

Occlusion is shadow light being blocked by neighbouring surfaces such as corners, crowding out the light leaving small and dense areas of shadow.  It is usually  the darkest part of the shadow, creating dark accents.

Specular reflections from shiny surfaces of what is around it.

Highlights are specular reflections of the light source on wet or shiny surfaces.

Reflected light will often increase the tone of a shadow.

Luminance contrast giving depth, how to see the shape and depth from the shading. Does not matter what colour the shadows are so long as the luminance is right.

Shadow Edges, the sharpness indicates how far away the object is from the cast shadow.

• long such as from the top of a light pole to the ground, soft
• medium would be from the top of a stool to the ground
• short would be from the top of a cube to the top of the stool, sharp

The shadow edge can transform from hard to soft. Perspective foreshortening also sharpens a shadow’s edge WS, CU.

http://rom-ko.blogspot.com.au/2015_01_01_archive.html

Curved surfaces usually do not have edges to define shadows.

• light side is the direct light.
• shadow side is not exposed to direct light and usually receives reflected or ambient light.
• terminator is between the light and shadow side, it position is determined by the tangency of the light rays to the surface.
• cast shadows from the terminator to ground plane.
• core shadow when ambient and reflected light is affecting the shadow side of an object.  The reflected light is bouncing off the ground plane and lighting up the shadow side.
• occlusion shadow occurs where the object makes contact with the ground.

https://www.pinterest.com/pin/452471093785384362/

The core shadow jumps when the tapering angle of a cone changes.

Avoid adding dark values to the surface to create contrast, use a background value instead for stronger silhouette.  Adjusting the values of the background extends the illusion of the range of values of the object in the foreground.  Can control which areas of an object appear lighter or darker.  To make an object look brighter put on a dark background, to make it look darker put on a lighter background.

Cut lines or panel lines, part lines, shut lines, thought of as two edges and the way light catches these edges.  The brightest spot of the highlight is where the light strikes at 90º to the direction of the part line, if it is from above it it illuminates the bottom edge of the part line and the top edge drops into shadow. As a part line wraps from the light side of an object to the shadow side, the edge highlight fades to no light with an exception being when a strong, reflective light source makes another highlight fade in a different direction.

Textures are the physical roughness of a surface being indicated by changing values and the reflectivity of the surface.  Lighting changes over the textured surface showing the textures differently.  Linear and atmospheric perspectives make textures int he distance appear flatter.

Matte surfaces, the true value is the physical colour of the object. With a matte surface they would be lighter towards the top where the surfaces are more perpendicular to the light and darker on the sides were they are more tangent.

Highlights are the brightest area and there can be both a reflective and a passive highlight on a matte surface.  Both can be visible though not necessarily matching with position and located on different areas on the surface.  The passive highlight stays in the same position relative to the light source while the reflective highlight moves when the line of sight’s angle of incidence changed into the surface.  It is important to note the shape of reflections.

Reflected or bounced light is how objects affect on another from a shiny car to a wet surface with a stronger influence on the shadow side due to the absence of direct light.  It can bounce more than once illuminating soft light back into shadows. Reflective light can lighten core shadows interacting evenly with objects and environment.  Surfaces that are in shadow and face downward towards a reflected light source can actually be lighter than upward facing surfaces within the same cast shadow.

The form of any shiny object is communicated by varying the strength of the reflections of the surrounding environment, it is not to do with where the light source is coming from.  They are the reverse of matte surfaces the less shiny areas show more body colour, while the shiner areas there is more of the chrome look, getting skinnier.

Shiny surfaces are sensitive to small scratches and are most obvious in the reflection. The reflections on a shaped surface may be reflection different parts of an environment such as buildings, landscape, sky and/or ground, thus returning different colours on the same object.  Think about designing the environment to enhance the scene’s reflections and the form of the objects.

http://www.inpursuitofart.com/blog/lessons-how-to-render-scott-robertson/

Angle of Incidence is the angle that the line of sight bounces off the shiny surface into the environment with the line of sight’s angle of incidence is always equal in-equal out – the line of sight. The angle at which a line of sight hits a surface is exactly the same as the angle out which it bounces away from the surface.  The line of sight will bounce/reflect off the chrome form, into the environment around it. The reflections are what surrounds the reflective surfaces. The horizon line is reflected in the surface where your line of sight bounces off of the surface parallel to the ground plane. When the surface is curved the light bounces off into different parts of the environment, concave stretches and convex compresses.  Where the line of sight will bounce off the reflective surfaces into the environment.

When light bounces off a shiny concave surface we get reflection flipping, where the sight lines bounce back to the same point. It is about the sections of the surface and where the sight lines bounce.

Mr Pittman’s Science Class

Concave mirrors (like the inside bowl of your spoon) can flip your image upside-down, but if you are really close it makes you appear right side-up and larger!

http://www.dailymotion.com/video/x3jyupe

harrisonscience Uses of Energy

Robertson, S., 2014. How to render: the fundamentals of light, shadow and reflectivity. Design Studio Press, Culver City, CA. page 165

The lighter the value the less the perceived reflection, our brains the amount of matte surface eases reflective surface differently.  The same reflective surface and environment for a white and black ball, the white ball the brain perceives mostly matte surface with little bit of reflection, seeming to have a strong core shadow.  Our brain perceives a very shiny surface with just a little matte surface for the black object,  meaning no core shadow on the light side is visible on the black ball. For a middle-value colour like red equal amounts of matte surface and reflection are perceived.  The light values shining off the black ball appear as white on black and on the white ball are white on white.

Shiny surfaces become a mirror of their environment, when they overlap and touch they become the same colour and value of that surface. If this is not want I want then possibly dull down the surface.

http://www.scratchapixel.com/lessons/3d-basic-rendering/introduction-to-shading/reflection-refraction-fresnel

Introduction to Shading Reflection, Refraction (Transmission) and Fresnel

The “Fresnel Effect” describes the amount of reflected and refracted light that we see on an object depending on the angle form which it is viewed.  An effect we will see on everyday objects, including skin.  Look at something at eye level, tilt away and notice the reflection at the grazing angles – this is the effect of Fresnel.

On all surfaces other than chrome, the strength of the reflection changes based on the line of sight’s angle of incidence into that surface.  The strength of the reflection of the environment changes and grows stronger as the surface rolls away from the line of sight. When the line of sight is perpendicular to a surface, which would be the centre of a sphere, the reflection is weakest.  When the light of sight cases tangent to a surface, the reflection is strongest. Chrome is the exception and is 100% shiny from any angle.

Vary the strength of the reflections due to the angle of incidence. Remove the reflection where the line of sight is perpendicular, this is where the reflection is least shiny and where the line of sight is tangent to the form, leave the reflection layer more opaque. Where we see a gradation change across a surface we see a form change.

http://www.racer.nl/blog2008.htm

A black car, the parts that are perpendicular to your line of sight will appear less shiny, more matte than the areas where the angle of incidence of my line of sight is tangent to the car’s surface. A light road reflecting onto a dark car provides the most contrast.  When looking straight at the surface the line of sight is bouncing in all different directions of any irregularities. When looking tangent to it, the irregularities align and many more of the sight lines bounce off the surface in the same directions causing the Fresnel Effect.

Thinking about waves, the front of each ripple facing the viewer and the back of each ripple causes variations in the strength of the reflection which results in a value change, thus the brain perceives a form change.

http://www.3drender.com/glossary/fresneleffect.htm

In addition to how hard or soft a reflection is, the amount of reflection on most objects will change depending on the angle you look at it. This is achieved in the 3D environment with the use of a Fresnel layer applied to the texture.  https://photoreal3d.wordpress.com/category/photorealism-in-3d-cgi-imagery/fresnel/

With water looking straight down it looks more like its true colour and while looking out across the water, it becomes brighter and brighter, more of the light colour of the sky.  The same for glass.

Renderosity: Glossy materials with true Fresnel effect using matmatic

The observation that the amount of reflectance you see on a surface depends on the viewing angle.  As shown in the renders above, if you look straight down from above at a pool of water, you will not see very much reflected light on the surface of the pool, and can see down through the surface to the bottom of the pool.  At a glancing angle (looking with your eye level with the water, from the edge of the water surface), you will see much more specularity and reflections on the water surface, and might not be able to see what’s under the water.  http://www.3drender.com/glossary/fresneleffect.htm

Mirror, if it is clean has no cast shadows because all the light striking it is reflected away. If it is dusty, a light shadow starts to appear.

MATERIALS

The materials properties are how the surfaces interact with light.

Specular vs Diffuse, if 80% of the incident light reflects as specular 20% reflects as diffuse.  If 60% of the reflected light is diffuse then 40% will be specular.

Matte has a dull, rough finish spreading light equally having almost no specular depending on the orientation of the material it can reflect highlights and diffuse illumination on other surface.

For shiny nonmetal objects the specular colour is white and for metals it takes on the colour of the metal. There is the movement of reflected environments on glossy and reflective surfaces which can be difficult to light maintaining their own form and shape particularly with light or dark backgrounds.

Generally solid objects have a wide tonal dynamic range having white highlights and some dark greys or black.

Semigloss with the amount of texture affecting the sharpness of reflections, with reflections where the sight lines are most tangent.

Transmissive objects always have limited tonality not representing both ends of the tonal spectrum.

Since light gets scattered and absorbed not all the energy would be present in the reflection with highly reflective objects having minimal diffusion.  Specular reflection does not always have to be sharply defined.

Glass is transparent, usually shiny and it both reflects and refracts. Glass has the ability to both reflect the environment as well as blend into it.  The fresnel effect of whatever is behind is least visible where ever the fresnel effect is strongest an most visible where the reflection is weakest. When it is further away there is less fresnel effect and larger reflections as the sigh lines are becoming more parallel.

Refraction is a change of direction of a ray of light creating distortion, the bending of light as it passes from one medium to another.

Metallic paint’s reflection could be multiple soft reflections across a larger surface area reflecting less of the surrounds and more of the light, increasing the value change across the surface. The clear coating will have the sharp reflections of the light.  Reflects the environment the way metal would with less specularity and muted reflection.

The curvatures of the sections control the width of the reflections of the light source, chore shadow and distortion of the environment while the flatter or softer sections reduce the gradation changes.

Chrome has no matte-surface qualities, no core shadow, no light side, no shadow side and reflections stay sharp, gradations happen because they are in the environment.  It is usually one-half to one full value step darker than what it is reflecting. Take everything from around the object, drop on the surface and then the whole layer can be darkened.  Let it blend in a bit to the background and reflect the colours and values of the environment accurately.  There is no fresnel effect.

Metals such as brushed metal have a series of very small, aligned scratches, anisotropic, which are most visible next to where the light’s reflection is strongest, stretching the reflection. Machined metals can also show anisotropic qualities, the ability to change the amount of reflected light as the viewing angle changes, anisotropic reflections which can be sharp or blurred.  Aluminium can have a matte surface or polished like chrome, the more matte it is the less reflective it is.  Most metals can vary depending on age, polish, exposure to the weather and quality.

Isotopic objects that reflect equally as the viewing perspective is changed.

Wood think about the grain, colour, values and levels of reflectivity.

Leather and cloth think about the design, context, construction, textures, reflectivity.

Carbon fibre weave and how it reacts to light, usually only one of the directional rows reflect the light source while the other row looks darker and look at the fresnel effect.

Textures are most visible on shiny surfaces where the light source is reflected and on matte surface, not on the main highlight, other areas such as just before the core shadow on round objects.

Camera effects such as motion, bloom and glints can add more personality and life to my renders along with the effects of weathering.  With motion blur, what is moving, the camera, the object and how is this movement creating motion blur?  Bloom creates fringes or feathers of light extending outward from the centre of the bright areas of an image across the borders of these areas giving the illusion of a very bright light. Glints, like blooms, are reflected at an angle from a surface in the form of highlights, to give off reflection in brilliant flashes. 

Motion blur is the apparent streaking of rapidly moving objects in a still image or a sequence of images such as a movie or animation. It results when the image being recorded changes during the recording of a single exposure, either due to rapid movement or long exposure.

With Relative Motion near objects seem to move more than distant objects.

Bloom (sometimes referred to as light bloom or glow) is a computer graphics effect used in video games, demos and high dynamic range rendering (HDRR) to reproduce an imaging artifact of real-world cameras. The effect produces fringes (or feathers) of light extending from the borders of bright areas in an image, contributing to the illusion of an extremely bright light overwhelming the camera or eye capturing the scene.

physics of color in glints

Depth of field is the distance between the farthest and nearest objects in a scene that are both in focus.

When rendering the surface could be chasing form in all directions so concentrate on key points, considering the continuation of the shape under the surface or off the area.  There might be no visible area that has the true value of the object since none of the surfaces are perpendicular to the light rays.  Concentrate on the orientation of the surface towards the light source.  Observe that both the round and the object are affected by the light’s decay.  Remember the reflected light within the shadow side and it communicates the form of the shape’s surface, even within the shadows.  Remember to assign similar values to surfaces that have the same orientation to the light source.

Adding colour, choose the colour that will appear on the mainly lit area, know the value and not the value of the grey in the same area. It is not necessarily the value of white at 1, white point. This white point many need to be darkened down to something closer to represent the values, making the adjustment to darken the value for the desired colour. The white might be the equivalent to a 20% grey or even 50% grey.

Show the colour and the material.

Workflow Approaches

• know my environment, surroundings
• start with all in grey scale getting the forms working by focusing on changes in value, matte values
• design and place lights, the light direction and primary light source, including the position of the sun for outdoor scenes
• start with the largest volumes and adjust the overall proportions and the lighting
• how each area will be lit, looking at light rays
• headlights, wheels and some smaller forms by adding a new layer and seeing how new forms can be created
• shadow area and shadow placement
• colorise the grayscale matte surface and add details
• details like exhaust vents, levels adjusted, bright spots starting to take on the metallic look
• rim lights
• edges against each other, possibly disappearing into the other
• ground plane
• reflected light and in the shadows
• fresnel effects
• reflection of the sun thinking about the time day, colour or value of the sky and shape
• masks
• background refinement
• final adjustment layers
• consider prioritising matte-surface rendering for light values and reflective rendering for dark values. Red being the hardest with equal amounts of matte-surface and reflectivity. Matte surface underneath reflections show more value change on a lighter-value surface than on a darker on.
• simplifying and controlling the environment can help work get done more quickly
• render the reflections of a light source separately from reflections from the rest of the environment and also cast shadows on reflective surfaces

Workflow Approaches

• Motivation of the scene, miss-en-scene
• Planes of light, levels of illumination for foreground, mid ground, background and subjects giving tonal relationships that create depth both locally and globally
• Colour, direction, reflections, visibility of objects, type and quality of light and shadows
• Study and analyse the subject using one light
• Position the key light
• Change the intensity or move the key light
• Add a fill light
• Add a backlight/rim light
• Add kicker light
• Add other lights including character lights and object lights
• Modifications

Joon Ahn

Thomas Bertling

Tianxu (Tim) Guo

Charles Liu

Gadget-bot

Neville Page

John Park

Chen Xiao Quing

Scott Robertson Draw Through, Draw Through Blog, Youtube

Robh Ruppel

Robert Simons

Baoqi Xiao

Shadow In Perspective Drawing- Art Technique

Below are copies of parts of posts made to DLF in December 2015 which I thought were interesting. The most recent is at the top.

Color Profile: Linear sRGB

See the next section for more.

This from the Autodesk Help Files….
“Scalar or single channel texture images intended for bump, normal, displacement or other non-color applications should select Linear sRGB as their Color Profile under the File node Attribute Editor.”

Again we can look at this image, anything with a cross on it should have it’s color profile set to…

Color Profile: Linear sRGB

5. Check Bump/Normal/Displace Linear Workflow

Bump, normal and displacement maps (and some other) file types need to be changed to “linear srgb” in the file node for each file texture.

So for each bump/displace/normal texture we need to change their default type to linear srgb.

This is found in the file node of your textures. Change “Use Default Input Profile” to…

Color Profile: Linear sRGB

We need to remember this for all Bump/Normal/Displace file textures!!

This from the Autodesk Help Files….
Scalar or single channel texture images intended for bump, normal, displacement or other non-color applications should select Linear sRGB as their Color Profile under the File node Attribute Editor.)

Again we can look at this image, anything with a cross on it should have it’s color profile set to…

Color Profile: Linear sRGB

CHECK LINEAR IMAGES OUTSIDE MAYA

To check a linear image outside of Maya the easiest program to use is

imf_disp

32 bit images are also supported by almost all major compositing programs including Photoshop, After Effects and Nuke etc. Each program has it’s own way of dealing with 32 bit images and linear color management.

imf_disp

This program comes with Maya and is a Mental Ray Tool to check renders.

1. Load imf_disp (on mac you can open through the spotlight)

2. Open your rendered image by browsing to it. Never save an image from Maya’s Render View “File > Save Image” Do not use this!

Images in the Render View are automatically saved to

images/tmp

So get the images from there, or render with Batch render like you would rendering an animation.

4. Change the gamma
If we are using linear 32 bit workflow our images will come in too dark. Adjust the gamma to 2 in the upper right of the image window. Now we’ll be seeing the image correctly outside of Maya.

5. Render Layers in imf_disp
imf_disp also supports viewing the render layers of an .exr file. To view layers go

Layer > (select the layer you’ll wish to preview)

After Effects Notes
We’ll be wanting to work with Linear workflow. This is very easy to setup in After Effects.

Click the number at the bottom of the project tab. should be something like 8 bpc. We’ll want to change that to 32 bpc, if using .exr images and linear workflow in maya. (see here for the maya linear workflow settings)

We also want to check the box “Blend Colors Using 1.0 Gamma” So we can view our images in normal sRGB color which our monitors are.

Viewing .exr Layers in After Effects
Unlike in Nuke .exrs are not supported well in After Effects.

It’s best to download a free plugin which helps us manage .exrs in After Effects.

The following tutorial show’s how to use exr’s in After Effects. I’ve also noticed that when extracting using proEXR you must also convert each extracted comp to linear color…

Effect > Utility > Color Profile Converter (check “Linearize Input Profile”)

http://youtu.be/StqSiJ46O4Y?t=8m5s

http://forums.cgsociety.org/archive/index.php/t-966210.html

MR LIGHT SETTINGS – BASICS

1. Make our scene is at correct scale, 1 unit = cms

2. Directional Lights are mimicking sun or moonlight, so these lights won’t have any falloff because they are so far away we’ll never notice the drop off.

3. For lights other than sun/moon will have a light falloff, just like in the real world. The physically correct setting in Mental Ray is in the light settings…

Decay Rate to “Quadratic”

These lights will need much bigger numbers as values, up to 5000 or more. These are lumen values I believe, mimicking the real world.

4. Mental Ray is a Raytrace Engine
MR is a Raytracer, depth map shadows don’t work well with MR. Depth map shadows are for Viewport 2.0 or the maya software renderer. Raytracing is much more physically accurate anyway.

Switch all lights to raytrace shadows, no depth maps.

5. Blury Shadows
If we want blurry raytraced shadows on lights, usually spotlights or point lights (sometimes directionals) we change…

Raytrace shadow attributes “Light Radius” to a larger angle

Light Radius = Blur Amount as an Angle Value
Shadow Rays = make the shadow less grainy. Can be values of up to 50 or more.

To clarify Mental Ray isn’t as bad as everyone suggests, it’s certainly not as developed as VRay but in 2016 it’s pretty easy to use and teach.  The MILA shaders are my favourite shaders of any renderer.

Most of the MR bashing comes from when it was a nightmare to use and the kids didn’t know how to use it so peppered the forums with “MR sucks posts”.  If you ever speak to real lighters they always would say, MR is ok.  Pre 2016 the MR setup of proper linear workflow was a nightmare to teach and it was also for a long time quite difficult to set the lights up correctly, about 3 checkboxes in strange places.  So newbs and most instructors would never figure it out and say it sucks. It did suck for it’s complexity, agreed.

Since 2016 it all works out of the box and is easier than most other renderers now.  Not that it’ll make much difference to it’s popularity.

AO isn’t really needed if using MR properly with the correct bounce light FG or irradiance particles or whatever. AO in modern lighting is a bit of a no no.
Search MR vs VRay and there’s a difference but it’s minor.  VRay is agree to be better but MR’s fine.  Renderman is the other free renderer and is awesome for direct light and big area lights. IMO way better for character turntables.   Renderman can suck for proper window lit interiors due to very slow render times.  Arnold is similar with slow times on interiors and bounce light but awesome for area lights… unlike MR and VRay which have trouble with big area lights. Pros and Cons.

https://www.google.com.au/search?q=mental+ray+vs+vray&espv=2&biw=1497&bih=958&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj7rYy4jeTJAhXXC44KHUA9AeEQ_AUIBigB&dpr=1

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I’d re-render the turntables in Renderman RIS, they look much better that MR turntables, try learning Renderman it’s very easy and free. Interiors are still nice in MR, but those character turntables Renderman is much better straight out of the box and you get that lovely look. Arnold is good too but watermarks in the free version.   There’s loads of little things you can pick on otherwise but nice work!

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To clarify Mental Ray isn’t as bad as everyone suggests, it’s certainly not as developed as VRay but in 2016 it’s pretty easy to use and teach.  The MILA shaders are my favourite shaders of any renderer.

Pre 2016 the MR setup of proper linear workflow was a nightmare to teach and it was also for a long time quite difficult to set the lights up correctly.

 

Since 2016 it all works out of the box and is easier than most other renderers now.

 

AO isn’t really needed if using MR properly with the correct bounce light FG or irradiance particles or whatever.

Andrew Silke

3d Animator and Instructor

www.create3dcharacters.com

www.facebook.com/create3dcharacters/

https://www.linkedin.com/groups/63979/63979-6372213319524249603?midToken=AQFs516VoK72wg&trk=eml-b2_anet_digest_of_digests-hero-12-view%7Ediscussion&trkEmail=eml-b2_anet_digest_of_digests-hero-12-view%7Ediscussion-null-2emuqb%7Eje50h51w%7E7s-null-communities%7Egroup%7Ediscussion&lipi=urn%3Ali%3Apage%3Aemail_b2_anet_digest_of_digests%3BabB1X9zwR2S%2FHZ0bYA9o7w%3D%3D