3D Lighting =========== Color Weight and Density (from lite to heavy) ------------------------ white yellow green blue orange red * cool tones for the background and warm tones for the foreground extend the 3d feeling of a 2d image. Colored Shadows --------------- The color of a shadow should be complementary to the key light. Materials --------- Mate ---- Has a rough finish. Acts as a diffuse reflector thus has a high ambient light at the surrounding area. Shiny Non-Metal --------------- Reflects only 4% of the incident light and the rest is given off as a diffuse. The specular color is white. Metal ----- * The modeled surface should be very smooth. Reflects more than 4% of the incident light. Reflects the environment. The specular color is the same as the surface color. Solid ----- Has a wide tonal dynamic range. Transmissive ------------ Has a limited tonality and do not represent both ends of the tonal spectrum. Reflection ---------- There is a diffuse reflection and specular reflection. The ratio between the two reflection types is always related at an inverse relation. Specular reflection has to be softened. Glass ----- Must have an outline along the edges. If the background is dark the outline should be light and vice versa. Local Illumination ------------------ Direct light illumination, from a visible light source, and reflections. Global Illumination ------------------- Indirect reflected light transfer in a scene. Implemented as two models: Backward Raytracing (from the eye to the object) ------------------- Calculates the ideal specular. Assumes that all the surfaces are ideal specular reflectors. View dependent. Radiosity --------- Calculates the ideal diffuse reflections. Assumes all the surfaces are ideal diffuse (the Lambert shading model). How much energy is exiting a particular point on a surface. Embedes to the scene geometry's vertices and thus enables quick generation of new perspectives. Requires a lot of RAM and HD space for the files. View independent. Radiosity is interpolated across a polygon thus the geometry should be quad based (no triangles) to get correct results. T-vertices should be avoided. (Vertices that reside on a median of a polyline between two elements). Shading Models -------------- Simulation of the way the light affects the object's own material. Ambient ------- Mimics the object to object light reflection. Constant -------- A single shade for the whole object. Gives no 3D dimensions. It's the most primitive shading. Flat ---- Per-polygon shading. Gouraud (named after Henri Gouraud) ------- Used for mate surfaces. Computes the intensity for each vertex and interpolates the color across the polygon. Not good for specular reflections. Phong (normal vector interpolation shading) (named after Bui Tuong-Phong) ----- Simulates glossy and shinny surfaces. Enables to change the size of the specular reflection but it's color depends on the light source. Lambert (cosine shading) (named after Johann Heinrich Lambert) ------- Simulates dull, smeared, mate surfaces. The incoming light reflected equally in all directions (the reflection is independent of the viewer's perspective). Blinn (named after James Blinn) ----- Implements realistic specular-to-diffuse reflections. Has a self-shadowing, specular reflections and edge specularity. Light Arrays (function as a single light source) ------------ Central light : The hot core of a direct illumination that dominates the scene. Peripheral lights : Edge illumination colorants. Each peripheral light should have the most 50% the power of the central light. The overall power of all the peripheral light should be lower than twice the power of the central light. Dual (2 lights) ---- Both placed at the same spot. One is used as a shadow casting source and the other lightens the shadow and completes the illumination. The overall light intensity of both light sources should be 100%. Diamond (7 lights) ------- The main light is placed in the center and the peripheral lights arranged in a diamond shape around it. The main light has the highest intensity and it gives the array it's dominant color. The peripheral light may be shadow casting or non-shadow casting. Pyramid (6 lights) ------- The main light is placed at center of the pyramid, 4 lights form the base and another light formes the apex. Dome (6-12 lights) ---- The lights arranged in a hemispherical way. There're two layers of lights and the apex light. It's a variation of the "pyramid" array. Ring (12-16 lights) ---- The lights arranged in a circular shape around a central main light. Box (5 lights) --- The peripheral lights arranged on the corners of a box while the main light is placed at the center. Tubular (9-25+ lights) ------- Many rings combined together. Artificial Lights ----------------- * The color of the middle tones and the highlights suggests the kind and type of the light source. Incandescent (makes light when heated) ------------ Incandescent bulbs burn at lower temprature than other types of lights, so they give off an orange-yellow light. Most of the time our eye doesn't perceive this light color as orange. It's simulated using omni lights or a 3D light array with the central light slightly whiter than the peripherals. Fluorescent ----------- White color lights that burn cool. Seen as white to pail bluish-white. It's actual color is blue-green and it's increases with distance. It's simulated using 3D light array with a central white light and greenish peripherals. Registers specular and middle tones as white. Middle tones become greenish when distance increases. Vapor-Filled (HID = High-Intensity Discharge) ------------ Produces an electric spark that vaporizes the metals, which then emits light. Affects the specular hightlights and the middle tones. Metal Halids ------------ An HID white light. Has a slightly bluish-white hue. Affects the specular hightlights and the middle tones. Sodium ------ High-pressure or low-pressure very bright lights that are used in illuminating huge public spaces. Emits orange-yellow or pinkish hue. Lacks blue-green spectra. Candlelight ----------- The surfaces closest to the candlelight are lighter than the surfaces far from it. The obstructed surfaces are very dark. The middle tones are desaturated and colorless. Use dual point light formation at the top of the candle. (LightWave: use 180% spotlights pointing down) Campfire -------- Use pyramid array to simulate the illumination near the base of the fire. The array can be rotated on it's axis to suggest intensity and color changes. Light Types ----------- 1. Key dominant light: A point light that illuminates the whole scene. 2. Direct light: The main light source. 3. Middle tones illumination: Has the same position as the direct light but is much darker and has low intensity. * White lights push the middle tones into the highlights region. 4. Indirect illumination: Light that bounces of the walls, floor, ceiling and other objects at the scene. 5. Ambient illumination: A point lights which are placed outside the scene and their attenuation range barly within the scene. 6. Inverse lights: Darken regions where there should be lower light or no light at all. Light Sizes ----------- Small Source (sun) ------------ High contrast. Far and unobstracted bright light source. Has a hard-edged dark shadows with a very bright and small highlight. A small penumbra blends with the large umbra. A directional source that always indicates it's orientation. Medium Source (window lights, diffuse incandescent lights) ------------- Medium contrast. Regional or localized directiolnal and diffuse light source. Has a soft and diffused highlights. There's subtle gradation between the light and the shadow areas. There is a distinct separation between the umbra and the penumbra. The umbra is light and the dark shadowed areas have details and form. Large Source (cloudy sky) ------------ Low contrast. There're almost no dark shadows and the light envelops the object. The highlights spread out and blend together. There's no separation between the umbra and the penumbra. Not a directional but a diffused source. Light Positions --------------- Front Lighting -------------- Evenly illuminates the subject and makes it look 2D. Good for minimizing wrinkles and making the subject look wider. Side Lighting ------------- 90* to the side of the subject. Emphasizes the texture of the subject. Reveals the form of the subject. Good for round faces since it's minimizing the roundness. * If the right side of the subject is lighted (as viewed from camera) it implies the subject is good natured and vice versa. * The faces are not symertical so high contrast light can create different look. Rembrant Lighting ----------------- 45* to the side and above the subject. Derived from the sun possition in late morning or late after-noon. Verry flatering and 3D. Reveals the form of the subject. Broad Lighting -------------- A variation of Rembrant lighting. On the same side of the camera. Good for making thin faces alongated and wider. Not suted for round or wide faces. Short Lighting -------------- A variation of Rembrant lighting. On the oposite side to the camera. Good for making round faces thinner. Top Lighting ------------ Above and slightly ahead of the subject. Forms deep shadows on a face. Emphasises bone structure. Good for glamour and fashion shots. Not suted for round or wide faces. Implies overcast daylight. Under Lighting -------------- Produces a mysterious and sinister feeling. Emphasizes the texture of the subject. Kicker Lighting --------------- Two key lights placed above and behind the subject. The shadows at the front are opened up by bounced or reflected light. Creates a highlight to outline the subject. Rim Lighting ------------ Accent lighting. Placed behind and slightly offset from the subject. Stronger than the key light. Draws attention to the profile of the subject (the profile is very bright). Good for glamour and fashion shots. Backlighting ------------ Accent lighing. Creates a strong highlight around the subject and dark shadows in the middle. Brighter than the key light. Good for melodramatic effect. Light Positions Based On The Time Of The Day -------------------------------------------- Midday ------ Very strong and high contrast. Use it when the contrast is naturally low. Water for example. The saturation of colors is very low. Late Afternoon / Evening ------------------------ Light gets warmer. The sky takes on a deeper shade of blue. Soft contrast. The sturation of colors is high. The shadows are near the complimentary colors of the highlights. Lighting Ratio -------------- Fill Lights ----------- Secondary lights in a scene. Control the illumination of the shadow areas and the contrast in the scene. Placed and turned on after the key light or the main light has been established. Supplementary Lighs ------------------- Incidental and situational lights. Placed depending on the script and the scene when a visible light required. Practical Lights ---------------- The lights sources that are explictly visible by the camera. Faking Radiosity ---------------- Place lihgt sources at surfaces that suppose to replect the light. This light sources should not cast shadows. Mood Light ---------- High-Key Lighting ----------------- The subject is evenly lit and there're almost no shadows. Used for sobjects that need to look soft and have glow. It implies overcast. The key light should be about one f-stop brighter than ussual. The key light and the fill light should be almost the same intensity. Low-Key Lighing --------------- High contrast scene. Used to lit men faces to sculpt the facial details. Strong key light dominates the fill light.