{3D illumination & rendering applications}
Global Illumination {GI}
Global Illumination is the general category for a suite of algorithms that are used to create more photorealistic lighting in digital scenes. GI incorporates all combinations of direct (specular) and indirect (diffuse) illumination to produce more realistic results.
Examples of different global illumination algorithms:
- ambient occlusion
- beam tracing
- cone tracing
- image based lighting
- metropolis light transport
- path tracing
- photon mapping
- radiosity
- ray tracing
These algorithms incorporate both diffuse inter-reflection and specular reflection (except for radiosity). Because the calculations involved in GI are more complex than just those used when simulating a direct light source, storing information efficiently becomes an important function.
Wikipedia offers a clear illustration of how global illumination can affect a scene:
“Rendering without global illumination. Areas that lie outside of the ceiling lamp’s direct light lack definition. For example, the lamp’s housing appears completely uniform. Without the ambient light added into the render, it would appear uniformly black.”
“Rendering with global illumination. Light is reflected by surfaces, and colored light transfers from one surface to another. Notice how color from the red wall and green wall (not visible) reflects onto other surfaces in the scene. Also notable is the caustic projected onto the red wall from light passing through the glass sphere.” (http://en.wikipedia.org/wiki/Global_illumination)
{rendering equation}
Computer graphics (CG) uses complex calculations in order to produce images of virtual geometries seen by a camera in a virtual world. In order to produce an image, one must determine the light reaching the camera from a given direction (through a given pixel) based on the optical properties of the surfaces and the lightsources in the virtual world. In order to create realistic digital images, the behavior of light is simulated through an algorithmic equation or the “rendering equation.” Based on physic’s law of the conservation of energy, the rendering equation is an integral equation where “the equilibrium radiance leaving a point is equal to the sum of emitted and reflected radiance under a geometic optics approximation.” Different rendering mechanisms solve this equation through different approaches and have produced a variety of rendering results.
“The rendering equation describes the total amount of light emitted from a point “x” along a particular viewing direction, given a function for incoming light and a BRDF.” (http://en.wikipedia.org/wiki/Rendering_equation)
If radiance is, at some point and direction, then:
outgoing light = emitted light + reflected light, where
reflected light = incoming light from all direction x (surface reflection + cosine of the incident angle)
D3D Book: Lighting, Foundation and Theory (http://wiki.gamedev.net/index.php/D3DBook:%28Lighting%29_Foundation_and_theory)
- mental ray + 3ds max tutorials
to set up render: render set up > common parameters > assign renderer > production > mental ray - if you don’t add any lights, textures will render but be flat - add mr Sun and mr sky mr Sun- simulates direct light from the sun mr Sky- simulates indirect light from sun scattered throughout [...]
- lighting algorithms & effects
{ambient occlusion} A type of rendering that simulates the way light reflects, especially off non-reflective surfaces, which offers better 3d shape and definition. Ambient occlusion works by casting rays in every direction from surface of geometry toward the background or “sky.” The rays that reach the background increase the brightness of the rendering while those [...]
- {mental ray}
Mental Ray Mental ray is a rendering application developed by mental images. The application simulates the behavior of light very accurately to achieve photorealistic results. The program uses utilizes unique sampling and acceleration techniques to provide efficient computer processing on single and multiprocessing machines. Mental Ray uses ray-tracing, a technique of simulating light by tracing [...]
