2008

Computer Graphics Rendering
The 3D models created in 3ds Max contain geometric data defined in
relationship to a 3D Cartesian coordinate system, referred to as
world space
on page 7976 . The model also contains other information about the material
of each of the objects and the lighting in the scene. The image on a computer
monitor is made up of many illuminated dots, called
pixels on page 7896 . The
task in creating a computer graphics image of a geometric model is to
determine the color for each pixel based on the model information and a
specific viewpoint (camera).
The color of any specific point on a surface in a model is a function of the
physical material properties of that surface and the light that illuminates it.
Two general shading algorithms: local illumination and global illumination are
used to describe how surfaces reflect and transmit light.
Local Illumination
Local illumination algorithms describe only how individual surfaces reflect
or transmit light. Given a description of light arriving at a surface, these
mathematical algorithms, called shaders in 3ds Max, predict the intensity,
color, and distribution of the light leaving that surface. In conjunction with
a material description, different shaders will determine, for example, if a surface
will appear like plastic or metal or if it will appear smooth or rough. 3ds Max
provides a robust interface for defining a wide array of different surface
materials.
After defining how an individual surface interacts with light at the local level,
the next task is to determine where the light arriving at the surface originates.
With the standard
scanline rendering system on page 7918 of 3ds Max, only
the light coming directly from the light sources themselves is considered in
the shading.
For more accurate images, however, it is important to take into account not
only the light sources, but also how all the surfaces and objects in the
environment interact with the light. For example, some surfaces block light,
casting shadows on other surfaces; some surfaces are shiny, in which case we
see in them the reflections of other surfaces; some surfaces are transparent,
in which case we see other surfaces through them; and some surfaces reflect
light onto other surfaces.
Global Illumination
Rendering algorithms that take into account the ways in which light is
transferred between surfaces in the model are called global illumination
5978 | Chapter 18 Rendering