Datasheet

32 Chapter 1: Texturing and Lighting a Product, Part 1
The final color of each pixel within a scanline is based on the material qualities of the •
polygon face found within the pixel. In addition, the surface’s relationship to lights
and cast shadows is taken into account.
To optimize memory usage, the scanline approach is often broken into tiles. The size of •
any given tile is based on the number and complexity of surfaces found with a particu-
lar area of the camera’s view. For example, when you render with Maya Software in the
Render View window, the bottom-center section of the view is the first to appear.
In contrast, the raytracing process fires off a virtual ray from the camera eye through each
pixel of the view plane. Essentially, the view plane is a 2D grid that’s perpendicular to the
axis of the camera lens (that is, the grid is coplanar to the virtual film back). The grid pos-
sesses the same dimensions as the pixel size of the chosen render resolution. The first surface
a ray hits determines the pixel color. That is, the material qualities of the surface are used in
the shading calculation of the pixel. If the surface is reflective or refractive, additional rays
are created at the surface intersection point. One ray represents the reflection, and one ray
represents the refraction. These rays continue until they intersect another surface. Additional
reflection and/or refraction rays are born at the new intersection point if the associated mate-
rial is reflective or refractive. To prevent an infinite number of rays from being born, limits
are placed on the total number of permitted rays. Refraction differs from reflection in that a
refractive ray travels through a surface. Real-world refractive materials, such as glass or water,
are perceived as transparent or semitransparent.
With Maya Software, raytracing is activated via the Raytracing check box
found within the Raytracing Quality section of the Maya Software tab of the
Render Settings window (see Figure 1.38). The number of times an initial ray is
allowed to reflect or refract is controlled by the Reflections and Refractions attri-
butes. For example, if Reflections is set to 3, a ray is allowed to create three addi-
tional reflection rays. Along those lines, any reflective surface is allowed to reflect
any ray that hits it so long as that ray has been previously reflected two times or
less. Additionally, you can control the number of raytraced shadows that
appear in recursive reflections or retractions by setting the Shadows attri-
bute. If Shadows is set to 2, the render creates one recursive raytraced shadow
in any reflection or refraction. If Shadows is set to 1.0, standard shadows
appear but no raytraced shadows appear within reflections or refractions. In
contrast, depth map shadows appear in all reflections and refractions and
are unaffected by the Shadows attribute. For more information on raytraced
shadows, see Chapter 2.
Blinn, Phong, Phong E, and Anisotropic materials possess a Raytrace
Options section (see Figure 1.39).
Figure 1.38
The Raytracing Quality section of
the Maya Software tab in the Render
Settings window
Figure 1.39
The Raytrace Options section of a Blinn
material
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