9.5.2

866 • CHAPTER 18
THE SHADERS • 867
Screen
The gradient is calculated in the space of the screen including Z depth. The object can move through
the gradient, and camera moves will also affect the gradient.
Raster
The gradient is calculated in screen pixels and has no depth information, so no matter how far the
object gets away, the texture is calculated in the same way. The object can move through the gradient,
and camera moves will also affect the gradient.
Cycle disabled (left) and
enabled (right).
Turbulence set to a low
value (left) and a high
value (right).
Octaves set to a low
value (left) and a high
value (right).
Scale set to a low value
(left) and a high value
(right).
Absolute disabled (top)
and enabled (bottom).
Fresnel
This shader calculates the angle (falloff) between surface normals and the viewing angle and uses
this information to attenuate the output. If this angle is 90°, such as at the silhouette of a sphere, the
gradient’s left color will be applied. If, on the other hand, the surface normal points straight at the
camera, the gradient’s right color will be used.