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1360 Chapter 15: Lights and Cameras
Increase Shadow Quality to fix banding in the
penumbra, and eliminate the noise pattern from
jittering.
Increasing the Shadow Quality value produces a more accurate
penumbra (soft area) within the contour defined by the
Shadow Integrity value.
Sample Spread—The radius, in pixels, to blur the
antialiased edge.
Note: As this value increases, so does the quality
of the blur. However, increasing this value also
increases the likelihood of missing smal l objects.
To avoid this problem, increase the value of
Shadow Integrity.
Shadow B ias—The minimum distance that an
object must be from the point being shaded in
order to cast a shadow. This prevents blurred
shadows from affecting surfaces they shouldn’t.
Note: As you increase the blur value, you should
also increase the bias.
Jitter Amount—Adds randomness to the ray
positions. The rays are initially in a very regular
pattern, which can show up in the blurry part
of the shadow as regular ar tifacts. Jittering will
convert these artifacts to noise, which is generally
less noticeable to the eye. Recommended values
are 0.25 to 1.0. However, very blurry shadows
requiremorejitter.
Increasing jitter blends the individual shadow samples.
Area Light Dimen sions group
The software uses these dimensions to compute
the area shadow ing . They do not affect the actual
light object.
Lengt h—Sets the length of the area shadow.
Width—Sets the width of the area shadow.
Height—Sets the height of the area shadow.
mental r ay S hadow M ap R ollout
Create panel > Lights > Create a light. > General
Parameters rollout > Select “mental ray Shadow Map
shadows.” > mental ray Shadow Map rollout
Choosing “mental ray Shadow Map” as the
shadow type tells the mental ray renderer (page
3–78) to generate shadows using the mental ray
shadow-map algorithm. If you render with the
default scanline renderer (page 3–38) instead, no
shadows appear in the rendering.