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1202 Chapter 15: Lights and Cameras
Increasing the Shadow Spread value sof tens shadow edges.
Shadow Bias—The minimum distance from the
point being shaded that an object must be 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 r ays are initially in a very regular
pattern, which can show up in the blurry part
of the shadow as regular ar tifacts. Jittering wil l
convert these artifacts to noise, w hich is generally
less noticeable to the eye. Recommended values
are 0.25 to 1.0. However, very blurry shadows will
requiremorejitter.
Area Shadows Rollout
Create panel > Lights > Create or selec t a light. > General
Parameters rollout > Shadow type > Area Shadows rollout
The Area Shadow generator can be applied to any
light type to achieve t he effect of an area shadow
effect. In order to create an area shadow, the user
needstospecifythedimensionsofavirtuallight
createdto"fake"anareashadow.
Note: When using area l ights, the user should
try to make the propert ies of the light match the
properties in the Area Light Dimensions group of
the Area Shadows rollout.
Tip: Area shadows can take a fair amount of t ime to
render. If you want to create a quick test (or draft)
rendering, you can use the Area/Linear Lights as
Point Lights toggle in t he
Common Parameters
rollout (page 3–27)
of the Render Scene dialog to
speed up your rendering. When this toggle is on,
theshadowsareprocessedasifthelightobjectisa
point source.
Area shadows create a soft edge that becomes mo re
noticeable as the distance between the object and the
shadow increases.
A: Penum bra (soft area)
B: Shadow
Area shadow cast by a point light