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Old 18-11-2005, 06:49 PM   #1
nemac4
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Join Date: May 2003
Posts: 232
Default simple light trick for fast soft shadows

I was playing with LW lights and had an idea for an alternative to area lights. It may have limited use but seems to work well.

Create a Spotlight with a shadow map at the desired fuzziness, intensity (set it to about half of what you need), and falloff.

Add another Spotlight and parent it to the first light. Set this one to Raytraced Shadows (You can set it to Shadow Mapped if you wish but you should then set fuzz to 0). Now set the intensity to *1.5 over the intensity of the first light. Set the falloff to x/3.2. X being the falloff of the first light.

Turn on Shading Noise Reduction for cleaner shadows or increase the shadow map size. Be sure to turn on Raytrace Shadows.

Here is a render time comparison from my PC.


Scene1: 2 spot lights. 1 Raytraced, 1 Shadow Mapped at 1024 map size and 15 fuzz. 1 point light for fill (no shadows or spec for the fill light). With and without SNR

RT+SM Trick = 6.6 sec | 20.3 sec

Scene2: 1 area light, Quality lvl 4 (I reduced the area light size to match the shadow of the spotlights) and 1 point light for fill (no shadows or spec for the fill light). With and without SNR

Area Light = 25.0 sec | 38.9

Download Scene Files
_________________________________

RT+SM no SNR
Attached Images
File Type: jpg rt_sm_combo_w snr 6.6_sec.jpg (78.7 KB, 165 views)
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