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View Full Version : Spot lights shine right thru solid objects



Johnny
12-10-2005, 01:30 PM
I have a spot lite with shadowmap shadows which, when placed overhead of objects shines thru part of those objects, even tho they have no holes in them, and even after I made their polys 2-sided.

Is there some reason for this behavior?

thanks!

J

toby
12-10-2005, 09:21 PM
Don't worry about it if it''s only in the viewport, but if it's in the render, try increasing the shadow map size or decreasing the shadow map angle.

Johnny
12-10-2005, 09:23 PM
Don't worry about it if it''s only in the viewport, but if it's in the render, try increasing the shadow map size or decreasing the shadow map angle.


OK..will do.. been a long day of experiments and rendering. I'll try this tomorrow.

thanks for all the suggestions and words; it's been a BIG help in this!

J

toby
12-10-2005, 10:07 PM
Glad I could help!

Think of Shadow maps as if they were a bitmap being projected from the light, and the shadow map size is the resolution of the bitmap ( 512 would mean 512x512 ) and the shadow map angle is how much the map is spread out or concentrated. If the map size is too small, and/or the shadow map angle is spread out too far, you'll start to see big pixels in the shadows. If the map size is too big, it will take longer to render than raytracing would.

To optimize the maps, turn off 'Fit spotlight cone' in the shadow tab of Light properties, look through the light, and decrease the angle until it just surrounds the object that needs a shadow.

Shadow mapped lights have been the standard because raytracing was so impractical for a long time and gave sharp-edge shadows. It's still the standard in many places, they're still used, instead of raytracing, in most Renderman pipelines including Pixar films, and also the Star Wars movies. You can tell because the shadows are the same darkness from beginning to end, and also have that 'floating' look you've mentioned.