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Missing shadows when light source is inside geometry (using Shadow Maps)
Hi everyone,
I’m experiencing an issue when attempting to have a omni light travel inside some geometry and cast shadows using shadow maps. It seems to be happening at the edges of the geometry and where light is still leaking through the ‘seams’ of the object.
This frame shows the issue on my model of a house & chimney with an omni light approaching the chimney from above –
https://drive.google.com/file/d/1mutXrwd3zE_IjtH0u-39zYqyNAKJhF_8/view?usp=sharingIt occurs with both standard and physical rendering. I’ve checked the model and I’m fairly happy that it’s in good shape i.e. edges joined etc. I’ve tried playing with the normals. I’ve tried giving the model (which was originally single sided) some thickness using both cloth and extrude methods. I’ve increased the shadow map resolution all the way up to 2000×2000 which did improve things somewhat but not enough.
Raytrace shadows work fine but they are too harsh. Area shadows looked too diffuse for what I’m looking for after a cursory play.
I’ve been able to replicate the problem with a simple cube. You can see the sliver of problematic non-shadow in the bottom left edge of the cube which has an omni light inside using a shadow map.
https://drive.google.com/file/d/1jNm4uG0JnTeGtDCeI456FnLVKyZLxVxb/view?usp=sharing
C4D scene: https://drive.google.com/file/d/1fEDW4xloCBpkI5SCV1R5dK3aVu5Vsn3V/view?usp=sharingThis leads me to think it might be an inherent limitation of the shadow map method. Still, I just wanted to check I hadn’t missed something obvious because I’m a relative novice in C4D. Grateful for any ideas.
Thanks in advance 🙂
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2 Replies
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yes, a limitation of the shadow map method which is much quicker than an area light. You can eliminate your sliver by going to the Shadow tab of the light and reducing the Bias but you tend to get objects with self-shadowing artifacts on them. You probably want to use an area light – if you make one with a spherical area shape it’s most like a omni light though you might have to reduce the default size of the spherical area.
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Thank you very much for responding and confirming that quirk of the shadow map.
I’ve used the area shadow set-up you outlined and it’s looking great!
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