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shadow mapping problems

Started by Marty666 Jan 12, 2004 at 12:38 PM 1 replies 450+ views

Original Post

Jan 12, 2004 at 12:38 PM

Hi all! I''m going to do some realtime shadowmapping in my simple game engine. It''ll be a 3D space shooter. I''d like some dynamic lights (weapons fire, etc) and shadow mapping (sun, maybe explosions) in it. I''ve never done any shadowmapping, so i read through some articles. I''ve got 3 problems to solve: 1: The resolution of the shadowmap should be very high for shadows cast near the camera and far from the light. (Problem when i use it for the sun which is pretty far away

I could split the shadowmap in smaller portions with different resultions (better culling in problem 2 too, but big problem if i have to do ''m all) 2: The shadowmap is only one fustrum big. Should i make more for all directions (fore, back, left, right, up, down)? I could cull away the sides I don''t need. 3: All lights cast infinite shadows this way. Can I fix this by only taking z value''s within the lights range or set the near plane closer? And would a close near plane result in more accurate depth values of the shadowmap? Thanx, Marty

Krohm

346

Krohm

Jan 12, 2004 at 2:15 PM

I also was a big fan of the shadow mapping method but after some experiments with them, I figured out they''re way far from being pratical.

If you could search back the forums maybe you''ll be able to find the original post. The point of it is that updating the shadowmap is usually way too expensive using pbuffers due to context switches. It goes something better with render-to-backbuffer and copy-to-texture but other problems arises.

I suggest you to let shadowmaps alone (at least until uberbuffers are out) and go for shadow volumes instead.

To made the light attenuated, I was planning to use a fragment program to lookup an attenuation table.

Marty666

Author

Marty666

Jan 13, 2004 at 7:52 AM

Ok, since i''m making a 3D space shooter where the shadows only drop from and onto spaceships the geometry won''t be too complex. I figured calculating all the silhouettes would take far too long for like 100 ships (because they''re all visible in space since there is nothing in between them).
I might render the ship to a texture from the lights point of view in b&w. Then project the texture on the other ship. I''d only need to to this if the ships are close enough to cast shadows on eachother (no need for infinite shadows). Maybe i can even find a fast algho to blur the textures edges to create fake soft shadows. Well i''ll leave the softshadows for now and try to do the projected shadow textures.
Anyone thinks this sounds good? Rendering a ship to a b&w texture should be fast enough. Projecting would be slower with complex geometry ships though and has it''s own problems.

Please comment,
Marty

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