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Simple Shadows

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I understand the principal behind creating primitive shadows onto a flat surface. A trivial case of projecting the model (whatever that might be), from the light source to the flat surface (in my case, really simple, the plane the shadow will be cast on is on the horizontal at y=0). So, knowing the principal, you''d think it''d be easy to implement, but I''m completely confused. Can anyone help?

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Could always do it realistically, and easily. They talk about this effect in the red book. Basically you take screenshots of your image with each individual light activated. Then you blend the images in the accumulation buffer and you''re done. These are called soft shadows. Only problem is that they are slow

"Free advice is seldom cheap."
-- Rule of Acquisition #59

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@RipTorn: Scaling the model to 1,0,1 would generate a totaly flat model. Drawing this model on the groung at 0,0,0 would generate a good shadow under the 1,1,1 model. Is this what you do?

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RipTorn: what you do is correct, but for directional light that comes from the Y axis only. Though that shows the technique.

Mark J. Kilgard wrote something about planar shadows and I found it again at opengl.org at this page. Also he wrote something about volumetric stencil shadows (at opengl.org too) at this page. Check them out !

[edited by - vincoof on December 4, 2002 6:21:00 AM]

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vincoof, you''re a star!
Thankyou for all your answers; I should be sorted now.


Neil.

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