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Projective texture shadows

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Hi, I want to be able to some kind of projective texture shadow technique on pre-shader hardware. The idea I have in mind is to render all of my occlusion meshes into a render-texture and then project that render-texture onto my scene to kind of fake shadowmapping. Its only intended to give an approximation of shadows - doesn't need to be accurate and the light source will pretty much be from above so I don't need to worry too much about shadows being on faces that they shouldn't be etc.. Is this just a crazy idea?

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Well, i your scene is coloured other than black or grey then the shadow will be coloured. This means you will ahve to do some more processing to get it black. Shadow maps are dead easy to implement. I recommend that.

Dave

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Sounds like planar shadowing. That technique only really works for a plane, but if you limit yourself to a light from directly above, you should be able to work it out alright with non-planar terrain, I think.

I'm not too sure how you'd do that without shaders though (well, maybe with a slowish render-to-texture) :(

Hope this helps.

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Sounds like plain old lightmaps to me, is there something I dont get?, in short, just render the shadows and light colors in plain "white" textures during preprocessing, then use multitexturing to blend both the texture and the lightmap, you can even use radiosity on your lightmap generation algorithm.

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Okay, perhaps I didn't explain that correctly.. :)

The scene is static but the occlusion meshes will be moving around (flying in this case). I need a shadow solution for pre-shader hardware. I would just use the old Nintendo 'black' blob approach but since its not a totally planar ground (i.e there are buildings and rocks etc) the blob approach falls over. However, if I were to project this blob texture onto the static scene (ignoring the texel distance check that shadowmapping gives you) then I can approximate something near shadowmapping - just not as accurate or even pretty.

Now, if I could do that with one blob can I render all the blobs to a render-target and project that texture onto the static scene?

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