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Prune

Exponential shadow maps without NV_depth_buffer_float

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How do I do exponential shadow maps on a card which doesn't support NV_depth_buffer_float (such as GeForce6800)? 32 bit precision appears to be needed for the exponentiated depth values for the algorithm to work.

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I think you can use a float texture with the FBO extension, and write depth values by yourself.

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I assume pre-7xxx hardware can't filter 32 bit floating point texture bilinear or MIP, only nearest? So then custom filter would be required?

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what about encoding the depth as described here:
http://www.gamedev.net/community/forums/topic.asp?topic_id=463075&PageSize=14&WhichPage=2
(first post - float to vec4)

what would happen to the value if you filtered each channel when fetching them?

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I don't see that filtering per channel would give a valid result, since when you add bytes and there's an overflow, for example, it would affect a higher byte.

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Quote:
Original post by Prune
I assume pre-7xxx hardware can't filter 32 bit floating point texture bilinear or MIP, only nearest? So then custom filter would be required?


Sorry, I thought that floating point texture filtering was supported by older cards generations :(. So yes, you would have to write your own custom filter.

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I'll probably try it, but 16-bit would limit the c constant in the exponent to about 10 and make for overly blurry shadows (and maybe other artifacts).

BTW, is it worth it to use MSAA for the shadow map rendering?

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