Dual-Paraboloïd Maps

[Zaknafein]

I heard about those a long time ago, before cubemaps became common use and the "default choice" for image-based lighting or reflections...
But it looks like dual-paraboloid maps are a very good choice when you can't discard cubemap faces, when you actually need to render the whole 360 degree span. Two textures, two render state changes, two rendersurfaces!

It implies some math to get the reflected vectors (not as simple as a texCUBE intrisic) but still, a very interesting path to explore, methinks.

http://graphicsrunner.blogspot.com/2008/07/dual-paraboloid-reflections.html
http://graphicsrunner.blogspot.com/2008/07/dual-paraboloid-variance-shadow-mapping.html

[WEst]

Yep, I heard of them some time ago too, when I did some research about omni lights. They are great but afaik they have problems if the scene hasn't enough polys.

Has anyone already implemented them in TV3D? It would be great to have some comparison with standard cubemapped omnilight shadows, as these should be a larg amount faster.

[Mietze]

sounds like someone is active on ziggyware ...

[Zaknafein]

Haha, that makes two of us then.
I'm not actually active on the forums or anything, but I do like to read what he posts. Usually very interesting stuff.

[Mietze]

Ya, and its also some useful information for XNA stuff... and probably fez

[jviper]

I was able to use the shader fx file in TV3D. It is a bitr faster since it's only a thrid the rendering, but that's about it.

[BlindSide]

They've sort of faded out with the advent of cubemaps, due to the high level of tessellation required for interpolation. That was about the biggest drawback. Still worth looking at though I would imagine, especially as poly counts per-mesh are on the rise.

While I'm still a fan of the cubemap, I would suggest using dual-paraboloid as a lower-quality setting for shadowmaps to get a nice speedup, or perhaps use them for distant objects (a sort of LOD for pointlights, especially useful for outdoors I would think).

[BlindSide]

Oh and they're pretty decent for reflection/refraction - with a complex model like a character, the interpolation errors are fairly well hidden unless the object is the center of attention.