Re: [Mesa3d-dev] shadow extensions

[Brian P. <br...@va...>]

Gareth Hughes wrote:
> 
> Brian Paul wrote:
> >
> > While working on the texture image code I had to fix some
> > things related to color index (paletted) texture images.  That
> > got me thinking about other texture formats like depth textures.
> > So, I implemented the GL_SGIX_depth_texture extension and then
> > GL_SGIX_shadow to exercise it.  GL_SGIX_shadow_ambient was a
> > simple addition on top of that.
> >
> > ...
> >
> > My implementation isn't 100% complete either.  Right now, the
> > depth texture is only sampled with nearest/nearest filtering
> > and the texels are always stored as floats.  I'll try to fix
> > those things in the not-too distant future.
> 
> Great work!  I remember talking about this with you at SIGGRAPH last
> year -- I'm really interested in checking this out.

The code was surprisingly simple after I got the new teximage stuff
sorted out.

I want to experiment with shadow map sampling.  Linear filtering
won't necessarily give better results than nearest filtering.
Consider the discontinuities along object profiles.  I might try
taking 4 depth samples, perform 4 R comparisons then use the
results of those 4 tests to determine if the fragment is shadowed
or not.  I'm also curious how mipmapping will work out.

-Brian