Re: [Mesa3d-dev] shadow extensions

[Stephen J B. <sj...@li...>]

On Wed, 21 Feb 2001, 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.
 
It's not a universal panacea though.

The most serious problem is that the resolution with which the polygon
is rendered from the perspective of the light source generally
differs radically from the resolution it'll appear to be from
the perspective of the viewer.  Hence, you can get shadows
plastered inappropriately on the wrong surfaces - or the shadows
may have VERY pixellated or have severe aliasing artifacts.

But - having said that - in the right situations it works
amazingly well. It's a clever hack.  You just have to know when
you can and can't use it.

----
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