[Bug 66067] Trine 2's fragment normal buffer is mixtextured on Radeon HD 6770 (Juniper)

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Tue Sep 17 18:37:14 PDT 2013


https://bugs.freedesktop.org/show_bug.cgi?id=66067

--- Comment #10 from Nicholas Miell <nmiell at gmail.com> ---
To quote the Cg tutorial:

"Notice that the code for the shadow map query is virtually identical to the
code for the projective texture lookup in Example 9-6. To a Cg programmer,
shadow maps are like other projective textures, except that instead of
returning a texture color,tex2Dproj returns a value representing shadow
coverage. The underlying hardware implementation automatically recognizes when
a texture is a depth texture (instead of a color texture) and performs the
shadow map comparison instead of an ordinary texture fetch."

I suspect that the Cg compiler always compiles tex2Dproj to a TEX instruction
with the SHADOW2D target and relies on OpenGL implementations always
transparently using normal sampling on non-depth non-stencil textures.

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