[PATCH 1/5] wined3d: Clamp fog coordinate in the vertex shader.

[Matteo Bruni]

Il 08 marzo 2012 22:10, Stefan Dösinger <stefandoesinger at gmx.at> ha scritto:
> Am Donnerstag, 8. März 2012, 18:22:15 schrieb Matteo Bruni:
>> -                shader_addline(buffer, "gl_FogFragCoord = OUT[%u].%c;\n",
>> i, reg_mask[1]);
>> +                shader_addline(buffer, "gl_FogFragCoord =
>> clamp(OUT[%u].%c, 0.0, 1.0);\n", i, reg_mask[1]);
> Is it correct to clamp the fog coord in the vertex shader, or should this be
> done in the pixel shader? The tests do not answer this question because they
> write the same fog coordinate for each vertex.
>
> Imagine for example two lines. In each of those lines, one vertex has oFog =
> 0.0. The other vertex has oFog = 1.1 in one line, and oFog = 100 in the other.
> If the value is clamped per vertex, those lines will look the same. If it's
> clamped per pixel, the latter line will have much steeper gradient
>

I think I wrote a test at some point which shows that it is actually
per-vertex. But I may be mistaken and such a test should be in the
testsuite anyway, so I'll add it.

> Also, what happens to shaders that do not write oFog, but use oPos.z,
> especially in the situations where the near and far clipping planes are
> disabled?

That's another good point, I don't think I tested that (that case
isn't used by either Soul Reaver or the Sands of Time, the two games I
was looking into at the time).
I'll update the patches accordingly.