wined3d: Correctly display fog for right-handed projection matrix (try 7)

Mon Oct 13 11:05:20 CDT 2014

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Am 2014-10-13 17:14, schrieb Henri Verbeet:
> But the tests still fail to distinguish between taking the absolute
> of ec_pos.z in shader_glsl_generate_ffp_vertex_shader() and taking
> the absolute of gl_FogFragCoord in shader_glsl_generate_fog_code(),
> of course.
Right, how could I miss this.

Joachim, I think a way to test this would be to generate a fog
gradient from -1 to 1 in the fixed function pipeline codepath, set the
Z coordinate to 0 in the projection matrix to prevent clipping and
checking the fog value between the vertices at x=320. If the absolute
value is taken before the interpolation this will result in a fogged
pixel. If it is taken after the interpolation, it will result in an
unfogged pixel.

As a side effect this should also test the clamp(0.0, 1.0) behavior of
the oFog vertex shader output. If the vertex shader side clamp is
correct it'll result in a half fogged middle. We already know vertex
shaders don't do an abs() like the fixed function pipeline, otherwise
both sides of vs=2, tfog=none would be unfogged. If the clamp is
incorrect this would result in fogged on the left, fogged in the
middle, unfogged on the right (and half fogged at x=480).

A third way negative fog coordinates could enter the fog calculation
is a pretransformed vertex with z < 0 combined with table fog. If the
depth test is off clipping is disabled (zenable_test) .