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Fix rendering of mars globe in main menu with some drivers

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The problem was that negative values (from dhewm3tmpres.xyz) were passed
to POW, and POW doesn't have to support negative bases, according to
ARB_fragment_program.txt, and Intels Linux drive apparently doesn't,
see also https://gitlab.freedesktop.org/mesa/mesa/-/issues/5131

Using MUL_SAT instead of MUL to clamp the value that gets passed to POW
afterwards to [0, 1] fixes the problem without any disadvantages.
This commit is contained in:
Daniel Gibson 2021-08-17 19:43:01 +02:00
parent 981863788f
commit 78eef43d50
1 changed files with 5 additions and 1 deletions
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6
neo/renderer/draw_arb2.cpp
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@ -464,7 +464,11 @@ void R_LoadARBProgram( int progIndex ) {
// outColor.a = dhewm3tmpres.a;
const char* extraLines =
"# gamma correction in shader, injected by dhewm3 \n"
"MUL dhewm3tmpres.xyz, program.env[4], dhewm3tmpres;\n" // first multiply with brightness
// MUL_SAT clamps the result to [0, 1] - it must not be negative because
// POW might not work with a negative base (it looks wrong with intel's Linux driver)
// and clamping values >1 to 1 is ok because when writing to result.color
// it's clamped anyway and pow(base, exp) is always >= 1 for base >= 1
"MUL_SAT dhewm3tmpres.xyz, program.env[4], dhewm3tmpres;\n" // first multiply with brightness
"POW result.color.x, dhewm3tmpres.x, program.env[4].w;\n" // then do pow(dhewm3tmpres.xyz, vec3(1/gamma))
"POW result.color.y, dhewm3tmpres.y, program.env[4].w;\n" // (apparently POW only supports scalars, not whole vectors)
"POW result.color.z, dhewm3tmpres.z, program.env[4].w;\n"