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GPU: Add atan_fast

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This commit is contained in:
Clément Foucault
2024-05-09 12:33:13 +02:00
parent 94a83bcf04
commit 732d0c56df
1 changed files with 19 additions and 0 deletions
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19
source/blender/gpu/shaders/common/gpu_shader_math_fast_lib.glsl
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@@ -32,4 +32,23 @@ vec2 acos_fast(vec2 v)
return v;
}
float atan_fast(float x)
{
float a = abs(x);
float k = a > 1.0 ? (1.0 / a) : a;
float s = 1.0 - (1.0 - k); /* Crush denormals. */
float t = s * s;
/* http://mathforum.org/library/drmath/view/62672.html
* Examined 4278190080 values of atan:
* 2.36864877 avg ULP diff, 302 max ULP, 6.55651e-06 max error // (with denormals)
* Examined 4278190080 values of atan:
* 171160502 avg ULP diff, 855638016 max ULP, 6.55651e-06 max error // (crush denormals)
*/
float r = s * fma(0.43157974, t, 1.0) / fma(fma(0.05831938, t, 0.76443945), t, 1.0);
if (a > 1.0) {
r = 1.57079632679489661923 - r;
}
return (x < 0.0) ? -r : r;
}
#endif /* GPU_SHADER_MATH_FAST_LIB_GLSL */