diff options
| author | Brian Paul <[email protected]> | 2008-10-17 09:09:57 -0600 |
|---|---|---|
| committer | Brian Paul <[email protected]> | 2008-10-17 14:14:23 -0600 |
| commit | 81724da4f61f2ba678e2e0376209e1b754e1ecab (patch) | |
| tree | f6f10a5ecbdf16ef452a72a8ddddbb1b389f467f /src | |
| parent | 9fa8671c73fa44a95e2ea7fed6047bddb042796f (diff) | |
cell: use an approximation in compute_lambda_2d() to avoid sqrt
Though, the logf() call still needs attention.
Diffstat (limited to 'src')
| -rw-r--r-- | src/gallium/drivers/cell/spu/spu_texture.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/src/gallium/drivers/cell/spu/spu_texture.c b/src/gallium/drivers/cell/spu/spu_texture.c index 4e12a116cdc..69784c89788 100644 --- a/src/gallium/drivers/cell/spu/spu_texture.c +++ b/src/gallium/drivers/cell/spu/spu_texture.c @@ -414,7 +414,7 @@ sample_texture_2d_bilinear_int(vector float s, vector float t, /** * Compute level of detail factor from texcoords. */ -static float +static INLINE float compute_lambda_2d(uint unit, vector float s, vector float t) { uint baseLevel = 0; @@ -424,11 +424,21 @@ compute_lambda_2d(uint unit, vector float s, vector float t) float dsdy = width * (spu_extract(s, 2) - spu_extract(s, 0)); float dtdx = height * (spu_extract(t, 1) - spu_extract(t, 0)); float dtdy = height * (spu_extract(t, 2) - spu_extract(t, 0)); +#if 0 + /* ideal value */ float x = dsdx * dsdx + dtdx * dtdx; float y = dsdy * dsdy + dtdy * dtdy; float rho = x > y ? x : y; rho = sqrtf(rho); - float lambda = logf(rho) * 1.442695f; +#else + /* approximation */ + dsdx = fabsf(dsdx); + dsdy = fabsf(dsdy); + dtdx = fabsf(dtdx); + dtdy = fabsf(dtdy); + float rho = (dsdx + dsdy + dtdx + dtdy) * 0.5; +#endif + float lambda = logf(rho) * 1.442695f; /* compute logbase2(rho) */ return lambda; } |