swrast: anisotropic filtering extension

Anisotropic filtering extension for swrast intended to be used by osmesa
to create high quality renderings.
Based on Higher Quality Elliptical Weighted Avarage Filter (EWA).
A 2nd implementation using footprint assembly is also provided.

Signed-off-by: Brian Paul <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mesa/swrast/s_span.c b/src/mesa/swrast/s_span.c
index f0524e0610e..f81de3c0c7b 100644
--- a/src/mesa/swrast/s_span.c
+++ b/src/mesa/swrast/s_span.c
@@ -492,6 +492,13 @@ interpolate_texcoords(struct gl_context *ctx, SWspan *span)
             const struct gl_texture_image *img = obj->Image[0][obj->BaseLevel];
             needLambda = (obj->Sampler.MinFilter != obj->Sampler.MagFilter)
                || ctx->FragmentProgram._Current;
+            /* LOD is calculated directly in the ansiotropic filter, we can
+             * skip the normal lambda function as the result is ignored.
+             */
+            if (obj->Sampler.MaxAnisotropy > 1.0 &&
+                obj->Sampler.MinFilter == GL_LINEAR_MIPMAP_LINEAR) {
+               needLambda = GL_FALSE;
+            }
             texW = img->WidthScale;
             texH = img->HeightScale;
          }