[Mesa-dev] [PATCH] u_gen_mipmap: Use untampered cubemap texture coords when generating mipmaps.
brianp at vmware.com
Tue Nov 19 11:44:46 PST 2013
On 11/19/2013 11:54 AM, jfonseca at vmware.com wrote:
> From: José Fonseca <jfonseca at vmware.com>
> It's not necessary to scale down cubemap texture coords when generating
> mipmaps: we are doing a 2x minification therefore it's guaranteed that
> the texture coords will always be at least 1 texel away of the edges.
> Scaling down can actually be harmful, as it may cause artefacts when
> generating mipmaps with nearest filtering. Sample points will lie
> exactly in the middle each 2x2 texels, so the scaling factor was causing
> different texels to be take on each quadrant of the cube face. This is
> apparent with a 1x1 checkerboard pattern in the base mipmap level:
> instead of next mipmap level receiving a constant color throughout the
> face, it will have different colors for each quadrant of the face.
> The behaviour for blits is left untouched for now, but the cubemap
> texture coord scaling hack should be reconsidered eventually.
> src/gallium/auxiliary/util/u_blit.c | 3 ++-
> src/gallium/auxiliary/util/u_blitter.c | 3 ++-
> src/gallium/auxiliary/util/u_gen_mipmap.c | 3 ++-
> src/gallium/auxiliary/util/u_texture.c | 11 +++++++++--
> src/gallium/auxiliary/util/u_texture.h | 5 ++++-
> 5 files changed, 19 insertions(+), 6 deletions(-)
Reviewed-by: Brian Paul <brianp at vmware.com>
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