Ideally we should fix this in libtxc_dxtn, but there is no central repository for that library, no versioning, and no official releases, and I am pretty sure that nobody would update that lib just to get this fix. Putting this fix in Mesa ensures that it will find its way to users, which is important. Marek <div class="gmail_quote">On Wed, Feb 16, 2011 at 4:18 AM, Marek Olšák <<a href="mailto:maraeo@gmail.com">maraeo@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"> This is a workaround for a bug in libtxc_dxtn. Fixes: - piglit/GL_EXT_texture_compression_s3tc/fbo-generatemipmap-formats --- src/gallium/auxiliary/util/u_format_s3tc.c | 16 ++++++++++++++-- 1 files changed, 14 insertions(+), 2 deletions(-) diff --git a/src/gallium/auxiliary/util/u_format_s3tc.c b/src/gallium/auxiliary/util/u_format_s3tc.c index bb989c2..31288e3 100644 --- a/src/gallium/auxiliary/util/u_format_s3tc.c +++ b/src/gallium/auxiliary/util/u_format_s3tc.c @@ -416,8 +416,20 @@ util_format_dxt1_rgba_pack_rgba_8unorm(uint8_t *dst_row, unsigned dst_stride, uint8_t tmp[4][4][4]; /* [bh][bw][comps] */ for(j = 0; j < bh; ++j) { for(i = 0; i < bw; ++i) { - for(k = 0; k < comps; ++k) { - tmp[j][i][k] = src[(y + j)*src_stride/sizeof(*src) + (x + i)*comps + k]; + const uint8_t *srcp = &src[(y + j)*src_stride/sizeof(*src) + (x + i)*comps]; + /* Workaround for a bug in libtxc_dxtn. + * If the color is (0,0,0,0), it is compressed as (0,0,0,1), + * which is incorrect. Any other (x,y,z,0) color is compressed + * correctly as (0,0,0,0), so let's use (1,0,0,0). */ + if (srcp[0] == 0 && srcp[1] == 0 && srcp[2] == 0 && srcp[3] == 0) { + tmp[j][i][0] = 255; + tmp[j][i][1] = 0; + tmp[j][i][2] = 0; + tmp[j][i][3] = 0; + } else { + for(k = 0; k < comps; ++k) { + tmp[j][i][k] = srcp[k]; + } } } } -- 1.7.1 </blockquote></div>