diff options
| author | Brian Paul <[email protected]> | 2011-10-04 15:01:05 -0600 |
|---|---|---|
| committer | Brian Paul <[email protected]> | 2011-10-04 15:04:42 -0600 |
| commit | a5f2010735b6af469f57c6c254af9603bb9db18d (patch) | |
| tree | 992590340d7259df0238ee9819662ff9762330e8 | |
| parent | 334a9dd3e60e9c7b8ba7bcceb2c88c2645e6220b (diff) | |
softpipe: fix Z interpolation invariance bug
We want quad/pixel Z values to be interpolated exactly the same for
multi-pass algorithms. Because of how the optimized Z-test code is
written, we can't cull the first quad in a run even if it's totally
killed. See the comment for more info.
NOTE: This is a candidate for the 7.11 branch.
| -rw-r--r-- | src/gallium/drivers/softpipe/sp_quad_fs.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/src/gallium/drivers/softpipe/sp_quad_fs.c b/src/gallium/drivers/softpipe/sp_quad_fs.c index d74d6d4914e..7b08cd0cf30 100644 --- a/src/gallium/drivers/softpipe/sp_quad_fs.c +++ b/src/gallium/drivers/softpipe/sp_quad_fs.c @@ -118,7 +118,16 @@ shade_quads(struct quad_stage *qs, machine->InterpCoefs = quads[0]->coef; for (i = 0; i < nr; i++) { - if (!shade_quad(qs, quads[i])) + /* Only omit this quad from the output list if all the fragments + * are killed _AND_ it's not the first quad in the list. + * The first quad is special in the (optimized) depth-testing code: + * the quads' Z coordinates are step-wise interpolated with respect + * to the first quad in the list. + * For multi-pass algorithms we need to produce exactly the same + * Z values in each pass. If interpolation starts with different quads + * we can get different Z values for the same (x,y). + */ + if (!shade_quad(qs, quads[i]) && i > 0) continue; /* quad totally culled/killed */ if (/*do_coverage*/ 0) |