On Wednesday, July 01, 2015 10:16:28 AM Mike Stroyan wrote: > When there are no color buffer render targets, gen6 and gen7 still > use the first BLEND_STATE element to determine alpha test. > gen6_upload_blend_state was allocating zero elements when > ctx->Color.AlphaEnabled was false. > That left _3DSTATE_CC_STATE_POINTERS or _3DSTATE_BLEND_STATE_POINTERS > pointing to random data from some previous brw_state_batch(). > That sometimes suppressed depth rendering when those bits > happened to mean COMPAREFUNC_NEVER. > This produced flickering shadows for dota2 reborn. > --- > src/mesa/drivers/dri/i965/gen6_cc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/src/mesa/drivers/dri/i965/gen6_cc.c > b/src/mesa/drivers/dri/i965/gen6_cc.c > index 2bfa271..2b76e24 100644 > --- a/src/mesa/drivers/dri/i965/gen6_cc.c > +++ b/src/mesa/drivers/dri/i965/gen6_cc.c > @@ -51,7 +51,7 @@ gen6_upload_blend_state(struct brw_context *brw) > * with render target 0, which will reference BLEND_STATE[0] for > * alpha test enable. > */ > - if (nr_draw_buffers == 0 && ctx->Color.AlphaEnabled) > + if (nr_draw_buffers == 0) > nr_draw_buffers = 1; > > size = sizeof(*blend) * nr_draw_buffers; >
Great catch! Reviewed-by: Kenneth Graunke <kenn...@whitecape.org> And pushed: 9d408a4..fe2b748 master -> master I think we ought to change gen8_blend_state.c as well, but I'm not quite sure what change to make. Either we should make the same change you did here, or delete the whole "We need at least 1 BLEND_STATE written" block. On Gen8+, it looks like the alpha test and other functions that might discard pixels are all in the shared/common DWord, and the per-color target DWord pairs look relatively harmless. I suppose the null RT would still refer to BLEND_STATE[0]...so it might still be worth emitting one. Any thoughts?
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