[Mesa-dev] [PATCH 1/2] st/mesa: adjust blending modes if we don't have destination alpha
Brian Paul
brianp at vmware.com
Tue Apr 28 16:52:10 PDT 2015
On 04/28/2015 04:35 PM, Ilia Mirkin wrote:
> On Tue, Apr 28, 2015 at 6:26 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>> Reviewed-by: Ilia Mirkin <imirkin at alum.mit.edu>
>
> aaaactually....
>
>>
>> Awesome! Now I can go remove this set of hacks from freedreno. And
>> this fixes the same issue in nouveau. Thanks for doing it the real way
>> :)
>>
>> On Tue, Apr 28, 2015 at 6:16 PM, Brian Paul <brianp at vmware.com> wrote:
>>> If the user requested a GL_RGB texture but the driver actually allocated
>>> an RGBA texture, the alpha values in the texture may not be defined.
>>>
>>> If we later bind the texture as a color target and try to blend into
>>> it with GL_DST_ALPHA or GL_ONE_MINUS_DST_ALPHA we may blend with
>>> undefined alpha values when, in fact, the dest alpha value should be one.
>>> So replace GL_DST_ALPHA/GL_ONE_MINUS_DST_ALPHA with GL_ONE/GL_ZERO.
>>>
>>> Fixes the piglit fbo-blending-formats test for some GL_RGB formats
>>> with the VMware driver. Also tested with llvmpipe.
>>> ---
>>> src/mesa/state_tracker/st_atom_blend.c | 38 +++++++++++++++++++++++++---------
>>> 1 file changed, 28 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/src/mesa/state_tracker/st_atom_blend.c b/src/mesa/state_tracker/st_atom_blend.c
>>> index 6bb4077..30bff7a 100644
>>> --- a/src/mesa/state_tracker/st_atom_blend.c
>>> +++ b/src/mesa/state_tracker/st_atom_blend.c
>>> @@ -44,10 +44,21 @@
>>> /**
>>> * Convert GLenum blend tokens to pipe tokens.
>>> * Both blend factors and blend funcs are accepted.
>>> + * \param destBaseFormat the base format of the render target, such as
>>> + * GL_RGBA, GL_RGB, GL_RED, GL_ALPHA, etc.
>>> */
>>> static GLuint
>>> -translate_blend(GLenum blend)
>>> +translate_blend(GLenum blend, GLenum destBaseFormat)
>>> {
>>> + /* If we don't have destination alpha and the blend factor is either
>>> + * GL_DST_ALPHA or GL_ONE_MINUS_DST_ALPHA then we use
>>> + * PIPE_BLENDFACTOR_ONE or _ZERO instead.
>>> + */
>>> + const bool haveDstA = (destBaseFormat == GL_RGBA ||
>>> + destBaseFormat == GL_ALPHA ||
>>> + destBaseFormat == GL_INTENSITY ||
>>> + destBaseFormat == GL_LUMINANCE_ALPHA);
>>> +
>>> switch (blend) {
>>> /* blend functions */
>>> case GL_FUNC_ADD:
>>> @@ -69,7 +80,7 @@ translate_blend(GLenum blend)
>>> case GL_SRC_ALPHA:
>>> return PIPE_BLENDFACTOR_SRC_ALPHA;
>>> case GL_DST_ALPHA:
>>> - return PIPE_BLENDFACTOR_DST_ALPHA;
>>> + return haveDstA ? PIPE_BLENDFACTOR_DST_ALPHA : PIPE_BLENDFACTOR_ONE;
>>> case GL_DST_COLOR:
>>> return PIPE_BLENDFACTOR_DST_COLOR;
>>> case GL_SRC_ALPHA_SATURATE:
>>> @@ -91,7 +102,7 @@ translate_blend(GLenum blend)
>>> case GL_ONE_MINUS_DST_COLOR:
>>> return PIPE_BLENDFACTOR_INV_DST_COLOR;
>>> case GL_ONE_MINUS_DST_ALPHA:
>>> - return PIPE_BLENDFACTOR_INV_DST_ALPHA;
>>> + return haveDstA ? PIPE_BLENDFACTOR_INV_DST_ALPHA : PIPE_BLENDFACTOR_ZERO;
>>> case GL_ONE_MINUS_CONSTANT_COLOR:
>>> return PIPE_BLENDFACTOR_INV_CONST_COLOR;
>>> case GL_ONE_MINUS_CONSTANT_ALPHA:
>>> @@ -208,14 +219,21 @@ update_blend( struct st_context *st )
>>> else if (ctx->Color.BlendEnabled) {
>>> /* blending enabled */
>>> for (i = 0, j = 0; i < num_state; i++) {
>>> + const struct gl_renderbuffer *rb;
>>> + GLenum baseFormat;
>>>
>>> blend->rt[i].blend_enable = (ctx->Color.BlendEnabled >> i) & 0x1;
>>>
>>> if (ctx->Extensions.ARB_draw_buffers_blend)
>>> j = i;
>>>
>>> + /* _NEW_BUFFERS */
>>> + /* Get the base format of the render target */
>>> + rb = ctx->DrawBuffer->_ColorDrawBuffers[j];
>
> That's the wrong render target, no? You need the i'th render target.
Ah, I think you're right.
BTW, I think there's more i/j mix-ups in this code (independent of this
patch). I'll send a separate patch for that after I check the specs.
> And what happens if I'm not using independent blend but one of the
> RT's is RGB while the other is RGBA?
Yeah, there's no simple fix for that, AFAIK.
>
> -ilia
>
>>> + baseFormat = rb ? rb->_BaseFormat : GL_RGBA;
>>> +
>>> blend->rt[i].rgb_func =
>>> - translate_blend(ctx->Color.Blend[j].EquationRGB);
>>> + translate_blend(ctx->Color.Blend[j].EquationRGB, baseFormat);
>>>
>>> if (ctx->Color.Blend[i].EquationRGB == GL_MIN ||
>>> ctx->Color.Blend[i].EquationRGB == GL_MAX) {
>>> @@ -225,13 +243,13 @@ update_blend( struct st_context *st )
>>> }
>>> else {
>>> blend->rt[i].rgb_src_factor =
>>> - translate_blend(ctx->Color.Blend[j].SrcRGB);
>>> + translate_blend(ctx->Color.Blend[j].SrcRGB, baseFormat);
>>> blend->rt[i].rgb_dst_factor =
>>> - translate_blend(ctx->Color.Blend[j].DstRGB);
>>> + translate_blend(ctx->Color.Blend[j].DstRGB, baseFormat);
>>> }
>>>
>>> blend->rt[i].alpha_func =
>>> - translate_blend(ctx->Color.Blend[j].EquationA);
>>> + translate_blend(ctx->Color.Blend[j].EquationA, baseFormat);
>>>
>>> if (ctx->Color.Blend[i].EquationA == GL_MIN ||
>>> ctx->Color.Blend[i].EquationA == GL_MAX) {
>>> @@ -241,9 +259,9 @@ update_blend( struct st_context *st )
>>> }
>>> else {
>>> blend->rt[i].alpha_src_factor =
>>> - translate_blend(ctx->Color.Blend[j].SrcA);
>>> + translate_blend(ctx->Color.Blend[j].SrcA, baseFormat);
>>> blend->rt[i].alpha_dst_factor =
>>> - translate_blend(ctx->Color.Blend[j].DstA);
>>> + translate_blend(ctx->Color.Blend[j].DstA, baseFormat);
>>> }
>>> }
>>> }
>>> @@ -285,7 +303,7 @@ update_blend( struct st_context *st )
>>> const struct st_tracked_state st_update_blend = {
>>> "st_update_blend", /* name */
>>> { /* dirty */
>>> - (_NEW_COLOR | _NEW_MULTISAMPLE), /* XXX _NEW_BLEND someday? */ /* mesa */
>>> + (_NEW_BUFFERS | _NEW_COLOR | _NEW_MULTISAMPLE), /* mesa */
>>> 0, /* st */
>>> },
>>> update_blend, /* update */
>>> --
>>> 1.9.1
>>>
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