Anuj Phogat <anuj.phogat at gmail.com> writes:
> Render Target Write message should include source zero alpha value when
> sample-alpha-to-coverage is enabled for an FBO with multiple render targets.
> Source zero alpha value is used as fragment coverage for all the render
> targets.
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> index fefe2c7..7fc28ac 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> @@ -1930,14 +1930,24 @@ fs_visitor::emit_color_write(int target, int index, int first_color_mrf)
> {
> int reg_width = c->dispatch_width / 8;
> fs_inst *inst;
> - fs_reg color = outputs[target];
> + fs_reg color;
> + bool src0_alpha_to_render_target = target > 0 &&
> + c->key.nr_color_regions > 1 &&
> + c->key.sample_alpha_to_coverage;
> +
> + color = (src0_alpha_to_render_target && !index) ?
> + outputs[0] :
> + outputs[target];
> fs_reg mrf;
>
> /* If there's no color data to be written, skip it. */
> if (color.file == BAD_FILE)
> return;
>
> - color.reg_offset += index;
> + if (src0_alpha_to_render_target)
> + color.reg_offset += !index ? 3 : index - 1;
> + else
> + color.reg_offset += index;
Ew, this is really awful.
How about instead..,
> - for (unsigned i = 0; i < this->output_components[target]; i++)
> - emit_color_write(target, i, color_mrf);
> + /* If src0_alpha_to_render_target is true, include source zero alpha
> + * data in RenderTargetWrite message for targets > 0.
> + */
> + output_components = (target && src0_alpha_to_render_target) ?
> + (this->output_components[target] + 1) :
> + this->output_components[target];
>
> - fs_inst *inst = emit(FS_OPCODE_FB_WRITE);
> + for (unsigned i = 0; i < output_components; i++)
> + emit_color_write(target, i, color_mrf);
Replace all of this change with:
if (src0_alpha_to_render_target) {
emit_color_write(0, 3, color_mrf);
color_mrf += reg_width);
}
for (unsigned i = 0; i < this->output_components[target]; i++)
emit_color_write(target, i, color_mrf);
> diff --git a/src/mesa/drivers/dri/i965/brw_wm.c b/src/mesa/drivers/dri/i965/brw_wm.c
> index 5ab0547..210b078 100644
> --- a/src/mesa/drivers/dri/i965/brw_wm.c
> +++ b/src/mesa/drivers/dri/i965/brw_wm.c
> @@ -546,6 +546,8 @@ static void brw_wm_populate_key( struct brw_context *brw,
> /* _NEW_BUFFERS */
> key->nr_color_regions = ctx->DrawBuffer->_NumColorDrawBuffers;
Needs
/* _NEW_MULTISAMPLE */
> + key->sample_alpha_to_coverage = ctx->Multisample.SampleAlphaToCoverage;
and corresponding addition to the state struct below.
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