[Mesa-dev] [PATCH 1/2] gallium/u_blitter: enable MSAA when blitting to MSAA surfaces

[Marek Olšák]

On Thu, Dec 7, 2017 at 5:09 PM, Brian Paul <brianp at vmware.com> wrote:
> If we're doing a Z -> Z MSAA blit (for example) we need to enable
> msaa rasterization when drawing the quads so that we can properly
> write the per-sample values.
>
> This fixes a number of Piglit ext_framebuffer_multisample blit tests
> such as ext_framebuffer_multisample/no-color 2 depth combined with
> the VMware driver.
>
> ---
>
> Marek, I'm not sure how this could have worked without MSAA enabled.
> Perhaps you can comment.

Enabling MSAA rasterization should have no effect, because the blitter
draws an axis-aligned quad, so each pixel will generate only one
sample.

radeon drivers still obey the sample mask even if MSAA is disabled. I
guess svga doesn't.

I guess enabling MSAA is OK, but now we also have to save and restore
the "min_samples" value if it's not 1, because we don't want to use
sample shading because u_blitter doesn't need it.

Marek