[Mesa-dev] [PATCH] i965: Use a minimum point width of 1.0.

[Jason Ekstrand]

Do smaller point sizes make sense when multisampling?

On November 17, 2018 03:40:10 Kenneth Graunke <kenneth at whitecape.org> wrote:

> We advertise 1.0 as the minimum point width size, and we probably ought
> to clamp gl_PointSize to the actual range we advertise ([1,255]).  In
> particular, we don't seem to rasterize any points if the shader outputs
> a point size smaller than 1.0, and that seems rather sketchy.
>
> This fixes Piglit's vs-point_size-zero test, which writes 0 for
> gl_PointSize and expects something to be rendered.  However, that test
> may be technically incorrect - according to the OpenGL spec, "If the
> value written to gl_PointSize is less than or equal to zero, results are
> undefined."  Presumably "undefined" includes "don't render any points".
>
> Of course, what the test expects is pretty /reasonable/ behavior, even
> if not mandatory, so we may as well do what it wants...
> ---
> src/mesa/drivers/dri/i965/genX_state_upload.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/mesa/drivers/dri/i965/genX_state_upload.c 
> b/src/mesa/drivers/dri/i965/genX_state_upload.c
> index 5acd0922922..0a0add97d80 100644
> --- a/src/mesa/drivers/dri/i965/genX_state_upload.c
> +++ b/src/mesa/drivers/dri/i965/genX_state_upload.c
> @@ -1547,7 +1547,7 @@ genX(upload_clip_state)(struct brw_context *brw)
>       if (!brw_is_drawing_points(brw) && !brw_is_drawing_lines(brw))
>          clip.ViewportXYClipTestEnable = true;
>
> -      clip.MinimumPointWidth = 0.125;
> +      clip.MinimumPointWidth = 1.0;
>       clip.MaximumPointWidth = 255.875;
>       clip.MaximumVPIndex = viewport_count - 1;
>       if (_mesa_geometric_layers(fb) == 0)
> --
> 2.19.1
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev