[Mesa-dev] [PATCH 1/3] gallium/util: add a helper for calculating primitive count from vertex count

[Ilia Mirkin]

On Fri, Jul 25, 2014 at 9:30 PM, Marek Olšák <maraeo at gmail.com> wrote:
> From: Marek Olšák <marek.olsak at amd.com>
>
> This is needed by the following commit which is a candidate for stable too.
>
> Cc: mesa-stable at lists.freedesktop.org
> ---
>  src/gallium/auxiliary/util/u_prim.h | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/src/gallium/auxiliary/util/u_prim.h b/src/gallium/auxiliary/util/u_prim.h
> index fd95c0b..cf1a18f 100644
> --- a/src/gallium/auxiliary/util/u_prim.h
> +++ b/src/gallium/auxiliary/util/u_prim.h
> @@ -136,6 +136,21 @@ u_prim_vertex_count(unsigned prim)
>     return (likely(prim < PIPE_PRIM_MAX)) ? &prim_table[prim] : NULL;
>  }
>
> +/**
> + * Given a vertex count, return the number of primitives.
> + * For polygons, return the number of triangles.
> + */
> +static INLINE unsigned
> +u_prims_for_vertices(unsigned prim, unsigned num)

This isn't an issue yet, but with PATCH primitives, the number of
vertices per primitive will be variable. (I guess it depends on the
stage you're at...) In my patches, I'm passing the number of patch
vertices via pipe_draw_info -- perhaps it would make sense to just
take that as an argument?

> +{
> +   const struct u_prim_vertex_count *info = u_prim_vertex_count(prim);
> +
> +   if (num < info->min)
> +      return 0;
> +
> +   return 1 + ((num - info->min) / info->incr);
> +}
> +
>  static INLINE boolean u_validate_pipe_prim( unsigned pipe_prim, unsigned nr )
>  {
>     const struct u_prim_vertex_count *count = u_prim_vertex_count(pipe_prim);
> --
> 1.9.1
>
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