[Mesa-dev] [PATCH 02/20] t_dd_dmatmp: Allow flat shaded polygons with tri fans

[Ian Romanick]

On 03/23/2015 05:47 AM, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> We can allow rendering flat shaded polygons using tri fans if we check
> the provoking vertex convention.

This sounds reasonable since it matches the DX behavior.  Is there a
piglit test that would hit this?

> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  src/mesa/tnl_dd/t_dd_dmatmp.h | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/src/mesa/tnl_dd/t_dd_dmatmp.h b/src/mesa/tnl_dd/t_dd_dmatmp.h
> index 5ea2d31..3ed4a98 100644
> --- a/src/mesa/tnl_dd/t_dd_dmatmp.h
> +++ b/src/mesa/tnl_dd/t_dd_dmatmp.h
> @@ -406,7 +406,9 @@ static void TAG(render_poly_verts)( struct gl_context *ctx,
>  
>        FLUSH();
>     }
> -   else if (HAVE_TRI_FANS && ctx->Light.ShadeModel == GL_SMOOTH) {
> +   else if (HAVE_TRI_FANS &&
> +	    (ctx->Light.ShadeModel == GL_SMOOTH ||
> +	     ctx->Light.ProvokingVertex == GL_FIRST_VERTEX_CONVENTION_EXT)) {
>        TAG(render_tri_fan_verts)( ctx, start, count, flags );
>     } else {
>        fprintf(stderr, "%s - cannot draw primitive\n", __FUNCTION__);
> @@ -885,7 +887,9 @@ static void TAG(render_poly_elts)( struct gl_context *ctx,
>  	 FLUSH();
>  	 currentsz = dmasz;
>        }
> -   } else if (HAVE_TRI_FANS && ctx->Light.ShadeModel == GL_SMOOTH) {
> +   } else if (HAVE_TRI_FANS &&
> +	      (ctx->Light.ShadeModel == GL_SMOOTH ||
> +	       ctx->Light.ProvokingVertex == GL_FIRST_VERTEX_CONVENTION_EXT)) {
>        TAG(render_tri_fan_verts)( ctx, start, count, flags );
>     } else {
>        fprintf(stderr, "%s - cannot draw primitive\n", __FUNCTION__);
> @@ -1109,7 +1113,9 @@ static GLboolean TAG(validate_render)( struct gl_context *ctx,
>  	    ok = GL_TRUE;
>  	 }
>  	 else {
> -	    ok = (HAVE_TRI_FANS && ctx->Light.ShadeModel == GL_SMOOTH);
> +	    ok = (HAVE_TRI_FANS &&
> +		  (ctx->Light.ShadeModel == GL_SMOOTH ||
> +		   ctx->Light.ProvokingVertex == GL_FIRST_VERTEX_CONVENTION_EXT));
>           }
>  	 break;
>        case GL_QUAD_STRIP:
>