[Mesa-dev] [PATCH] draw: get rid of special logic to not emit null tris

[Brian Paul]

On 05/17/2018 10:30 AM, sroland at vmware.com wrote:
> From: Roland Scheidegger <sroland at vmware.com>
> 
> I've confirmed after 77554d220d6d74b4d913dc37ea3a874e9dc550e4 we no
> longer need this to pass some tests from another api (as we no longer
> generate the bogus extra null tris in the first place).
> ---
>   src/gallium/auxiliary/draw/draw_pipe_clip.c | 38 -----------------------------
>   1 file changed, 38 deletions(-)
> 
> diff --git a/src/gallium/auxiliary/draw/draw_pipe_clip.c b/src/gallium/auxiliary/draw/draw_pipe_clip.c
> index 46118b6..2a9c944 100644
> --- a/src/gallium/auxiliary/draw/draw_pipe_clip.c
> +++ b/src/gallium/auxiliary/draw/draw_pipe_clip.c
> @@ -210,30 +210,6 @@ static void interp(const struct clip_stage *clip,
>   }
>   
>   /**
> - * Checks whether the specified triangle is empty and if it is returns
> - * true, otherwise returns false.
> - * Triangle is considered null/empty if its area is equal to zero.
> - */
> -static inline boolean
> -is_tri_null(const struct clip_stage *clip, const struct prim_header *header)
> -{
> -   const unsigned pos_attr = clip->pos_attr;
> -   float x1 = header->v[1]->data[pos_attr][0] - header->v[0]->data[pos_attr][0];
> -   float y1 = header->v[1]->data[pos_attr][1] - header->v[0]->data[pos_attr][1];
> -   float z1 = header->v[1]->data[pos_attr][2] - header->v[0]->data[pos_attr][2];
> -
> -   float x2 = header->v[2]->data[pos_attr][0] - header->v[0]->data[pos_attr][0];
> -   float y2 = header->v[2]->data[pos_attr][1] - header->v[0]->data[pos_attr][1];
> -   float z2 = header->v[2]->data[pos_attr][2] - header->v[0]->data[pos_attr][2];
> -
> -   float vx = y1 * z2 - z1 * y2;
> -   float vy = x1 * z2 - z1 * x2;
> -   float vz = x1 * y2 - y1 * x2;
> -
> -   return (vx*vx  + vy*vy + vz*vz) == 0.f;
> -}
> -
> -/**
>    * Emit a post-clip polygon to the next pipeline stage.  The polygon
>    * will be convex and the provoking vertex will always be vertex[0].
>    */
> @@ -247,7 +223,6 @@ static void emit_poly(struct draw_stage *stage,
>      struct prim_header header;
>      unsigned i;
>      ushort edge_first, edge_middle, edge_last;
> -   boolean tri_emitted = FALSE;
>   
>      if (stage->draw->rasterizer->flatshade_first) {
>         edge_first  = DRAW_PIPE_EDGE_FLAG_0;
> @@ -269,7 +244,6 @@ static void emit_poly(struct draw_stage *stage,
>      header.pad = 0;
>   
>      for (i = 2; i < n; i++, header.flags = edge_middle) {
> -      boolean tri_null;
>         /* order the triangle verts to respect the provoking vertex mode */
>         if (stage->draw->rasterizer->flatshade_first) {
>            header.v[0] = inlist[0];  /* the provoking vertex */
> @@ -282,18 +256,6 @@ static void emit_poly(struct draw_stage *stage,
>            header.v[2] = inlist[0];  /* the provoking vertex */
>         }
>   
> -      tri_null = is_tri_null(clipper, &header);
> -      /*
> -       * If we ever generated a tri (regardless if it had area or not),
> -       * skip all subsequent null tris.
> -       * FIXME: I think this logic was hiding bugs elsewhere. It should
> -       * be possible now to always emit all tris.
> -       */
> -      if (tri_null && tri_emitted) {
> -         continue;
> -      }
> -      tri_emitted = TRUE;
> -
>         if (!edgeflags[i-1]) {
>            header.flags &= ~edge_middle;
>         }
> 

Reviewed-by: Brian Paul <brianp at vmware.com>