[Mesa-dev] [PATCH 1/2] Revert "i965: Implement guardband clipping on Sandybridge."

[Oliver McFadden]

On Tue, Oct 02, 2012 at 02:00:39PM +0300, Oliver McFadden wrote:
> This reverts commit 85cd30406ff8414bc6ac6de1064d059a4c564160.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=55523
> Signed-off-by: Oliver McFadden <oliver.mcfadden at linux.intel.com>
> CC: Kenneth Graunke <kenneth at whitecape.org>
> ---

NOTE: This is a candidate for the 9.0 branch.

>  src/mesa/drivers/dri/i965/gen6_clip_state.c     |    1 -
>  src/mesa/drivers/dri/i965/gen6_viewport_state.c |   24 +++++++++-------------
>  2 files changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/gen6_clip_state.c b/src/mesa/drivers/dri/i965/gen6_clip_state.c
> index c34d87e..fc8a2d9 100644
> --- a/src/mesa/drivers/dri/i965/gen6_clip_state.c
> +++ b/src/mesa/drivers/dri/i965/gen6_clip_state.c
> @@ -74,7 +74,6 @@ upload_clip_state(struct brw_context *brw)
>  	     GEN6_CLIP_MODE_NORMAL |
>               nonperspective_barycentric_enable_flag |
>  	     GEN6_CLIP_XY_TEST |
> -	     GEN6_CLIP_GB_TEST |
>  	     userclip << GEN6_USER_CLIP_CLIP_DISTANCES_SHIFT |
>  	     depth_clamp |
>  	     provoking);
> diff --git a/src/mesa/drivers/dri/i965/gen6_viewport_state.c b/src/mesa/drivers/dri/i965/gen6_viewport_state.c
> index 95243f0..f787ac7 100644
> --- a/src/mesa/drivers/dri/i965/gen6_viewport_state.c
> +++ b/src/mesa/drivers/dri/i965/gen6_viewport_state.c
> @@ -33,35 +33,31 @@
>  
>  /* The clip VP defines the guardband region where expensive clipping is skipped
>   * and fragments are allowed to be generated and clipped out cheaply by the SF.
> + *
> + * By setting it to NDC bounds of [-1,1], we don't do GB clipping.  It's
> + * supposed to cause seams to become visible in apps due to shared edges taking
> + * different clip/no clip paths depending on whether the rest of the prim ends
> + * up in the guardband or not.
>   */
>  static void
>  gen6_upload_clip_vp(struct brw_context *brw)
>  {
> -   struct gl_context *ctx = &brw->intel.ctx;
>     struct brw_clipper_viewport *vp;
>  
>     vp = brw_state_batch(brw, AUB_TRACE_CLIP_VP_STATE,
>  			sizeof(*vp), 32, &brw->clip.vp_offset);
>  
> -   /* According to the Sandybridge PRM, Volume 2, Part 1, Section 6.3.8
> -    * "Vertex X,Y Clamping and Quantization", the screen-aligned 2D
> -    * bounding-box of an object must not exceed 16K pixels in either X or Y.
> -    */
> -   const float maximum_post_clamp_delta = 16384;
> -   float gbx = maximum_post_clamp_delta / (float) ctx->Viewport.Width;
> -   float gby = maximum_post_clamp_delta / (float) ctx->Viewport.Height;
> -
> -   vp->xmin = -gbx;
> -   vp->xmax = gbx;
> -   vp->ymin = -gby;
> -   vp->ymax = gby;
> +   vp->xmin = -1.0;
> +   vp->xmax = 1.0;
> +   vp->ymin = -1.0;
> +   vp->ymax = 1.0;
>  
>     brw->state.dirty.cache |= CACHE_NEW_CLIP_VP;
>  }
>  
>  const struct brw_tracked_state gen6_clip_vp = {
>     .dirty = {
> -      .mesa = _NEW_VIEWPORT,
> +      .mesa = 0,
>        .brw = BRW_NEW_BATCH,
>        .cache = 0,
>     },
> -- 
> 1.7.8.6
> 

-- 
Oliver McFadden.