[Mesa-dev] [PATCH] i965: fix inverted point sprite origin when rendering to FBO

[Jonathan Coome]

On 19/01/2012 23:48, Yuanhan Liu wrote:
> When rendering to FBO, rendering is inverted. At the same time, we would
> also make sure the point sprite origin is inverted. Or, we will get an
> inverted result correspoinding to rendering to the default winsys FBO.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44613
> 
> NOTE: This is a candidate for stable release branches.
> 
> v2: add the simliar logic to ivb, too (comments from Ian)
>     simplify the logic operation (comments from Brian)
> 
> v3: pick a better comment from Eric
>     use != for the logic instead of ^ (comments from Ian)
> 
> Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
> ---
>  src/mesa/drivers/dri/i965/brw_defines.h   |    1 +
>  src/mesa/drivers/dri/i965/gen6_sf_state.c |   13 +++++++++++--
>  src/mesa/drivers/dri/i965/gen7_sf_state.c |   18 +++++++++++++++---
>  3 files changed, 27 insertions(+), 5 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
> index 4d90a99..029be87 100644
> --- a/src/mesa/drivers/dri/i965/brw_defines.h
> +++ b/src/mesa/drivers/dri/i965/brw_defines.h
> @@ -1128,6 +1128,7 @@ enum brw_message_target {
>  /* DW1 (for gen6) */
>  # define GEN6_SF_NUM_OUTPUTS_SHIFT			22
>  # define GEN6_SF_SWIZZLE_ENABLE				(1 << 21)
> +# define GEN6_SF_POINT_SPRITE_UPPERLEFT			(0 << 20)
>  # define GEN6_SF_POINT_SPRITE_LOWERLEFT			(1 << 20)
>  # define GEN6_SF_URB_ENTRY_READ_LENGTH_SHIFT		11
>  # define GEN6_SF_URB_ENTRY_READ_OFFSET_SHIFT		4
> diff --git a/src/mesa/drivers/dri/i965/gen6_sf_state.c b/src/mesa/drivers/dri/i965/gen6_sf_state.c
> index 548c5a3..163b54c 100644
> --- a/src/mesa/drivers/dri/i965/gen6_sf_state.c
> +++ b/src/mesa/drivers/dri/i965/gen6_sf_state.c
> @@ -129,6 +129,7 @@ upload_sf_state(struct brw_context *brw)
>     float point_size;
>     uint16_t attr_overrides[FRAG_ATTRIB_MAX];
>     bool userclip_active;
> +   uint32_t point_sprite_origin;
>  
>     /* _NEW_TRANSFORM */
>     userclip_active = (ctx->Transform.ClipPlanesEnabled != 0);
> @@ -258,8 +259,16 @@ upload_sf_state(struct brw_context *brw)
>     /* Clamp to the hardware limits and convert to fixed point */
>     dw4 |= U_FIXED(CLAMP(point_size, 0.125, 255.875), 3);
>  
> -   if (ctx->Point.SpriteOrigin == GL_LOWER_LEFT)
> -      dw1 |= GEN6_SF_POINT_SPRITE_LOWERLEFT;
> +   /*
> +    * Window coordinates in an FBO are inverted, which means point
> +    * sprite origin must be inverted, too.
> +    */
> +   if ((ctx->Point.SpriteOrigin == GL_LOWER_LEFT) != render_to_fbo) {
> +      point_sprite_origin = GEN6_SF_POINT_SPRITE_LOWERLEFT;
> +   } else {
> +      point_sprite_origin = GEN6_SF_POINT_SPRITE_UPPERLEFT;
> +   }
> +   dw1 |= point_sprite_origin;
>  
>     /* _NEW_LIGHT */
>     if (ctx->Light.ProvokingVertex != GL_FIRST_VERTEX_CONVENTION) {
> diff --git a/src/mesa/drivers/dri/i965/gen7_sf_state.c b/src/mesa/drivers/dri/i965/gen7_sf_state.c
> index 7691cb2..da7ef81 100644
> --- a/src/mesa/drivers/dri/i965/gen7_sf_state.c
> +++ b/src/mesa/drivers/dri/i965/gen7_sf_state.c
> @@ -48,6 +48,9 @@ upload_sbe_state(struct brw_context *brw)
>     int urb_entry_read_offset = 1;
>     bool userclip_active = (ctx->Transform.ClipPlanesEnabled != 0);
>     uint16_t attr_overrides[FRAG_ATTRIB_MAX];
> +   /* _NEW_BUFFERS */
> +   bool render_to_fbo = ctx->DrawBuffer->Name != 0;
> +   uint32_t point_sprite_origin;
>  
>     brw_compute_vue_map(&vue_map, intel, userclip_active, vs_outputs_written);
>     urb_entry_read_length = (vue_map.num_slots + 1)/2 - urb_entry_read_offset;
> @@ -65,9 +68,18 @@ upload_sbe_state(struct brw_context *brw)
>        urb_entry_read_length << GEN7_SBE_URB_ENTRY_READ_LENGTH_SHIFT |
>        urb_entry_read_offset << GEN7_SBE_URB_ENTRY_READ_OFFSET_SHIFT;
>  
> -   /* _NEW_POINT */
> -   if (ctx->Point.SpriteOrigin == GL_LOWER_LEFT)
> -      dw1 |= GEN6_SF_POINT_SPRITE_LOWERLEFT;
> +   /* _NEW_POINT
> +    *
> +    * Window coordinates in an FBO are inverted, which means point
> +    * sprite origin must be inverted.
> +    */
> +   if ((ctx->Point.SpriteOrigin == GL_LOWER_LEFT) != render_to_fbo) {
> +      point_sprite_origin = GEN6_SF_POINT_SPRITE_LOWERLEFT;
> +   } else {
> +      point_sprite_origin = GEN6_SF_POINT_SPRITE_UPPERLEFT;
> +   }
> +   dw1 |= point_sprite_origin;
> +
>  
>     dw10 = 0;
>     dw11 = 0;

Is there any need for GEN6_SF_POINT_SPRITE_UPPERLEFT? It's basically 0,
so the | operation with dw1 won't have any effect, and you could remove
the else clauses. And if you wanted to clear the bit, I think you'd need
to do something like this instead:

if ((ctx->Point.SpriteOrigin == GL_LOWER_LEFT) != render_to_fbo) {
	dw1 |= GEN6_SF_POINT_SPRITE_LOWERLEFT;
} else {
	dw1 &= ~GEN6_SF_POINT_SPRITE_LOWERLEFT;
}

-Jonathan