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

[Yuanhan Liu]

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

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 |   19 +++++++++++++++++--
 2 files changed, 18 insertions(+), 2 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..d354a2b 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;
+   int point_sprite_origin;
 
    /* _NEW_TRANSFORM */
    userclip_active = (ctx->Transform.ClipPlanesEnabled != 0);
@@ -258,8 +259,22 @@ 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;
+   /*
+    * 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 corresponding to rendering
+    * to the default/window FBO.
+    */
+   if (ctx->Point.SpriteOrigin == GL_LOWER_LEFT) {
+      point_sprite_origin = GEN6_SF_POINT_SPRITE_LOWERLEFT;
+      if (render_to_fbo)
+         point_sprite_origin =  GEN6_SF_POINT_SPRITE_UPPERLEFT;
+   } else {
+      point_sprite_origin = GEN6_SF_POINT_SPRITE_UPPERLEFT;
+      if (render_to_fbo)
+         point_sprite_origin =  GEN6_SF_POINT_SPRITE_LOWERLEFT;
+   }
+   dw1 |= point_sprite_origin;
 
    /* _NEW_LIGHT */
    if (ctx->Light.ProvokingVertex != GL_FIRST_VERTEX_CONVENTION) {
-- 
1.7.4.4