r300g: add support for 3D NPOT textures without mipmapping

The driver actually creates a 3D texture aligned to POT and does all
the magic with texture coordinates in the fragment shader. It first
emulates REPEAT and MIRRORED wrap modes in the fragment shader to get
the coordinates into the range [0, 1]. (already done for 2D NPOT)
Then it scales them to get the coordinates of the NPOT subtexture.

NPOT textures are now less of a lie and we can at least display
something meaningful even for the 3D ones.

Supported wrap modes:
- REPEAT
- MIRRORED_REPEAT
- CLAMP_TO_EDGE (NEAREST filtering only)
- MIRROR_CLAMP_TO_EDGE (NEAREST filtering only)
- The behavior of other CLAMP modes is undefined on borders, but they usually
  give results very close to CLAMP_TO_EDGE with mirroring working perfectly.

This fixes:
- piglit/fbo-3d
- piglit/tex3d-npot

1 files changed, 3 insertions, 0 deletions

diff --git a/src/gallium/drivers/r300/r300_fs.c b/src/gallium/drivers/r300/r300_fs.c
index 3f89987897..d9d4a9304d 100644
--- a/src/gallium/drivers/r300/r300_fs.c
+++ b/src/gallium/drivers/r300/r300_fs.c
@@ -200,6 +200,9 @@ static void get_external_state(
             default:
                 state->unit[i].wrap_mode = RC_WRAP_NONE;
             }
+
+            if (t->desc.b.b.target == PIPE_TEXTURE_3D)
+                state->unit[i].clamp_and_scale_before_fetch = TRUE;
         }
     }
 }