[Mesa-dev] [PATCH V2 12/22] i965: expose sample positions
Chris Forbes
chrisf at ijw.co.nz
Mon Feb 4 21:48:46 PST 2013
Moves the definition of the sample positions out of
gen6_emit_3dstate_multisample, and unpacks them in
gen6_get_sample_position.
V2: Be consistent about `sample position` rather than `location`.
Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
---
src/mesa/drivers/dri/i965/brw_context.c | 3 +
src/mesa/drivers/dri/i965/brw_context.h | 5 +
src/mesa/drivers/dri/i965/gen6_multisample_state.c | 117 +++++++++++++--------
3 files changed, 82 insertions(+), 43 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index 9631399..f69085f 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -95,6 +95,9 @@ static void brwInitDriverFunctions(struct intel_screen *screen,
functions->EndTransformFeedback = gen7_end_transform_feedback;
else
functions->EndTransformFeedback = brw_end_transform_feedback;
+
+ if (screen->gen >= 6)
+ functions->GetSamplePosition = gen6_get_sample_position;
}
bool
diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index ce32184..8bb67bc 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -1223,6 +1223,11 @@ void
gen6_emit_3dstate_sample_mask(struct brw_context *brw,
unsigned num_samples, float coverage,
bool coverage_invert, unsigned sample_mask);
+void
+gen6_get_sample_position(struct gl_context *ctx,
+ struct gl_framebuffer *fb,
+ GLuint index,
+ GLfloat *result);
/* gen7_urb.c */
void
diff --git a/src/mesa/drivers/dri/i965/gen6_multisample_state.c b/src/mesa/drivers/dri/i965/gen6_multisample_state.c
index 844aad1..35071e8 100644
--- a/src/mesa/drivers/dri/i965/gen6_multisample_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_multisample_state.c
@@ -26,6 +26,77 @@
#include "brw_context.h"
#include "brw_defines.h"
+/* Sample positions:
+ * 2 6 a e
+ * 2 0
+ * 6 1
+ * a 2
+ * e 3
+ */
+static uint32_t
+sample_positions_4x[] = { 0xae2ae662 };
+/* Sample positions are based on a solution to the "8 queens" puzzle.
+ * Rationale: in a solution to the 8 queens puzzle, no two queens share
+ * a row, column, or diagonal. This is a desirable property for samples
+ * in a multisampling pattern, because it ensures that the samples are
+ * relatively uniformly distributed through the pixel.
+ *
+ * There are several solutions to the 8 queens puzzle (see
+ * http://en.wikipedia.org/wiki/Eight_queens_puzzle). This solution was
+ * chosen because it has a queen close to the center; this should
+ * improve the accuracy of centroid interpolation, since the hardware
+ * implements centroid interpolation by choosing the centermost sample
+ * that overlaps with the primitive being drawn.
+ *
+ * Note: from the Ivy Bridge PRM, Vol2 Part1 p304 (3DSTATE_MULTISAMPLE:
+ * Programming Notes):
+ *
+ * "When programming the sample offsets (for NUMSAMPLES_4 or _8 and
+ * MSRASTMODE_xxx_PATTERN), the order of the samples 0 to 3 (or 7
+ * for 8X) must have monotonically increasing distance from the
+ * pixel center. This is required to get the correct centroid
+ * computation in the device."
+ *
+ * Sample positions:
+ * 1 3 5 7 9 b d f
+ * 1 5
+ * 3 2
+ * 5 6
+ * 7 4
+ * 9 0
+ * b 3
+ * d 1
+ * f 7
+ */
+static uint32_t
+sample_positions_8x[] = { 0xdbb39d79, 0x3ff55117 };
+
+
+void
+gen6_get_sample_position(struct gl_context *ctx,
+ struct gl_framebuffer *fb,
+ GLuint index, GLfloat *result)
+{
+ switch (fb->Visual.samples) {
+ case 1:
+ result[0] = result[1] = 0.5f;
+ break;
+ case 4: {
+ uint8_t val = (uint8_t)(sample_positions_4x[0] >> (8*index));
+ result[0] = (val & 0xf) / 16.0f;
+ result[1] = ((val >> 4) & 0xf) / 16.0f;
+ break;
+ }
+ case 8: {
+ uint8_t val = (uint8_t)(sample_positions_8x[index>>2] >> (8*(index & 3)));
+ result[0] = (val & 0xf) / 16.0f;
+ result[1] = ((val >> 4) & 0xf) / 16.0f;
+ break;
+ }
+ default:
+ assert(!"Not implemented");
+ }
+}
/**
* 3DSTATE_MULTISAMPLE
@@ -47,52 +118,12 @@ gen6_emit_3dstate_multisample(struct brw_context *brw,
break;
case 4:
number_of_multisamples = MS_NUMSAMPLES_4;
- /* Sample positions:
- * 2 6 a e
- * 2 0
- * 6 1
- * a 2
- * e 3
- */
- sample_positions_3210 = 0xae2ae662;
+ sample_positions_3210 = sample_positions_4x[0];
break;
case 8:
number_of_multisamples = MS_NUMSAMPLES_8;
- /* Sample positions are based on a solution to the "8 queens" puzzle.
- * Rationale: in a solution to the 8 queens puzzle, no two queens share
- * a row, column, or diagonal. This is a desirable property for samples
- * in a multisampling pattern, because it ensures that the samples are
- * relatively uniformly distributed through the pixel.
- *
- * There are several solutions to the 8 queens puzzle (see
- * http://en.wikipedia.org/wiki/Eight_queens_puzzle). This solution was
- * chosen because it has a queen close to the center; this should
- * improve the accuracy of centroid interpolation, since the hardware
- * implements centroid interpolation by choosing the centermost sample
- * that overlaps with the primitive being drawn.
- *
- * Note: from the Ivy Bridge PRM, Vol2 Part1 p304 (3DSTATE_MULTISAMPLE:
- * Programming Notes):
- *
- * "When programming the sample offsets (for NUMSAMPLES_4 or _8 and
- * MSRASTMODE_xxx_PATTERN), the order of the samples 0 to 3 (or 7
- * for 8X) must have monotonically increasing distance from the
- * pixel center. This is required to get the correct centroid
- * computation in the device."
- *
- * Sample positions:
- * 1 3 5 7 9 b d f
- * 1 5
- * 3 2
- * 5 6
- * 7 4
- * 9 0
- * b 3
- * d 1
- * f 7
- */
- sample_positions_3210 = 0xdbb39d79;
- sample_positions_7654 = 0x3ff55117;
+ sample_positions_3210 = sample_positions_8x[0];
+ sample_positions_7654 = sample_positions_8x[1];
break;
default:
assert(!"Unrecognized num_samples in gen6_emit_3dstate_multisample");
--
1.8.1.2
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