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-rw-r--r--src/mesa/drivers/dri/i965/brw_multisample_state.h43
1 files changed, 20 insertions, 23 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_multisample_state.h b/src/mesa/drivers/dri/i965/brw_multisample_state.h
index 42a7fd35121..db59af2affb 100644
--- a/src/mesa/drivers/dri/i965/brw_multisample_state.h
+++ b/src/mesa/drivers/dri/i965/brw_multisample_state.h
@@ -24,6 +24,15 @@
#include <stdint.h>
/**
+ * Note: There are no standard multisample positions defined in OpenGL
+ * specifications. Implementations have the freedom to pick the positions
+ * which give plausible results. But the Vulkan specification does define
+ * standard sample positions. So, we decided to pick the same pattern in
+ * OpenGL as in Vulkan to keep it uniform across drivers and also to avoid
+ * breaking applications which rely on this standard pattern.
+ */
+
+/**
* 1x MSAA has a single sample at the center: (0.5, 0.5) -> (0x8, 0x8).
*
* 2x MSAA sample positions are (0.25, 0.25) and (0.75, 0.75):
@@ -46,22 +55,10 @@ static const uint32_t
brw_multisample_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.
+ * Sample positions:
*
- * Note: from the Ivy Bridge PRM, Vol2 Part1 p304 (3DSTATE_MULTISAMPLE:
+ * 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
@@ -70,17 +67,17 @@ brw_multisample_positions_4x = 0xae2ae662;
*
* 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
+ * 1 7
+ * 3 3
+ * 5 0
+ * 7 5
+ * 9 2
+ * b 1
+ * d 4
+ * f 6
*/
static const uint32_t
-brw_multisample_positions_8x[] = { 0xdbb39d79, 0x3ff55117 };
+brw_multisample_positions_8x[] = { 0x53d97b95, 0xf1bf173d };
/**
* Sample positions: