diff options
| -rw-r--r-- | src/mesa/drivers/dri/i965/brw_multisample_state.h | 43 |
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: |