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27 * 1x MSAA has a single sample at the center: (0.5, 0.5) -> (0x8, 0x8).
29 * 2x MSAA sample positions are (0.25, 0.25) and (0.75, 0.75):
35 brw_multisample_positions_1x_2x
= 0x0088cc44;
46 brw_multisample_positions_4x
= 0xae2ae662;
49 * Sample positions are based on a solution to the "8 queens" puzzle.
50 * Rationale: in a solution to the 8 queens puzzle, no two queens share
51 * a row, column, or diagonal. This is a desirable property for samples
52 * in a multisampling pattern, because it ensures that the samples are
53 * relatively uniformly distributed through the pixel.
55 * There are several solutions to the 8 queens puzzle (see
56 * http://en.wikipedia.org/wiki/Eight_queens_puzzle). This solution was
57 * chosen because it has a queen close to the center; this should
58 * improve the accuracy of centroid interpolation, since the hardware
59 * implements centroid interpolation by choosing the centermost sample
60 * that overlaps with the primitive being drawn.
62 * Note: from the Ivy Bridge PRM, Vol2 Part1 p304 (3DSTATE_MULTISAMPLE:
65 * "When programming the sample offsets (for NUMSAMPLES_4 or _8 and
66 * MSRASTMODE_xxx_PATTERN), the order of the samples 0 to 3 (or 7
67 * for 8X) must have monotonically increasing distance from the
68 * pixel center. This is required to get the correct centroid
69 * computation in the device."
83 brw_multisample_positions_8x
[] = { 0xdbb39d79, 0x3ff55117 };