[Mesa-dev] [PATCH] intel/common: Improve the comments for sample positions

[Lionel Landwerlin]

Nice!

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

On 13/10/17 06:58, Jason Ekstrand wrote:
> These are pulled directly from brw_multisample_state.h
> ---
>   src/intel/common/gen_sample_positions.h | 65 +++++++++++++++++++++++++++++++++
>   1 file changed, 65 insertions(+)
>
> diff --git a/src/intel/common/gen_sample_positions.h b/src/intel/common/gen_sample_positions.h
> index b86a7d8..f0ce95d 100644
> --- a/src/intel/common/gen_sample_positions.h
> +++ b/src/intel/common/gen_sample_positions.h
> @@ -23,16 +23,38 @@
>   #ifndef GEN_SAMPLE_POSITIONS_H
>   #define GEN_SAMPLE_POSITIONS_H
>   
> +/*
> + * This file defines the standard multisample positions used by both GL and
> + * Vulkan.  These correspond to the Vulkan "standard sample locations".
> + */
> +
> +/**
> + * 1x MSAA has a single sample at the center: (0.5, 0.5) -> (0x8, 0x8).
> + */
>   #define GEN_SAMPLE_POS_1X(prefix) \
>   prefix##0XOffset   = 0.5; \
>   prefix##0YOffset   = 0.5;
>   
> +/**
> + * 2x MSAA sample positions are (0.25, 0.25) and (0.75, 0.75):
> + *   4 c
> + * 4 0
> + * c   1
> + */
>   #define GEN_SAMPLE_POS_2X(prefix) \
>   prefix##0XOffset   = 0.25; \
>   prefix##0YOffset   = 0.25; \
>   prefix##1XOffset   = 0.75; \
>   prefix##1YOffset   = 0.75;
>   
> +/**
> + * Sample positions:
> + *   2 6 a e
> + * 2   0
> + * 6       1
> + * a 2
> + * e     3
> + */
>   #define GEN_SAMPLE_POS_4X(prefix) \
>   prefix##0XOffset   = 0.375; \
>   prefix##0YOffset   = 0.125; \
> @@ -43,6 +65,28 @@ prefix##2YOffset   = 0.625; \
>   prefix##3XOffset   = 0.625; \
>   prefix##3YOffset   = 0.875;
>   
> +/**
> + * Sample positions:
> + *
> + * 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               7
> + * 3     3
> + * 5         0
> + * 7 5
> + * 9             2
> + * b       1
> + * d   4
> + * f           6
> + */
>   #define GEN_SAMPLE_POS_8X(prefix) \
>   prefix##0XOffset   = 0.5625; \
>   prefix##0YOffset   = 0.3125; \
> @@ -61,6 +105,27 @@ prefix##6YOffset   = 0.9375; \
>   prefix##7XOffset   = 0.9375; \
>   prefix##7YOffset   = 0.0625;
>   
> +/**
> + * Sample positions:
> + *
> + *    0 1 2 3 4 5 6 7 8 9 a b c d e f
> + * 0   15
> + * 1                  9
> + * 2         10
> + * 3                        7
> + * 4                               13
> + * 5                1
> + * 6        4
> + * 7                          3
> + * 8 12
> + * 9                    0
> + * a            2
> + * b                            6
> + * c     11
> + * d                      5
> + * e              8
> + * f                             14
> + */
>   #define GEN_SAMPLE_POS_16X(prefix) \
>   prefix##0XOffset   = 0.5625; \
>   prefix##0YOffset   = 0.5625; \