[Mesa-dev] [PATCH V3 1/4] mesa: Add new variables in gl_context to store sample layout

[Jordan Justen]

On 2014-09-29 16:33:33, Anuj Phogat wrote:
> SampleMap{2,4,8}x variables are used in later patches to implement
> EXT_framebuffer_multisample_blit_scaled extension.
> 
> V2: Use integer array instead of a string.
>     Bump up the comment.
> 
> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
> ---
>  src/mesa/main/mtypes.h | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> index 0d50be8..162dc44 100644
> --- a/src/mesa/main/mtypes.h
> +++ b/src/mesa/main/mtypes.h
> @@ -3608,6 +3608,38 @@ struct gl_constants
>     GLint MaxDepthTextureSamples;
>     GLint MaxIntegerSamples;
>  
> +   /**
> +    * GL_EXT_texture_multisample_blit_scaled implementation assumes that
> +    * samples are laid out in a rectangular grid roughly corresponding to
> +    * sample locations within a pixel. Below SampleMap{2,4,8}x variables
> +    * are used to map indices of rectangular grid to sample numbers within
> +    * a pixel. This mapping of indices to sample numbers must be initialized
> +    * by the driver for the target hardware. For example, if we have the 8X
> +    * MSAA sample number layout (sample positions) for XYZ hardware:
> +    *
> +    *        sample indices layout          sample number layout
> +    *            ---------                      ---------
> +    *            | 0 | 1 |                      | a | b |
> +    *            ---------                      ---------
> +    *            | 2 | 3 |                      | c | d |
> +    *            ---------                      ---------
> +    *            | 4 | 5 |                      | e | f |
> +    *            ---------                      ---------
> +    *            | 6 | 7 |                      | g | h |
> +    *            ---------                      ---------
> +    *
> +    * Where a,b,c,d,e,f,g,h are integers between [0-7].
> +    *
> +    * Then, initialize the SampleMap8x variable for XYZ hardware as shown
> +    * below:
> +    *    SampleMap8x = {a, b, c, d, e, f, g, h};
> +    *
> +    * Follow the logic for other sample counts.
> +    */
> +   unsigned *SampleMap2x;
> +   unsigned *SampleMap4x;
> +   unsigned *SampleMap8x;

Wouldn't uint8_t work given the 0-7 range?

Also, I thought we could include the bytes directly in the structure,
and let the driver write the bytes rather than setting a pointer to
the array.

   uint8_t SampleMap2x[2];
   uint8_t SampleMap4x[4];
   uint8_t SampleMap8x[8];

-Jordan

>     /** GL_ARB_shader_atomic_counters */
>     GLuint MaxAtomicBufferBindings;
>     GLuint MaxAtomicBufferSize;
> -- 
> 1.9.3
> 
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