[Mesa-dev] [PATCH 2/2] meta: Use instanced rendering for layered clears.

[Kristian Høgsberg]

On Wed, Aug 13, 2014 at 09:42:50PM -0700, Kenneth Graunke wrote:
> Layered rendering is part of OpenGL 3.2; GL_ARB_draw_instanced is part
> of OpenGL 3.1.  As such, all drivers supporting layered rendering
> already support gl_InstanceID.
> 
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>

Reviewed-by: Kristian Høgsberg <krh at bitplanet.net>

> ---
>  src/mesa/drivers/common/meta.c | 21 +++++----------------
>  1 file changed, 5 insertions(+), 16 deletions(-)
> 
> diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
> index 439c7e2..e0d39c6 100644
> --- a/src/mesa/drivers/common/meta.c
> +++ b/src/mesa/drivers/common/meta.c
> @@ -1527,12 +1527,12 @@ meta_glsl_clear_init(struct gl_context *ctx, struct clear_state *clear)
>  {
>     const char *vs_source =
>        "#extension GL_AMD_vertex_shader_layer : enable\n"
> +      "#extension GL_ARB_draw_instanced : enable\n"
>        "attribute vec4 position;\n"
> -      "uniform int layer;\n"
>        "void main()\n"
>        "{\n"
>        "#ifdef GL_AMD_vertex_shader_layer\n"
> -      "   gl_Layer = layer;\n"
> +      "   gl_Layer = gl_InstanceID;\n"
>        "#endif\n"
>        "   gl_Position = position;\n"
>        "}\n";
> @@ -1568,7 +1568,6 @@ meta_glsl_clear_init(struct gl_context *ctx, struct clear_state *clear)
>     _mesa_LinkProgram(clear->ShaderProg);
>  
>     clear->ColorLocation = _mesa_GetUniformLocation(clear->ShaderProg, "color");
> -   clear->LayerLocation = _mesa_GetUniformLocation(clear->ShaderProg, "layer");
>  
>     has_integer_textures = _mesa_is_gles3(ctx) ||
>        (_mesa_is_desktop_gl(ctx) && ctx->Const.GLSLVersion >= 130);
> @@ -1579,12 +1578,12 @@ meta_glsl_clear_init(struct gl_context *ctx, struct clear_state *clear)
>           ralloc_asprintf(shader_source_mem_ctx,
>                           "#version 130\n"
>                           "#extension GL_AMD_vertex_shader_layer : enable\n"
> +                         "#extension GL_ARB_draw_instanced : enable\n"
>                           "in vec4 position;\n"
> -                         "uniform int layer;\n"
>                           "void main()\n"
>                           "{\n"
>                           "#ifdef GL_AMD_vertex_shader_layer\n"
> -                         "   gl_Layer = layer;\n"
> +                         "   gl_Layer = gl_InstanceID;\n"
>                           "#endif\n"
>                           "   gl_Position = position;\n"
>                           "}\n");
> @@ -1623,8 +1622,6 @@ meta_glsl_clear_init(struct gl_context *ctx, struct clear_state *clear)
>  
>        clear->IntegerColorLocation =
>  	 _mesa_GetUniformLocation(clear->IntegerShaderProg, "color");
> -      clear->IntegerLayerLocation =
> -         _mesa_GetUniformLocation(clear->IntegerShaderProg, "layer");
>     }
>  }
>  
> @@ -1832,15 +1829,7 @@ meta_clear(struct gl_context *ctx, GLbitfield buffers, bool glsl)
>  
>     /* draw quad(s) */
>     if (fb->MaxNumLayers > 0) {
> -      unsigned layer;
> -      assert(glsl && clear->LayerLocation != -1);
> -      for (layer = 0; layer < fb->MaxNumLayers; layer++) {
> -         if (fb->_IntegerColor)
> -            _mesa_Uniform1i(clear->IntegerLayerLocation, layer);
> -         else
> -            _mesa_Uniform1i(clear->LayerLocation, layer);
> -         _mesa_DrawArrays(GL_TRIANGLE_FAN, 0, 4);
> -      }
> +      _mesa_DrawArraysInstanced(GL_TRIANGLE_FAN, 0, 4, fb->MaxNumLayers);
>     } else {
>        _mesa_DrawArrays(GL_TRIANGLE_FAN, 0, 4);
>     }
> -- 
> 2.0.2
> 
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