From 46737cebd337200f8b88ba9081796fa0f94e9143 Mon Sep 17 00:00:00 2001 From: Anuj Phogat Date: Mon, 19 May 2014 11:55:01 -0700 Subject: [PATCH] meta: Use gl_FragColor to output color values to all the draw buffers _mesa_meta_setup_blit_shader() currently generates a fragment shader which, irrespective of the number of draw buffers, writes the color to only one 'out' variable. Current shader rely on an undefined behavior and possibly works by chance. From OpenGL 4.0 spec, page 256: "If a fragment shader writes to gl_FragColor, DrawBuffers specifies a set of draw buffers into which the single fragment color defined by gl_FragColor is written. If a fragment shader writes to gl_FragData, or a user-defined varying out variable, DrawBuffers specifies a set of draw buffers into which each of the multiple output colors defined by these variables are separately written. If a fragment shader writes to none of gl_FragColor, gl_FragData, nor any user defined varying out variables, the values of the fragment colors following shader execution are undefined, and may differ for each fragment color." OpenGL 4.4 spec, page 463, added an additional line in this section: "If some, but not all user-defined output variables are written, the values of fragment colors corresponding to unwritten variables are similarly undefined." V2: Write color output to gl_FragColor instead of writing to multiple 'out' variables. This'll avoid recompiling the shader every time draw buffers count is updated. Cc: Signed-off-by: Anuj Phogat Reviewed-by: Matt Turner Reviewed-by: Kenneth Graunke --- src/mesa/drivers/common/meta.c | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-) diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c index 1b2fe8a..fec0d2b 100644 --- a/src/mesa/drivers/common/meta.c +++ b/src/mesa/drivers/common/meta.c @@ -246,7 +246,6 @@ _mesa_meta_setup_blit_shader(struct gl_context *ctx, void *const mem_ctx = ralloc_context(NULL); struct blit_shader *shader = choose_blit_shader(target, table); const char *vs_input, *vs_output, *fs_input, *vs_preprocess, *fs_preprocess; - const char *fs_output_var, *fs_output_var_decl; if (ctx->Const.GLSLVersion < 130) { vs_preprocess = ""; @@ -254,16 +253,12 @@ _mesa_meta_setup_blit_shader(struct gl_context *ctx, vs_output = "varying"; fs_preprocess = "#extension GL_EXT_texture_array : enable"; fs_input = "varying"; - fs_output_var_decl = ""; - fs_output_var = "gl_FragColor"; } else { vs_preprocess = "#version 130"; vs_input = "in"; vs_output = "out"; fs_preprocess = "#version 130"; fs_input = "in"; - fs_output_var_decl = "out vec4 out_color;"; - fs_output_var = "out_color"; shader->func = "texture"; } @@ -291,15 +286,13 @@ _mesa_meta_setup_blit_shader(struct gl_context *ctx, "#extension GL_ARB_texture_cube_map_array: enable\n" "uniform %s texSampler;\n" "%s vec4 texCoords;\n" - "%s\n" "void main()\n" "{\n" - " vec4 color = %s(texSampler, %s);\n" - " %s = color;\n" - " gl_FragDepth = color.x;\n" + " gl_FragColor = %s(texSampler, %s);\n" + " gl_FragDepth = gl_FragColor.x;\n" "}\n", - fs_preprocess, shader->type, fs_input, fs_output_var_decl, - shader->func, shader->texcoords, fs_output_var); + fs_preprocess, shader->type, fs_input, + shader->func, shader->texcoords); _mesa_meta_compile_and_link_program(ctx, vs_source, fs_source, ralloc_asprintf(mem_ctx, "%s blit", -- 2.7.4