GPU: use ifdef for flat shader

source/blender/gpu/CMakeLists.txt

@@ -128,7 +128,6 @@ data_to_c_simple(shaders/gpu_shader_uniform_color_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_checker_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_diag_stripes_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_simple_lighting_frag.glsl SRC)
-data_to_c_simple(shaders/gpu_shader_simple_lighting_flat_color_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_simple_lighting_smooth_color_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_simple_lighting_smooth_color_alpha_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_flat_color_frag.glsl SRC)
@@ -158,7 +157,6 @@ data_to_c_simple(shaders/gpu_shader_3D_flat_color_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_3D_line_dashed_legacy_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_3D_line_dashed_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_3D_smooth_color_vert.glsl SRC)
-data_to_c_simple(shaders/gpu_shader_3D_normal_flat_color_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_3D_normal_smooth_color_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_3D_smooth_color_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_3D_passthrough_vert.glsl SRC)

source/blender/gpu/intern/gpu_shader.c

@@ -673,7 +673,8 @@ GPUShader *GPU_shader_get_builtin_shader(GPUBuiltinShader shader)
 		                               datatoc_gpu_shader_edges_overlay_frag_glsl,
 		                               datatoc_gpu_shader_edges_overlay_geom_glsl },
 		[GPU_SHADER_SIMPLE_LIGHTING] = { datatoc_gpu_shader_3D_normal_vert_glsl, datatoc_gpu_shader_simple_lighting_frag_glsl },
-		[GPU_SHADER_SIMPLE_LIGHTING_FLAT_COLOR] = { datatoc_gpu_shader_3D_normal_flat_color_vert_glsl, datatoc_gpu_shader_simple_lighting_flat_color_frag_glsl },
+		/* Use 'USE_FLAT_NORMAL' to make flat shader from smooth  */
+		[GPU_SHADER_SIMPLE_LIGHTING_FLAT_COLOR] = { datatoc_gpu_shader_3D_normal_smooth_color_vert_glsl, datatoc_gpu_shader_simple_lighting_smooth_color_frag_glsl },
 		[GPU_SHADER_SIMPLE_LIGHTING_SMOOTH_COLOR] = { datatoc_gpu_shader_3D_normal_smooth_color_vert_glsl, datatoc_gpu_shader_simple_lighting_smooth_color_frag_glsl },
 		[GPU_SHADER_SIMPLE_LIGHTING_SMOOTH_COLOR_ALPHA] = { datatoc_gpu_shader_3D_normal_smooth_color_vert_glsl, datatoc_gpu_shader_simple_lighting_smooth_color_alpha_frag_glsl },
 
@@ -806,6 +807,9 @@ GPUShader *GPU_shader_get_builtin_shader(GPUBuiltinShader shader)
 			case GPU_SHADER_3D_FLAT_COLOR_U32:
 				defines = "#define USE_COLOR_U32;\n";
 				break;
+			case GPU_SHADER_SIMPLE_LIGHTING_FLAT_COLOR:
+				defines = "#define USE_FLAT_NORMAL;\n";
+				break;
 			default:
 				break;
 		}

source/blender/gpu/shaders/gpu_shader_3D_normal_flat_color_vert.glsl

@@ -1,26 +0,0 @@
-
-uniform mat4 ModelViewProjectionMatrix;
-uniform mat3 NormalMatrix;
-
-#if __VERSION__ == 120
-  attribute vec3 pos;
-  attribute vec3 nor;
-  attribute vec4 color;
-
-  flat varying vec4 finalColor;
-  flat varying vec3 normal;
-#else
-  in vec3 pos;
-  in vec3 nor;
-  in vec4 color;
-
-  flat out vec3 normal;
-  flat out vec4 finalColor;
-#endif
-
-void main()
-{
-	normal = normalize(NormalMatrix * nor);
-	gl_Position = ModelViewProjectionMatrix * vec4(pos, 1.0);
-	finalColor = color;
-}

source/blender/gpu/shaders/gpu_shader_3D_normal_smooth_color_vert.glsl

@@ -7,15 +7,25 @@ uniform mat3 NormalMatrix;
   attribute vec3 nor;
   attribute vec4 color;
 
+#  ifdef USE_FLAT_NORMAL
+  flat varying vec4 finalColor;
+  flat varying vec3 normal;
+#  else
   varying vec4 finalColor;
   varying vec3 normal;
+#  endif
 #else
   in vec3 pos;
   in vec3 nor;
   in vec4 color;
 
+#  ifdef USE_FLAT_NORMAL
+  flat out vec3 normal;
+  flat out vec4 finalColor;
+#  else
   out vec3 normal;
   out vec4 finalColor;
+#  endif
 #endif
 
 void main()

source/blender/gpu/shaders/gpu_shader_simple_lighting_flat_color_frag.glsl

@@ -1,17 +0,0 @@
-
-uniform vec3 light;
-
-#if __VERSION__ == 120
-  flat varying vec3 normal;
-  flat varying vec4 finalColor;
-  #define fragColor gl_FragColor
-#else
-  flat in vec3 normal;
-  flat in vec4 finalColor;
-  out vec4 fragColor;
-#endif
-
-void main()
-{
-	fragColor = finalColor * max(0.0, dot(normalize(normal), light));
-}

source/blender/gpu/shaders/gpu_shader_simple_lighting_smooth_color_frag.glsl

@@ -2,12 +2,22 @@
 uniform vec3 light;
 
 #if __VERSION__ == 120
+#  ifdef USE_FLAT_NORMAL
+  flat varying vec3 normal;
+  flat varying vec4 finalColor;
+#  else
   varying vec3 normal;
   varying vec4 finalColor;
+#  endif
   #define fragColor gl_FragColor
 #else
+#  ifdef USE_FLAT_NORMAL
+  flat in vec3 normal;
+  flat in vec4 finalColor;
+#  else
   in vec3 normal;
   in vec4 finalColor;
+#  endif
   out vec4 fragColor;
 #endif