OpenGL: simple 2D shader with flat color

Flat color means each primitive will use color from the provoking
vertex.

5 files changed, 50 insertions, 0 deletions

diff --git a/source/blender/gpu/CMakeLists.txt b/source/blender/gpu/CMakeLists.txt
index 6bdac68831d..467b76a4ef4 100644
--- a/source/blender/gpu/CMakeLists.txt
+++ b/source/blender/gpu/CMakeLists.txt
@@ -102,6 +102,8 @@ set(SRC
 
 data_to_c_simple(shaders/gpu_shader_2D_uniform_color_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_2D_uniform_color_frag.glsl SRC)
+data_to_c_simple(shaders/gpu_shader_2D_flat_color_vert.glsl SRC)
+data_to_c_simple(shaders/gpu_shader_2D_flat_color_frag.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_2D_smooth_color_vert.glsl SRC)
 data_to_c_simple(shaders/gpu_shader_2D_smooth_color_frag.glsl SRC)
 
diff --git a/source/blender/gpu/GPU_shader.h b/source/blender/gpu/GPU_shader.h
index 0e29780d516..ebc90df3a11 100644
--- a/source/blender/gpu/GPU_shader.h
+++ b/source/blender/gpu/GPU_shader.h
@@ -92,6 +92,7 @@ typedef enum GPUBuiltinShader {
 
 	/* for simple drawing */
 	GPU_SHADER_2D_UNIFORM_COLOR,
+	GPU_SHADER_2D_FLAT_COLOR,
 	GPU_SHADER_2D_SMOOTH_COLOR,
 } GPUBuiltinShader;
 
diff --git a/source/blender/gpu/intern/gpu_shader.c b/source/blender/gpu/intern/gpu_shader.c
index 67f6545351e..1b3392e8692 100644
--- a/source/blender/gpu/intern/gpu_shader.c
+++ b/source/blender/gpu/intern/gpu_shader.c
@@ -48,6 +48,8 @@
 /* Non-generated shaders */
 extern char datatoc_gpu_shader_2D_uniform_color_vert_glsl[];
 extern char datatoc_gpu_shader_2D_uniform_color_frag_glsl[];
+extern char datatoc_gpu_shader_2D_flat_color_vert_glsl[];
+extern char datatoc_gpu_shader_2D_flat_color_frag_glsl[];
 extern char datatoc_gpu_shader_2D_smooth_color_vert_glsl[];
 extern char datatoc_gpu_shader_2D_smooth_color_frag_glsl[];
 
@@ -77,6 +79,7 @@ static struct GPUShadersGlobal {
 		GPUShader *fx_shaders[MAX_FX_SHADERS * 2];
 		/* for simple drawing */
 		GPUShader *uniform_color_2D;
+		GPUShader *flat_color_2D;
 		GPUShader *smooth_color_2D;
 	} shaders;
 } GG = {{NULL}};
@@ -638,6 +641,14 @@ GPUShader *GPU_shader_get_builtin_shader(GPUBuiltinShader shader)
 				        NULL, NULL, NULL, 0, 0, 0);
 			retval = GG.shaders.uniform_color_2D;
 			break;
+		case GPU_SHADER_2D_FLAT_COLOR:
+			if (!GG.shaders.flat_color_2D)
+				GG.shaders.flat_color_2D = GPU_shader_create(
+				        datatoc_gpu_shader_2D_flat_color_vert_glsl,
+				        datatoc_gpu_shader_2D_flat_color_frag_glsl,
+				        NULL, NULL, NULL, 0, 0, 0);
+			retval = GG.shaders.flat_color_2D;
+			break;
 		case GPU_SHADER_2D_SMOOTH_COLOR:
 			if (!GG.shaders.smooth_color_2D)
 				GG.shaders.smooth_color_2D = GPU_shader_create(
@@ -762,6 +773,11 @@ void GPU_shader_free_builtin_shaders(void)
 		GG.shaders.uniform_color_2D = NULL;
 	}
 
+	if (GG.shaders.flat_color_2D) {
+		GPU_shader_free(GG.shaders.flat_color_2D);
+		GG.shaders.flat_color_2D = NULL;
+	}
+
 	if (GG.shaders.smooth_color_2D) {
 		GPU_shader_free(GG.shaders.smooth_color_2D);
 		GG.shaders.smooth_color_2D = NULL;
diff --git a/source/blender/gpu/shaders/gpu_shader_2D_flat_color_frag.glsl b/source/blender/gpu/shaders/gpu_shader_2D_flat_color_frag.glsl
new file mode 100644
index 00000000000..91097d24cb2
--- /dev/null
+++ b/source/blender/gpu/shaders/gpu_shader_2D_flat_color_frag.glsl
@@ -0,0 +1,13 @@
+
+#if __VERSION__ == 120
+  flat varying vec4 finalColor;
+  #define fragColor gl_FragColor
+#else
+  flat in vec4 finalColor;
+  out vec4 fragColor;
+#endif
+
+void main()
+{
+	fragColor = finalColor;
+}
diff --git a/source/blender/gpu/shaders/gpu_shader_2D_flat_color_vert.glsl b/source/blender/gpu/shaders/gpu_shader_2D_flat_color_vert.glsl
new file mode 100644
index 00000000000..aa1eba470ab
--- /dev/null
+++ b/source/blender/gpu/shaders/gpu_shader_2D_flat_color_vert.glsl
@@ -0,0 +1,18 @@
+
+#if __VERSION__ == 120
+  attribute vec2 pos;
+  attribute vec4 color;
+
+  flat varying vec4 finalColor;
+#else
+  in vec2 pos;
+  in vec4 color;
+
+  flat out vec4 finalColor;
+#endif
+
+void main()
+{
+	gl_Position = gl_ModelViewProjectionMatrix * vec4(pos, 0.0, 1.0);
+	finalColor = color;
+}