Flat shading for basic shader

The purpose of the patch is to replace deprecated  glShadeModel.

To decrease glShadeModel calls I've set GL_SMOOTH by default

Reviewers: merwin, brecht

Reviewed By: brecht

Subscribers: blueprintrandom, Evgeny_Rodygin, AlexKowel, yurikovelenov

Differential Revision: https://developer.blender.org/D1958

6 files changed, 38 insertions, 9 deletions

diff --git a/source/blender/gpu/GPU_basic_shader.h b/source/blender/gpu/GPU_basic_shader.h
index 8e38ac8876f..6c78aec2ec7 100644
--- a/source/blender/gpu/GPU_basic_shader.h
+++ b/source/blender/gpu/GPU_basic_shader.h
@@ -51,7 +51,8 @@ typedef enum GPUBasicShaderOption {
 	GPU_SHADER_SOLID_LIGHTING =   (1 << 5),   /* use faster lighting (set automatically) */
 	GPU_SHADER_STIPPLE =          (1 << 6),   /* use stipple */
 	GPU_SHADER_LINE =             (1 << 7),   /* draw lines */
-	GPU_SHADER_OPTIONS_NUM = 8,
+	GPU_SHADER_FLAT_NORMAL =      (1 << 8),   /* use flat normals */
+	GPU_SHADER_OPTIONS_NUM = 9,
 	GPU_SHADER_OPTION_COMBINATIONS = (1 << GPU_SHADER_OPTIONS_NUM)
 } GPUBasicShaderOption;
 
diff --git a/source/blender/gpu/intern/gpu_basic_shader.c b/source/blender/gpu/intern/gpu_basic_shader.c
index 4be50a078b7..c5a2d07bdc8 100644
--- a/source/blender/gpu/intern/gpu_basic_shader.c
+++ b/source/blender/gpu/intern/gpu_basic_shader.c
@@ -376,6 +376,8 @@ static GPUShader *gpu_basic_shader(int options)
 			strcat(defines, "#define DRAW_LINE\n");
 			geom_glsl = datatoc_gpu_shader_basic_geom_glsl;
 		}
+		if (options & GPU_SHADER_FLAT_NORMAL)
+			strcat(defines, "#define USE_FLAT_NORMAL\n");
 		if (options & GPU_SHADER_SOLID_LIGHTING)
 			strcat(defines, "#define USE_SOLID_LIGHTING\n");
 		else if (options & GPU_SHADER_LIGHTING)
@@ -507,6 +509,12 @@ void GPU_basic_shader_bind(int options)
 				glDisable(GL_POLYGON_STIPPLE);
 		}
 
+		if (options & GPU_SHADER_FLAT_NORMAL) {
+			glShadeModel(GL_FLAT);
+		}
+		else {
+			glShadeModel(GL_SMOOTH);
+		}
 	}
 
 	GPU_MATERIAL_STATE.bound_options = options;
diff --git a/source/blender/gpu/intern/gpu_buffers.c b/source/blender/gpu/intern/gpu_buffers.c
index e8605e27595..35bfc687052 100644
--- a/source/blender/gpu/intern/gpu_buffers.c
+++ b/source/blender/gpu/intern/gpu_buffers.c
@@ -1863,10 +1863,14 @@ void GPU_draw_pbvh_buffers(GPU_PBVH_Buffers *buffers, DMSetMaterial setMaterial,
 			GPU_buffer_bind(buffers->index_buf, GPU_BINDING_INDEX);
 		}
 
-		if (wireframe)
+		if (wireframe) {
 			glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
-		else
-			glShadeModel((buffers->smooth || buffers->face_indices_len) ? GL_SMOOTH : GL_FLAT);
+		}
+		else {
+			bound_options = GPU_basic_shader_bound_options();
+			GPU_basic_shader_bind(bound_options | ((buffers->smooth || buffers->face_indices_len) ?
+			                      0 : GPU_SHADER_FLAT_NORMAL));
+		}
 
 		if (buffers->tot_quad) {
 			const char *offset = base;
diff --git a/source/blender/gpu/intern/gpu_draw.c b/source/blender/gpu/intern/gpu_draw.c
index b6f977d12ab..f998dc9904e 100644
--- a/source/blender/gpu/intern/gpu_draw.c
+++ b/source/blender/gpu/intern/gpu_draw.c
@@ -1995,8 +1995,9 @@ int GPU_object_material_bind(int nr, void *attribs)
 		}
 		else {
 			/* or do fixed function opengl material */
-			GPU_basic_shader_colors(GMS.matbuf[nr].diff,
-				GMS.matbuf[nr].spec, GMS.matbuf[nr].hard, GMS.matbuf[nr].alpha);
+			GPU_basic_shader_colors(
+			        GMS.matbuf[nr].diff,
+			        GMS.matbuf[nr].spec, GMS.matbuf[nr].hard, GMS.matbuf[nr].alpha);
 
 			if (GMS.two_sided_lighting)
 				GPU_basic_shader_bind(GPU_SHADER_LIGHTING | GPU_SHADER_TWO_SIDED);
@@ -2290,8 +2291,6 @@ void GPU_state_init(void)
 	/* scaling matrices */
 	glEnable(GL_NORMALIZE);
 
-	glShadeModel(GL_FLAT);
-
 	glDisable(GL_ALPHA_TEST);
 	glDisable(GL_BLEND);
 	glDisable(GL_DEPTH_TEST);
diff --git a/source/blender/gpu/shaders/gpu_shader_basic_frag.glsl b/source/blender/gpu/shaders/gpu_shader_basic_frag.glsl
index ea5f6aef005..01a335af048 100644
--- a/source/blender/gpu/shaders/gpu_shader_basic_frag.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_basic_frag.glsl
@@ -28,8 +28,11 @@
 #define STIPPLE_S3D_INTERLACE_CHECKERBOARD_SWAP        11
 
 #if defined(USE_SOLID_LIGHTING) || defined(USE_SCENE_LIGHTING)
+#if defined(USE_FLAT_NORMAL)
+varying vec3 eyespace_vert_pos;
+#else
 varying vec3 varying_normal;
-
+#endif
 #ifndef USE_SOLID_LIGHTING
 varying vec3 varying_position;
 #endif
@@ -146,7 +149,11 @@ void main()
 
 #if defined(USE_SOLID_LIGHTING) || defined(USE_SCENE_LIGHTING)
 	/* compute normal */
+#if defined(USE_FLAT_NORMAL)
+	vec3 N = normalize(cross(dFdx(eyespace_vert_pos), dFdy(eyespace_vert_pos)));
+#else
 	vec3 N = normalize(varying_normal);
+#endif
 
 #ifdef USE_TWO_SIDED
 	if (!gl_FrontFacing)
diff --git a/source/blender/gpu/shaders/gpu_shader_basic_vert.glsl b/source/blender/gpu/shaders/gpu_shader_basic_vert.glsl
index cef28ea3026..42fbdadf1d1 100644
--- a/source/blender/gpu/shaders/gpu_shader_basic_vert.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_basic_vert.glsl
@@ -1,6 +1,10 @@
 
 #if defined(USE_SOLID_LIGHTING) || defined(USE_SCENE_LIGHTING)
+#if defined(USE_FLAT_NORMAL)
+varying vec3 eyespace_vert_pos;
+#else
 varying vec3 varying_normal;
+#endif
 
 #ifndef USE_SOLID_LIGHTING
 varying vec3 varying_position;
@@ -28,7 +32,13 @@ void main()
 	vec4 co = gl_ModelViewMatrix * gl_Vertex;
 
 #if defined(USE_SOLID_LIGHTING) || defined(USE_SCENE_LIGHTING)
+#if !defined(USE_FLAT_NORMAL)
 	varying_normal = normalize(gl_NormalMatrix * gl_Normal);
+#endif
+#if defined(USE_FLAT_NORMAL)
+	/* transform vertex into eyespace */
+	eyespace_vert_pos = (gl_ModelViewMatrix * gl_Vertex).xyz;
+#endif
 
 #ifndef USE_SOLID_LIGHTING
 	varying_position = co.xyz;