[Bf-blender-cvs] [55e3c17ccc1] blender2.8: Edit Mesh: Optimize the overlay triangle geometry shader

[Clément Foucault]

Commit: 55e3c17ccc1e6154db69d0143edd9457c6948c8d
Author: Clément Foucault
Date:   Sat Oct 13 23:43:33 2018 +0200
Branches: blender2.8
https://developer.blender.org/rB55e3c17ccc1e6154db69d0143edd9457c6948c8d

Edit Mesh: Optimize the overlay triangle geometry shader

On my test it's 30% faster than before.

Test case : Suzanne, subsurf lvl3, 64K tris, Edge select mode for fair
comparison.

0.95ms before optimization
0.64ms after optimization

Note that this only optimize the "nicest" display of edit mesh overlays,
not the one when rotating the view where half of the border edges are
missing.

===================================================================

M	source/blender/draw/modes/shaders/edit_mesh_overlay_geom_tri.glsl

===================================================================

diff --git a/source/blender/draw/modes/shaders/edit_mesh_overlay_geom_tri.glsl b/source/blender/draw/modes/shaders/edit_mesh_overlay_geom_tri.glsl
index 9b57e450688..61f3e818020 100644
--- a/source/blender/draw/modes/shaders/edit_mesh_overlay_geom_tri.glsl
+++ b/source/blender/draw/modes/shaders/edit_mesh_overlay_geom_tri.glsl
@@ -9,7 +9,7 @@ layout(triangles) in;
  * triangle. Order is important.
  * TODO diagram
  */
-layout(triangle_strip, max_vertices=15) out;
+layout(triangle_strip, max_vertices=12) out;
 
 uniform mat4 ProjectionMatrix;
 uniform vec2 viewportSize;
@@ -36,6 +36,12 @@ out vec3 vertexColor;
 out float facing;
 #endif
 
+#ifdef ANTI_ALIASING
+#define Z_OFFSET 0.008
+#else
+#define Z_OFFSET 0.0
+#endif
+
 /* project to screen space */
 vec2 proj(vec4 pos)
 {
@@ -56,20 +62,33 @@ void doVertex(int v)
 	EmitVertex();
 }
 
-void doLoopStrip(int v, vec3 offset)
+void doVertexOfs(int v, vec2 fixvec)
 {
-	doVertex(v);
+#ifdef VERTEX_SELECTION
+	vertexColor = EDIT_MESH_vertex_color(vData[v].x).rgb;
+#endif
 
-	gl_Position.xyz += offset;
+#ifdef VERTEX_FACING
+	facing = vFacing[v];
+#endif
+	gl_Position = pPos[v];
+
+	gl_Position.xyz += vec3(fixvec, Z_OFFSET);
 
 	EmitVertex();
 }
 
-#ifdef ANTI_ALIASING
-#define Z_OFFSET 0.008
-#else
-#define Z_OFFSET 0.0
-#endif
+void mask_edge_flag(int v, ivec3 eflag)
+{
+	int vbe = (v + 2) % 3;
+	int vaf = (v + 1) % 3;
+
+	/* Only shade the edge that we are currently drawing.
+	 * (fix corner bleeding) */
+	flag[vbe] |= (EDGE_EXISTS & eflag[vbe]);
+	flag[vaf] &= ~EDGE_EXISTS;
+	flag[v]   &= ~EDGE_EXISTS;
+}
 
 void main()
 {
@@ -82,32 +101,23 @@ void main()
 	}
 
 	/* Face */
+	vec4 fcol;
 	if ((vData[0].x & FACE_ACTIVE) != 0)
-		faceColor = colorFaceSelect;
+		fcol = colorFaceSelect;
 	else if ((vData[0].x & FACE_SELECTED) != 0)
-		faceColor = colorFaceSelect;
+		fcol = colorFaceSelect;
 	else if ((vData[0].x & FACE_FREESTYLE) != 0)
-		faceColor = colorFaceFreestyle;
+		fcol = colorFaceFreestyle;
 	else
-		faceColor = colorFace;
+		fcol = colorFace;
 
 	/* Vertex */
 	ssPos[0] = proj(pPos[0]);
 	ssPos[1] = proj(pPos[1]);
 	ssPos[2] = proj(pPos[2]);
 
-	doVertex(0);
-	doVertex(1);
-	doVertex(2);
-
-	EndPrimitive();
-
-	for (int v = 0; v < 3; ++v) {
-		flag[v] &= ~EDGE_VERTEX_EXISTS;
-	}
-
-	vec2 fixvec[6];
-	vec2 fixvecaf[6];
+	vec2 fixvec[3];
+	vec2 fixvecaf[3];
 
 	/* This fix the case when 2 vertices are perfectly aligned
 	 * and corner vectors have nowhere to go.
@@ -152,26 +162,31 @@ void main()
 		}
 	}
 
-	/* to not let face color bleed */
-	faceColor.a = 0.0;
-
-	/* Start with the same last vertex to create a
-	 * degenerate triangle in order to "create"
-	 * a new triangle strip */
-	for (int i = 2; i < 5; ++i) {
-		int vbe = (i - 1) % 3;
-		int vaf = (i + 1) % 3;
-		int v = i % 3;
+	/* Remember that we are assuming the last vertex
+	 * of a triangle is the provoking vertex (decide what flat attribs are). */
 
-		doLoopStrip(v, vec3(fixvec[v], Z_OFFSET));
-
-		/* Only shade the edge that we are currently drawing.
-		 * (fix corner bleeding) */
-		flag[vbe] |= (EDGE_EXISTS & eflag[vbe]);
-		flag[vaf] &= ~EDGE_EXISTS;
-		flag[v]   &= ~EDGE_EXISTS;
-		doLoopStrip(vaf, vec3(fixvecaf[v], Z_OFFSET));
-
-		EndPrimitive();
-	}
+	/* Do 0 -> 1 edge strip */
+	faceColor = vec4(fcol.rgb, 0.0);
+	mask_edge_flag(0, eflag);
+	doVertexOfs(0, fixvec[0]);
+	doVertexOfs(1, fixvecaf[0]);
+	doVertex(0);
+	doVertex(1);
+	/* Do face triangle */
+	faceColor = fcol;
+	flag = eflag;
+	doVertex(2);
+	faceColor.a = 0.0; /* to not let face color bleed */
+	/* Do 1 -> 2 edge strip */
+	mask_edge_flag(1, eflag);
+	doVertexOfs(1, fixvec[1]);
+	doVertexOfs(2, fixvecaf[1]);
+	EndPrimitive();
+	/* Do 2 -> 0 edge strip */
+	mask_edge_flag(2, eflag);
+	doVertex(2);
+	doVertex(0);
+	doVertexOfs(2, fixvec[2]);
+	doVertexOfs(0, fixvecaf[2]);
+	EndPrimitive();
 }