Object Mode Engine: Optimize outline passes.

Group texture fetches to hide latency. 3.2ms -> 2.2ms (constant time improvement, not depending on scene complexity)

Could optimize further with textureGather (require OpenGL 4.0).

1 files changed, 18 insertions, 25 deletions

diff --git a/source/blender/draw/modes/shaders/object_outline_expand_frag.glsl b/source/blender/draw/modes/shaders/object_outline_expand_frag.glsl
index e0568d1157a..c753e3ab39c 100644
--- a/source/blender/draw/modes/shaders/object_outline_expand_frag.glsl
+++ b/source/blender/draw/modes/shaders/object_outline_expand_frag.glsl
@@ -9,37 +9,30 @@ uniform sampler2D outlineDepth;
 uniform float alpha;
 uniform bool doExpand;
 
-void search_outline(ivec2 uv, inout bool found_edge)
-{
-	if (!found_edge) {
-		vec4 color = texelFetch(outlineColor, uv, 0).rgba;
-		if (color.a != 0.0) {
-			if (doExpand || color.a != 1.0) {
-				FragColor = color;
-				found_edge = true;
-			}
-		}
-	}
-}
-
 void main()
 {
 	ivec2 uv = ivec2(gl_FragCoord.xy);
 	FragColor = texelFetch(outlineColor, uv, 0).rgba;
 	float depth = texelFetch(outlineDepth, uv, 0).r;
 
-	if (FragColor.a != 0.0 || (depth == 1.0 && !doExpand))
-		return;
+	vec4 color[4];
+	color[0] = texelFetchOffset(outlineColor, uv, 0, ivec2( 1,  0)).rgba;
+	color[1] = texelFetchOffset(outlineColor, uv, 0, ivec2( 0,  1)).rgba;
+	color[2] = texelFetchOffset(outlineColor, uv, 0, ivec2(-1,  0)).rgba;
+	color[3] = texelFetchOffset(outlineColor, uv, 0, ivec2( 0, -1)).rgba;
+
+	vec4 values = vec4(color[0].a, color[1].a, color[2].a, color[3].a);
+
+	bool is_blank_pixel = !(FragColor.a != 0.0 || (depth == 1.0 && !doExpand));
+	vec4 tests = vec4(is_blank_pixel);
+	tests *= step(vec4(1e-6), values); /* (color.a != 0.0) */
+	tests *= (doExpand) ? vec4(1.0) : step(values, vec4(0.999)); /* (doExpand || color.a != 1.0) */
+	bvec4 btests = equal(tests, vec4(1.0));
 
-	bool found_edge = false;
-	search_outline(uv + ivec2( 1,  0), found_edge);
-	search_outline(uv + ivec2( 0,  1), found_edge);
-	search_outline(uv + ivec2(-1,  0), found_edge);
-	search_outline(uv + ivec2( 0, -1), found_edge);
+	FragColor = (btests.x) ? color[0] : FragColor;
+	FragColor = (btests.y) ? color[1] : FragColor;
+	FragColor = (btests.z) ? color[2] : FragColor;
+	FragColor = (btests.w) ? color[3] : FragColor;
 
-	/* We Hit something ! */
-	if (found_edge) {
-		/* only change alpha */
-		FragColor.a *= alpha;
-	}
+	FragColor *= (is_blank_pixel) ? alpha : 1.0;
 }