Eevee: Add small optimisation for Curve Mapping nodes

This remove the RGB texture lookups if the curve is only used for "Luma"
correction and does not affect individual RGB channels.

2 files changed, 50 insertions, 7 deletions

diff --git a/source/blender/gpu/shaders/gpu_shader_material.glsl b/source/blender/gpu/shaders/gpu_shader_material.glsl
index ccc2b7f8ae5..6ce3f6e0cd6 100644
--- a/source/blender/gpu/shaders/gpu_shader_material.glsl
+++ b/source/blender/gpu/shaders/gpu_shader_material.glsl
@@ -525,6 +525,25 @@ void curves_rgb(
 	outcol = mix(col, outcol, fac);
 }
 
+void curves_rgb_opti(
+        float fac, vec4 col, sampler1DArray curvemap, float layer,
+        vec4 range, vec4 ext_a,
+        out vec4 outcol)
+{
+	vec4 co = vec4(RANGE_RESCALE(col.rgb, ext_a.x, range.a), layer);
+	vec3 samp;
+	samp.r = texture(curvemap, co.xw).a;
+	samp.g = texture(curvemap, co.yw).a;
+	samp.b = texture(curvemap, co.zw).a;
+
+	outcol.r = curve_extrapolate(co.x, samp.r, ext_a);
+	outcol.g = curve_extrapolate(co.y, samp.g, ext_a);
+	outcol.b = curve_extrapolate(co.z, samp.b, ext_a);
+	outcol.a = col.a;
+
+	outcol = mix(col, outcol, fac);
+}
+
 void set_value(float val, out float outval)
 {
 	outval = val;
diff --git a/source/blender/nodes/shader/nodes/node_shader_curves.c b/source/blender/nodes/shader/nodes/node_shader_curves.c
index f57d1bfbc9e..2b4c3581fc0 100644
--- a/source/blender/nodes/shader/nodes/node_shader_curves.c
+++ b/source/blender/nodes/shader/nodes/node_shader_curves.c
@@ -115,6 +115,7 @@ static int gpu_shader_curve_rgb(GPUMaterial *mat, bNode *node, bNodeExecData *UN
 {
 	float *array, layer;
 	int size;
+	bool use_opti = true;
 
 	CurveMapping *cumap = node->storage;
 
@@ -139,15 +140,38 @@ static int gpu_shader_curve_rgb(GPUMaterial *mat, bNode *node, bNodeExecData *UN
 			ext_rgba[a][1] = 0.0f;
 			ext_rgba[a][3] = 0.0f;
 		}
+
+		/* Check if rgb comps are just linear. */
+		if (a < 3) {
+			if (range_rgba[a] != 1.0f ||
+			    ext_rgba[a][1] != 1.0f ||
+			    ext_rgba[a][2] != 1.0f ||
+			    cm->totpoint != 2 ||
+			    cm->curve[0].x != 0.0f ||
+			    cm->curve[0].y != 0.0f ||
+			    cm->curve[1].x != 1.0f ||
+			    cm->curve[1].y != 1.0f)
+			{
+				use_opti = false;
+			}
+		}
 	}
 
-	return GPU_stack_link(mat, node, "curves_rgb", in, out, tex,
-	                                               GPU_constant(&layer),
-	                                               GPU_uniform(range_rgba),
-	                                               GPU_uniform(ext_rgba[0]),
-	                                               GPU_uniform(ext_rgba[1]),
-	                                               GPU_uniform(ext_rgba[2]),
-	                                               GPU_uniform(ext_rgba[3]));
+	if (use_opti) {
+		return GPU_stack_link(mat, node, "curves_rgb_opti", in, out, tex,
+		                                                    GPU_constant(&layer),
+		                                                    GPU_uniform(range_rgba),
+		                                                    GPU_uniform(ext_rgba[3]));
+	}
+	else {
+		return GPU_stack_link(mat, node, "curves_rgb", in, out, tex,
+		                                               GPU_constant(&layer),
+		                                               GPU_uniform(range_rgba),
+		                                               GPU_uniform(ext_rgba[0]),
+		                                               GPU_uniform(ext_rgba[1]),
+		                                               GPU_uniform(ext_rgba[2]),
+		                                               GPU_uniform(ext_rgba[3]));
+	}
 }
 
 void register_node_type_sh_curve_rgb(void)