2 files changed, 53 insertions, 5 deletions

diff --git a/intern/cycles/render/nodes.cpp b/intern/cycles/render/nodes.cpp
index 4f54b86fe4a..0304d6d95d1 100644
--- a/intern/cycles/render/nodes.cpp
+++ b/intern/cycles/render/nodes.cpp
@@ -4846,12 +4846,8 @@ void CurvesNode::constant_fold(const ConstantFolder& folder, ShaderInput *value_
 {
 	ShaderInput *fac_in = input("Fac");
 
-	/* remove no-op node */
-	if(!fac_in->link && fac == 0.0f) {
-		folder.bypass(value_in->link);
-	}
 	/* evaluate fully constant node */
-	else if(folder.all_inputs_constant()) {
+	if(folder.all_inputs_constant()) {
 		if (curves.size() == 0)
 			return;
 
@@ -4864,6 +4860,11 @@ void CurvesNode::constant_fold(const ConstantFolder& folder, ShaderInput *value_
 
 		folder.make_constant(interp(value, result, fac));
 	}
+	/* remove no-op node */
+	else if(!fac_in->link && fac == 0.0f) {
+		/* link is not null because otherwise all inputs are constant */
+		folder.bypass(value_in->link);
+	}
 }
 
 void CurvesNode::compile(SVMCompiler& compiler, int type, ShaderInput *value_in, ShaderOutput *value_out)
diff --git a/intern/cycles/test/render_graph_finalize_test.cpp b/intern/cycles/test/render_graph_finalize_test.cpp
index 633e517ce9f..60e41be16aa 100644
--- a/intern/cycles/test/render_graph_finalize_test.cpp
+++ b/intern/cycles/test/render_graph_finalize_test.cpp
@@ -403,6 +403,26 @@ TEST(render_graph, constant_fold_invert_fac_0)
 
 /*
  * Tests:
+ *  - Folding of Invert with zero Fac and constant input.
+ */
+TEST(render_graph, constant_fold_invert_fac_0_const)
+{
+	DEFINE_COMMON_VARIABLES(builder, log);
+
+	EXPECT_ANY_MESSAGE(log);
+	CORRECT_INFO_MESSAGE(log, "Folding Invert::Color to constant (0.2, 0.5, 0.8).");
+
+	builder
+		.add_node(ShaderNodeBuilder<InvertNode>("Invert")
+		          .set("Fac", 0.0f)
+		          .set("Color", make_float3(0.2f, 0.5f, 0.8f)))
+		.output_color("Invert::Color");
+
+	graph.finalize(&scene);
+}
+
+/*
+ * Tests:
  *  - Folding of MixRGB Add with all constant inputs (clamp false).
  */
 TEST(render_graph, constant_fold_mix_add)
@@ -1344,6 +1364,33 @@ TEST(render_graph, constant_fold_rgb_curves_fac_0)
 	graph.finalize(&scene);
 }
 
+
+/*
+ * Tests:
+ *  - Folding of RGB Curves with zero Fac and all constant inputs.
+ */
+TEST(render_graph, constant_fold_rgb_curves_fac_0_const)
+{
+	DEFINE_COMMON_VARIABLES(builder, log);
+
+	EXPECT_ANY_MESSAGE(log);
+	CORRECT_INFO_MESSAGE(log, "Folding Curves::Color to constant (0.3, 0.5, 0.7).");
+
+	array<float3> curve;
+	init_test_curve(curve, make_float3(0.0f, 0.25f, 1.0f), make_float3(1.0f, 0.75f, 0.0f), 257);
+
+	builder
+		.add_node(ShaderNodeBuilder<RGBCurvesNode>("Curves")
+		          .set(&CurvesNode::curves, curve)
+		          .set(&CurvesNode::min_x, 0.1f)
+		          .set(&CurvesNode::max_x, 0.9f)
+		          .set("Fac", 0.0f)
+		          .set("Color", make_float3(0.3f, 0.5f, 0.7f)))
+		.output_color("Curves::Color");
+
+	graph.finalize(&scene);
+}
+
 /*
  * Tests:
  *  - Folding of Vector Curves with all constant inputs.