Cycles: add folding for redundant A to B to A conversions.

As a result of other folding simplifications it may happen that
two type conversion nodes end up directly connected. In some
cases it may be possible to then remove both. A realistic case
might be an optimized out Mix RGB node used to blend vectors.

It seems it's safe to optimize when B is a float3 type
(color, vector), and A is float3 or float.

Reviewers: #cycles, sergey

Reviewed By: #cycles, sergey

Subscribers: sergey

Differential Revision: https://developer.blender.org/D2134

1 files changed, 68 insertions, 0 deletions

diff --git a/intern/cycles/test/render_graph_finalize_test.cpp b/intern/cycles/test/render_graph_finalize_test.cpp
index cf4083c23db..f84ddc3ff89 100644
--- a/intern/cycles/test/render_graph_finalize_test.cpp
+++ b/intern/cycles/test/render_graph_finalize_test.cpp
@@ -1460,4 +1460,72 @@ TEST(render_graph, constant_fold_rgb_ramp_flat)
 	graph.finalize(&scene);
 }
 
+/*
+ * Tests:
+ *  - Folding of redundant conversion of float to color to float.
+ */
+TEST(render_graph, constant_fold_convert_float_color_float)
+{
+	DEFINE_COMMON_VARIABLES(builder, log);
+
+	EXPECT_ANY_MESSAGE(log);
+	CORRECT_INFO_MESSAGE(log, "Folding Invert::Color to socket convert_float_to_color::value_color.");
+	CORRECT_INFO_MESSAGE(log, "Folding convert_color_to_float::value_float to socket Attribute::Fac.");
+
+	builder
+		.add_attribute("Attribute")
+		.add_node(ShaderNodeBuilder<InvertNode>("Invert")
+		          .set("Fac", 0.0f))
+		.add_connection("Attribute::Fac", "Invert::Color")
+		.output_value("Invert::Color");
+
+	graph.finalize(&scene);
+}
+
+/*
+ * Tests:
+ *  - Folding of redundant conversion of color to vector to color.
+ */
+TEST(render_graph, constant_fold_convert_color_vector_color)
+{
+	DEFINE_COMMON_VARIABLES(builder, log);
+
+	EXPECT_ANY_MESSAGE(log);
+	CORRECT_INFO_MESSAGE(log, "Folding VecAdd::Vector to socket convert_color_to_vector::value_vector.");
+	CORRECT_INFO_MESSAGE(log, "Folding convert_vector_to_color::value_color to socket Attribute::Color.");
+
+	builder
+		.add_attribute("Attribute")
+		.add_node(ShaderNodeBuilder<VectorMathNode>("VecAdd")
+		          .set(&VectorMathNode::type, NODE_VECTOR_MATH_ADD)
+		          .set("Vector2", make_float3(0,0,0)))
+		.add_connection("Attribute::Color", "VecAdd::Vector1")
+		.output_color("VecAdd::Vector");
+
+	graph.finalize(&scene);
+}
+
+/*
+ * Tests:
+ *  - NOT folding conversion of color to float to color.
+ */
+TEST(render_graph, constant_fold_convert_color_float_color)
+{
+	DEFINE_COMMON_VARIABLES(builder, log);
+
+	EXPECT_ANY_MESSAGE(log);
+	CORRECT_INFO_MESSAGE(log, "Folding MathAdd::Value to socket convert_color_to_float::value_float.");
+	INVALID_INFO_MESSAGE(log, "Folding convert_float_to_color::");
+
+	builder
+		.add_attribute("Attribute")
+		.add_node(ShaderNodeBuilder<MathNode>("MathAdd")
+		          .set(&MathNode::type, NODE_MATH_ADD)
+		          .set("Value2", 0.0f))
+		.add_connection("Attribute::Color", "MathAdd::Value1")
+		.output_color("MathAdd::Value");
+
+	graph.finalize(&scene);
+}
+
 CCL_NAMESPACE_END