Node: Mix node

This patch is a response to T92588 and is implemented
as a Function/Shader node.

This node has support for Float, Vector and Color data types.

For Vector it supports uniform and non-uniform mixing.

For Color it now has the option to remove factor clamping.

It replaces the Mix RGB for Shader and Geometry node trees.

As discussed in T96219, this patch converts existing nodes
in .blend files. The old node is still available in the
Python API but hidden from the menus.

Reviewed By: HooglyBoogly, JacquesLucke, simonthommes, brecht

Maniphest Tasks: T92588

Differential Revision: https://developer.blender.org/D13749

1 files changed, 95 insertions, 0 deletions

diff --git a/intern/cycles/scene/constant_fold.cpp b/intern/cycles/scene/constant_fold.cpp
index 4bce5661f9b..1aa4515a087 100644
--- a/intern/cycles/scene/constant_fold.cpp
+++ b/intern/cycles/scene/constant_fold.cpp
@@ -291,6 +291,101 @@ void ConstantFolder::fold_mix(NodeMix type, bool clamp) const
   }
 }
 
+void ConstantFolder::fold_mix_color(NodeMix type, bool clamp_factor, bool clamp) const
+{
+  ShaderInput *fac_in = node->input("Factor");
+  ShaderInput *color1_in = node->input("A");
+  ShaderInput *color2_in = node->input("B");
+
+  float fac = clamp_factor ? saturatef(node->get_float(fac_in->socket_type)) :
+                             node->get_float(fac_in->socket_type);
+  bool fac_is_zero = !fac_in->link && fac == 0.0f;
+  bool fac_is_one = !fac_in->link && fac == 1.0f;
+
+  /* remove no-op node when factor is 0.0 */
+  if (fac_is_zero) {
+    /* note that some of the modes will clamp out of bounds values even without use_clamp */
+    if (!(type == NODE_MIX_LIGHT || type == NODE_MIX_DODGE || type == NODE_MIX_BURN)) {
+      if (try_bypass_or_make_constant(color1_in, clamp)) {
+        return;
+      }
+    }
+  }
+
+  switch (type) {
+    case NODE_MIX_BLEND:
+      /* remove useless mix colors nodes */
+      if (color1_in->link && color2_in->link) {
+        if (color1_in->link == color2_in->link) {
+          try_bypass_or_make_constant(color1_in, clamp);
+          break;
+        }
+      }
+      else if (!color1_in->link && !color2_in->link) {
+        float3 color1 = node->get_float3(color1_in->socket_type);
+        float3 color2 = node->get_float3(color2_in->socket_type);
+        if (color1 == color2) {
+          try_bypass_or_make_constant(color1_in, clamp);
+          break;
+        }
+      }
+      /* remove no-op mix color node when factor is 1.0 */
+      if (fac_is_one) {
+        try_bypass_or_make_constant(color2_in, clamp);
+        break;
+      }
+      break;
+    case NODE_MIX_ADD:
+      /* 0 + X (fac 1) == X */
+      if (is_zero(color1_in) && fac_is_one) {
+        try_bypass_or_make_constant(color2_in, clamp);
+      }
+      /* X + 0 (fac ?) == X */
+      else if (is_zero(color2_in)) {
+        try_bypass_or_make_constant(color1_in, clamp);
+      }
+      break;
+    case NODE_MIX_SUB:
+      /* X - 0 (fac ?) == X */
+      if (is_zero(color2_in)) {
+        try_bypass_or_make_constant(color1_in, clamp);
+      }
+      /* X - X (fac 1) == 0 */
+      else if (color1_in->link && color1_in->link == color2_in->link && fac_is_one) {
+        make_zero();
+      }
+      break;
+    case NODE_MIX_MUL:
+      /* X * 1 (fac ?) == X, 1 * X (fac 1) == X */
+      if (is_one(color1_in) && fac_is_one) {
+        try_bypass_or_make_constant(color2_in, clamp);
+      }
+      else if (is_one(color2_in)) {
+        try_bypass_or_make_constant(color1_in, clamp);
+      }
+      /* 0 * ? (fac ?) == 0, ? * 0 (fac 1) == 0 */
+      else if (is_zero(color1_in)) {
+        make_zero();
+      }
+      else if (is_zero(color2_in) && fac_is_one) {
+        make_zero();
+      }
+      break;
+    case NODE_MIX_DIV:
+      /* X / 1 (fac ?) == X */
+      if (is_one(color2_in)) {
+        try_bypass_or_make_constant(color1_in, clamp);
+      }
+      /* 0 / ? (fac ?) == 0 */
+      else if (is_zero(color1_in)) {
+        make_zero();
+      }
+      break;
+    default:
+      break;
+  }
+}
+
 void ConstantFolder::fold_math(NodeMathType type) const
 {
   ShaderInput *value1_in = node->input("Value1");