Fix T73938: Cycles Vertex Color wrong if no layer is specified

The node would render black in this case (but should use the
'active_render' layer choosen in the object data properties -- this is
now in line to how this is handled for e.g. UVs)

This introduces ATTR_STD_VERTEX_COLOR and uses this thoughout, if no
particular layer is specified in the node.

Maniphest Tasks: T73938

Differential Revision: https://developer.blender.org/D6887

1 files changed, 10 insertions, 1 deletions

diff --git a/intern/cycles/kernel/shaders/node_vertex_color.osl b/intern/cycles/kernel/shaders/node_vertex_color.osl
index 70843b5543a..ffaf7a2f720 100644
--- a/intern/cycles/kernel/shaders/node_vertex_color.osl
+++ b/intern/cycles/kernel/shaders/node_vertex_color.osl
@@ -22,7 +22,16 @@ shader node_vertex_color(string bump_offset = "center",
                          output float Alpha = 0.0)
 {
   float vertex_color[4];
-  if (getattribute(layer_name, vertex_color)) {
+  string vertex_color_layer;
+
+  if (layer_name == "") {
+    vertex_color_layer = "geom:vertex_color";
+  }
+  else {
+    vertex_color_layer = layer_name;
+  }
+
+  if (getattribute(vertex_color_layer, vertex_color)) {
     Color = color(vertex_color[0], vertex_color[1], vertex_color[2]);
     Alpha = vertex_color[3];