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, 34 insertions, 8 deletions

diff --git a/intern/cycles/blender/blender_mesh.cpp b/intern/cycles/blender/blender_mesh.cpp
index 4be07ac5e8e..509da1601f3 100644
--- a/intern/cycles/blender/blender_mesh.cpp
+++ b/intern/cycles/blender/blender_mesh.cpp
@@ -285,14 +285,27 @@ static void attr_create_vertex_color(Scene *scene, Mesh *mesh, BL::Mesh &b_mesh,
     BL::Mesh::vertex_colors_iterator l;
 
     for (b_mesh.vertex_colors.begin(l); l != b_mesh.vertex_colors.end(); ++l) {
-      if (!mesh->need_attribute(scene, ustring(l->name().c_str())))
+      const bool active_render = l->active_render();
+      AttributeStandard vcol_std = (active_render) ? ATTR_STD_VERTEX_COLOR : ATTR_STD_NONE;
+      ustring vcol_name = ustring(l->name().c_str());
+
+      const bool need_vcol = mesh->need_attribute(scene, vcol_name) ||
+                           mesh->need_attribute(scene, vcol_std);
+
+      if (!need_vcol) {
         continue;
+      }
 
-      Attribute *attr = mesh->subd_attributes.add(
-          ustring(l->name().c_str()), TypeRGBA, ATTR_ELEMENT_CORNER_BYTE);
+      Attribute *vcol_attr = NULL;
+      if (active_render) {
+        vcol_attr = mesh->subd_attributes.add(vcol_std, vcol_name);
+      }
+      else {
+        vcol_attr = mesh->subd_attributes.add(vcol_name, TypeRGBA, ATTR_ELEMENT_CORNER_BYTE);
+      }
 
       BL::Mesh::polygons_iterator p;
-      uchar4 *cdata = attr->data_uchar4();
+      uchar4 *cdata = vcol_attr->data_uchar4();
 
       for (b_mesh.polygons.begin(p); p != b_mesh.polygons.end(); ++p) {
         int n = p->loop_total();
@@ -307,14 +320,27 @@ static void attr_create_vertex_color(Scene *scene, Mesh *mesh, BL::Mesh &b_mesh,
   else {
     BL::Mesh::vertex_colors_iterator l;
     for (b_mesh.vertex_colors.begin(l); l != b_mesh.vertex_colors.end(); ++l) {
-      if (!mesh->need_attribute(scene, ustring(l->name().c_str())))
+      const bool active_render = l->active_render();
+      AttributeStandard vcol_std = (active_render) ? ATTR_STD_VERTEX_COLOR : ATTR_STD_NONE;
+      ustring vcol_name = ustring(l->name().c_str());
+
+      const bool need_vcol = mesh->need_attribute(scene, vcol_name) ||
+                           mesh->need_attribute(scene, vcol_std);
+
+      if (!need_vcol) {
         continue;
+      }
 
-      Attribute *attr = mesh->attributes.add(
-          ustring(l->name().c_str()), TypeRGBA, ATTR_ELEMENT_CORNER_BYTE);
+      Attribute *vcol_attr = NULL;
+      if (active_render) {
+        vcol_attr = mesh->attributes.add(vcol_std, vcol_name);
+      }
+      else {
+        vcol_attr = mesh->attributes.add(vcol_name, TypeRGBA, ATTR_ELEMENT_CORNER_BYTE);
+      }
 
       BL::Mesh::loop_triangles_iterator t;
-      uchar4 *cdata = attr->data_uchar4();
+      uchar4 *cdata = vcol_attr->data_uchar4();
 
       for (b_mesh.loop_triangles.begin(t); t != b_mesh.loop_triangles.end(); ++t) {
         int3 li = get_int3(t->loops());