Allow vertex colors to modulate lightmaps.

Weird feature request by artists. Korman's lighting equation selection
looks like it should work fine with this, though. The key is to be sure
that we don't pick up a stale autocolor layer.

korman/exporter/mesh.py

@@ -384,7 +384,7 @@ class MeshConverter(_MeshManager):
 
         # Locate relevant vertex color layers now...
         lm = bo.plasma_modifiers.lightmap
-        color = None if lm.bake_lightmap else self._find_vtx_color_layer(mesh.tessface_vertex_colors)
+        color = self._find_vtx_color_layer(mesh.tessface_vertex_colors, autocolor=not lm.bake_lightmap, manual=True)
         alpha = self._find_vtx_alpha_layer(mesh.tessface_vertex_colors)
 
         # Convert Blender faces into things we can stuff into libHSPlasma
@@ -717,13 +717,15 @@ class MeshConverter(_MeshManager):
             return alpha_layer.data
         return None
 
-    def _find_vtx_color_layer(self, color_collection):
-        manual_layer = next((i for i in color_collection if i.name.lower() in _VERTEX_COLOR_LAYERS), None)
-        if manual_layer is not None:
-            return manual_layer.data
-        baked_layer = color_collection.get("autocolor")
-        if baked_layer is not None:
-            return baked_layer.data
+    def _find_vtx_color_layer(self, color_collection, autocolor: bool = True, manual: bool = True):
+        if manual:
+            manual_layer = next((i for i in color_collection if i.name.lower() in _VERTEX_COLOR_LAYERS), None)
+            if manual_layer is not None:
+                return manual_layer.data
+        if autocolor:
+            baked_layer = color_collection.get("autocolor")
+            if baked_layer is not None:
+                return baked_layer.data
         return None
 
     def is_nonpreshaded(self, bo: bpy.types.Object, bm: bpy.types.Material) -> bool: