VC limit reached warning

Some bake modes use internally a custom Vertex Color layer which is removed once the bake finishes. If the maximum number of VC layers are in use in an object to be baked from (that is, 8), warn about it and gray out the Bake button to avoid an exception.

Additionally, make sure materials without node tree don't make the addon UI refresh fail in the search of UDIMs, writing an error in the Console..

__init__.py

@@ -836,11 +836,13 @@ def get_UDIM_image():
 						for i in range(len(obj.material_slots)):
 							slot = obj.material_slots[i]
 							if slot.material:
-								nodes = slot.material.node_tree.nodes
-								if nodes:
-									for node in nodes:
-										if node.type == 'TEX_IMAGE' and node.image and node.image.source =='TILED':
-											return node.image
+								tree = slot.material.node_tree
+								if tree:
+									nodes = tree.nodes
+									if nodes:
+										for node in nodes:
+											if node.type == 'TEX_IMAGE' and node.image and node.image.source =='TILED':
+												return node.image
 						return None
 
 					if bpy.context.scene.texToolsSettings.UDIMs_source == 'OBJECT':

op_bake.py

@@ -87,7 +87,7 @@ def poll(cls, context):
 			settings.bake_error = ""
 			return True
 
-		if modes[bake_mode].material == "":
+		if modes[bake_mode].setVColor or not modes[bake_mode].material:
 			def is_bakeable(obj):
 				if len(obj.data.materials) <= 0:	# There are no material slots
 					settings.bake_error = "Materials needed"
@@ -113,16 +113,33 @@ def is_bakeable(obj):
 						# 	return False
 				settings.bake_error = ""
 				return True
-
+
+			def is_vc_ready(obj):
+				if len(obj.data.vertex_colors) > 7:
+					settings.bake_error = "An empty VC layer needed"
+					return False
+				settings.bake_error = ""
+				return True
+
 			for bset in settings.sets:
 				if (len(bset.objects_high) + len(bset.objects_float)) == 0:
-					for obj in bset.objects_low:
-						if not is_bakeable(obj):
-							return False
+					if not modes[bake_mode].material:
+						for obj in bset.objects_low:
+							if not is_bakeable(obj):
+								return False
+					if modes[bake_mode].setVColor:
+						for obj in bset.objects_low:
+							if not is_vc_ready(obj):
+								return False
 				else:
-					for obj in (bset.objects_high+bset.objects_float):
-						if not is_bakeable(obj):
-							return False
+					if not modes[bake_mode].material:
+						for obj in (bset.objects_high + bset.objects_float):
+							if not is_bakeable(obj):
+								return False
+					if modes[bake_mode].setVColor:
+						for obj in (bset.objects_high + bset.objects_float):
+							if not is_vc_ready(obj):
+								return False
 
 		settings.bake_error = ""
 		return True