Without knowing exactly which version of Panda you’re using, I can’t tell you precisely what this assertion means, but this is a NodePath assertion, not a collision assertion. I suspect you’re actually getting the error with the line:
map_NP.attach_new_node(map_CNode);Is it possible that map_NP is an empty NodePath? Maybe you meant to do this line instead:
map_NP = NodePath(map_CNode);David