The cause of camera movement being blocked (in area models) does technically come from the walkmesh but here is the plot twist; it comes from the walkmesh node INSIDE the .mdl file. It specifically comes from the AABB tree. You can see for yourself: Find a area model in a selected module, remove the AABB tree (have to replace the first AABB with a AABB assigned to a face, otherwise it crashes), then add the .mdl to the override, proceed to load the module and pan the camera through the walls - just make sure you are in the right model of the module. Now we just need to put this information to good use...