How can I make this 3d model collide with cars? They just go straight through it. I have the blender file and everything...
Yep, depends on the intended use; is it for cutting cars in half or just to drive over/run into. This game uses 2 main categories of actors; vehicles and levels; where vehicles are any dynamic object that is deform-able and movable needs to be JBeamed. More complex to implement, but more possibilities and could be made to cut a car in half, so if that's your goal, you will need this method. Levels on the other hand use statics objects which is a very basic physics model and simple workflow. It stays solid and in place like a slab of concrete and just needs the proper static object hierarchy, before exporting. It can optionally be assigned a collision mesh to lower its CPU impact if it has millions of non-collision related tris. This type of object can't be used as a loadable object in the vehicle selector, so you would need to have a level to feature it in , or mod an oficial level and find a place for it to hang out. https://wiki.beamng.com/Exporting_static_objects