Major Design Overhaul

[Windcatcher]

The likely reason you can walk through a bag is because it probably isn't checked in the collision-checking code. The same is for tree leaves; all that's needed is a flag for checking/not checking collisions. As long as an object is placed appropriately in the BSP tree/octree, it can be checked for the purpose of collision avoidance. The only issue is polygon count: adding too many polygons in a small area can cause lag.