I'm interested in having a triangle mesh "filter" object where other objects can pass through its surface from one direction but collide with it from the other direction. I am pretty sure my answer lies somewhere with collision groups, contact callbacks, and/or the btInternalEdgeUtility, though my experience with these is very limited. Perhaps I could use a callback to check the collision normal and, if an object is approaching the filter from a certain side, somehow make it ignore the collision (not sure how) and pass through, whereas if the object is colliding from the other side, let it collide as normal?
Any suggestions are appreciated.