The cave items are to far off the terrain for AI to walk in them even with the forcesimplecollision = 3. For AI to walk in these kinds of objects the floor must be no higher then 5cm thick.
These cave parts are not intended with walking AI at the moment. Once the capability to walk on objects thicker then that, then these should work also.
As far as the order things get done in programming, it boils down to what can be added and completed, with out disabling the functionality that is there. In the effort to make this an easy game making experience, it also must be simple and almost one button to accomplish. This is the hard part. Making it transparent and simple.
AI requires to know where they are in 3d space at all times, making it difficult to let them do there thing. Yes this could be done right now, but at the expense of you having to draw or trace the intended objects that you want them to walk on. Not for every one and certainly not easy.
This product is still in Beta even thou out of early access and new functions and completed functions will continue to be made for years to come.
Hope that clarifies some questions.
Thank you.
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