Hi,
I'm not too bright about O3D but I may have a few ideas, but not using
the boundingbox.
If you really want to pick a real vertices on a model, try looking at
the 'scattered-chart' example. Even though it is not using O3Dtgz, but
you may get some ideas from it.
If you don't really care about vertices but just any point on the
model, the 'picking' example is good to experiment with it. However,
you might need to deal with world coordinate and local coordinate
transformation if rotating the model is required, but at least I came
out something with it before. Nevertheless, you might be able to pick
the index face ID and position, but not too sure about vertices
location.
If both of these examples doesn't help, sorry about that. I'm also
quite new to 3D programming.
Regards,
Dave