Turn on Collision, but still can go through
 

This is a weird thing. I turn on the collision using viz.collision(viz.ON), and all of the objects inside the boundary are impenetrable. But the problem occurs on the boundary. When I go really hard to the wall, sometimes I can go through!?

Does anybody have this experience? I use google sketchup to make the objects.

How are controlling the viewpoint movements? Does the viewpoint go through when using the standard mouse navigation with default speed?

Thank you for your prompt reply!

Yes. I use vizcam.KeyboardCamera with default speed and viz.WalkNavigate, and both of them would go out of the boundary if I keep hitting the wall.

I also implement the joystick version, same result. But I have to emphasize that it only happens when you try to hit the wall for more than 1 second.

Do you still have this issue if you export the model with the Export Two-Sided Faces option enabled?

Oh, you are a genius. Thanks!