Hi folks. I’ve run into a little glitch in rigid body mechanics using the game engine. Here’s what I’m trying to do:
I’ve set myself the challenge of creating a steam powered prosthetic hand in Blender.
I’m using rigid bodies to model the motion of various component parts of the structure so that the final modelling will be accurate and functionally correct.
What I have so far is a rigid body structure representing a finger joint consisting of a mechanical linkage powered by a piston. There are brass plates attached to the outside of the finger to which the linkage chain is attached. It’s working up to a point, but there seems to be a glitch in the motion of the piston. As it extends, the piston arm bends in relation to the cylinder. I’m wondering if anyone has any hints about how to minimise/remove this glitch.
I’ve tried using the “Track to” and “Child of” constraints, but these don’t seem to be supported in the game engine. The solution I’m working with involves 6DOF rigid body joints to limit the motion of the piston arm to the piston cylinder.
Any hints/tips would be appreciated.
Finger_linkage_sketch.blend (46 KB)
The model structure in the .blend is pretty messy since I’m just playing with ideas right now, but the finger linkage is gravity driven and can be seen if you open the .blend and press P. The glitch between the piston cylinder and arm can be easily seen. It bends then straightens again.
The messy structure is possibly contributing to this glitch, but I think it is unlikely to be the sole cause. If I’ve missed some kind of restraint that would help then please let me know, or If I’m not using the rigid body joint constraints right then please lend me some words of advice.
Thanks for reading.
Edit: Updated the file to better represent the issue. All action is animated via a rotation ipo on a single empty. The glitch can be seen again and again as the joint bends and straightens.
Edit2: Fixed it.
Finger_linkage_sketch-1.blend (178 KB)
For anyone who’s interested, I just needed to move the pivot point of the 6DOF constraint on the piston arm to the back of the piston cylinder. Check out the revised file, I’m pretty impressed with the rigid body functionality of the game engine.