How to simulate multiple legs moving

Dear Experts,
I used the same structure in these two legs, but they worked differently. The one worked with no problem, but the other have a problem. I am confused. Hope you can give me some advice.Thank you.

spider theory.3dm (74.4 KB)


The one leg is malfunctioning because the Hinges (and likewise the pivots) are not orientated parallel to the World directions. In Bongo’s Object Properties there is an option “Rotate in world space’ which is by default enabled.
This makes an object rotate according to the Wolrd’s directions no matter how the pivot is oriented. When you disable the option the Hinges will operate as you expect.

I noticed you had some trouble with the use of an IK-constrain to an object. Allow me some tutoring.
Object 10 is constraint to noting. It was probably constraint to some object that you later deleted. Although the IK of the leg appears to function properly, this is only fortunate but not the way it should be done.
Object 14 is constrained to its own child (Object 22). This neither makes any sense.
What you need is (for both objects) the “Keep pivot location, orientation and scaling” option. This absolutely immobilizes the object.
But when you want the last part of the legs (objects 10 and 14) to hinge around the point objects 19 and 22, other measures must be taken.


PS Via the monitor I also noticed that the hinges of Objects 20, 21 and 14 are not perfectly in line (Z should be 60° for all of them).
Fortunately for you, the default IK tolerance can cope with it. I don’t know which technique you use to for the orientation, but here is a tip for the other legs: simply use Rhino’s Rotate command with the Copy option enabled to make a copy of the first leg in the ZX plane (Object 8, 9 and 10). The pivots rotate along nicely.