IK Animation troubles

I’m having a lot of trouble doing some simple IK animation. The file below is just a piece of a much larger set of moving lines/components. I want to work the bugs out one little piece at a time.

The heirarchy looks like this:

A

B
C
D

A is a simple constraint to Path 1
B is a joint (hinge - Y)
C (the circle) is a joint (Hinge - Y) and constraint to point D
D is a constraint to Path 2

In the future more than one object will be constrained to point D which is why it is set up this way. When I view the animation, point D follows the line mostly, but says “Bongo Constraint: goal not reached”. Why am I getting this error?

Simple animation problem.3dm (160.5 KB)

The message board screwed up the heirarchy formatting. Basically A is the parent, then child B then B’s child C, then C’s child D.

Travis,

First, in order to make the hinges work in the correct direction, you need to rotate them so that they line up with the lines.

Second, you have now 2 constraints in the IK chain, you should only have one constrain goal. Why not have C as the goal(constrain) and D as a child of the goal, so that you then can hook up other or remove the constrain from C and only have D as the constrain.

Third, the reason why Bongo can’t solve the animation is because it needs more movement in the pivot in order to solve it. With only Hinge movement in the Y axis, the result is like this seen from above at the end:

If you change the joint moment to Universal and allow movement along the x and the y axis, Bongo can solve the animation for you.

Please see example.Simple animation problem 001.3dm (158.7 KB)

Bringing this back to the top. I don’t understand what you mean by have C as the goal. How do I accomplish this?

I’ve rotated this to be in the correct plane and the Y axis in the correct orientation. I’ve set it up again like I did earlier, but it still does not work. I don’t understand the proper way to set this up.Simple animation problem 002.3dm (171.2 KB)

Travis,

You seem to have one goal to much. The way you have it set up now makes it impossible to solve.

The easiest way to get your model to work is to remove one of the goals (Object 2), and make the Rails Slide Point a child of Object 2. Rails Slide Point will then be the goal if the IK chain. Please see attached model.
Simple animation problem 002_1.3dm (174.0 KB)

Thank you. I suppose I understand that. I’m still having a lot of trouble with parallelogram type setups - is there a way I can submit a file to you or the bongo team directly for support that I don’t wish to share publicly on this forum?

-Travis

Depending on the size you can send the file directly to my email at marika.almgren@mcneel.com or upload it to me using the McNeel upload site:
http://www.rhino3d.com/upload