topic Position of bones and IK solvers for 4bar system in 3ds Max Animation and Rigging Forum

Position of bones and IK solvers for 4bar system

Anonymous — Tue, 08 Sep 2020 17:36:54 GMT

Hi guys,

I am a mechnical student, and I was always using Solidworks to do mechinical modeling and simulation. This time I need to use 3ds max to achieve some compliant modeling, but I am totally new for this. The version of 3ds max is 2020. I tried to import the whole assembly file from solidworks to 3ds, but I realized that it lost all the mates I did, and the whole structure became rigid. Then I import the file piece by piece, and tried to build bones and IK solvers like others did, but I am coonfused about the positions of them..

The question I have right now are:

1. Is it ok if I imported directly the solidworks file to make a animation in 3ds max?

2. Where should I add bones and IK solvers in this 4-bar linkage system?

This structure is aimed to be move like this:

And Here is my max. file. I basically just finished importing the files, and place them correctly.

Any help will be sincerely appreciately!

Best,

Jacky

Re: Position of bones and IK solvers for 4bar system

leeminardi — Tue, 08 Sep 2020 19:10:09 GMT

I took a quick look at your model. A few comments,

Label your geometry in a concise logical scheme. E.g., link1, link2,... fish1, fist2,...
Make sure all the pivots have a z coordinate of 0.0. IK solvers work on a 2D plane and you want to make sure the plane is the XY, z = 0 for this rig.
Ungroup and unlink everything.
Reset the transform for all geometry.
Place the pivots in a logical position for each of the links that define you basic 4-bar linkage. In the figure below I've noted the position of the pivots for the 3 links that compose the 4-bar linkage (the 4th link is ground, your red link, which does not move).
I usually find it best to not have two links straight inline when creating the IK solver so rotate the links a bit to start.
Link a dummy to link 2 then add the HI IK Solver from 1 to the dummy.
Link the goal of the IK SOlver to link 3.
Since your geometry is relatively small (most dimensions are less than 1) you should decrease the value of the thresholds position tolerance accordingly. Tjis is the value the numerical solver uses to determine when it has reached an acceptable solution. I found 0.001 gave smooth interactive results.
Get one 4-bar "cell" working well then you can clone it and reposition it for the other cells.
When the chain is complete I think you can add another HI IK Solver from the base link of the first 4-bar to the ed link of the last 4-bar.

Good luck!

Re: Position of bones and IK solvers for 4bar system

Anonymous — Tue, 08 Sep 2020 19:49:51 GMT

Hi Lee,

Thanks for these helpful advice! I appreciate so much that you can check my file and guide me in details!

I'll try to fix all you said, and I will get back to you. Thank you!