Bone wiggles in simple animation

[h.k.kunchev]

Hi guys,

I have the following problem and hope you can help me. First I wanted to let you know that I have an architecture background and use 3DS max primarily for teaching and doing Architectural Visualizations. I have animated some simple things before but have very little experience in animating with bones. So here´s the problem.

I am trying to make a simple bone animation, that simulates the movement of a robotic arm. For that I created a bone system, that consists of four bones. Then I also added an HI Solver that affects bones number 2, 3 and 4.

After that I started doing the animation, but right at the start I saw that there is some very weird bone wiggling going on. Not every movement I animate causes it, but if you make 4 or 5 movements you definetly see it clearly. I have also added a video in the attachments that illustrates the wiggle problem.

I use 3DS Max 2020.3 on a Windows 10 pro

Thanks for the help and have a nice day!

[leeminardi · Accepted solution]

When moving the goal of an IK Chain there  can be an infinite number of possible configurations for the bones between the root bone and the end bone to which the IK Chain is associated.  For example. place your thumb on a table and keep your shoulder still. You can move your elbow to many different position without moving your thumb or shoulder. An IK solver uses a trial and error approach  to determine the position and rotation of the bones of the IK chain. Several trials are made until a satisfactory solution is found, if one exists.  Take a look at the Preference Settings for Inverse  Kinematics (File, Preferences...).   

In the following example we see that for Interactive IK the mission of the solver is to find a solution where the end position of the bone chain should be within 1.0 units of the IK Chain's goal while the rotation should be within 0.1 degrees.  If that goal is not met within 10 tries then quit.

You could try increasing the number of iterations or make the threshold larger to potentially smooth the interactive action. 

There could be other issues affecting the jerky motion but addressing this is worth a try.

[h.k.kunchev]

Hi Lee,

thanks for the help. Your explanation definetly helped me understand the IK system better. Changing the settings in Preferences did not fix the problem, however I realised, that my threshold was to too high (0.1) and that the IK Chain also has a threshold setting in the command panel settings. I put that to 0.001 and now the wiggle is completely gone.

Many Thanks and have a nice day.