Cartoon Muscle Animation

by Stefan Andersson


Muscle animation can be easy. What you can do is animate a shape and use the "link with" command. My example is almost like the tutorial that can be found on Softimage.com but a little bit different. It doesn't work for all kinds of muscular animation but for simple animation on cartoony characters it'll work fine (which is most of my work).

First we'll start off my character Bernie.



Bernie's arm is a tiny cartoon arm with not so much of bulging muscles. So what I'll do is modify it with just a tiny little bit of movment.

Part 1.

I belive you all know how to envelope so I'll skip that part. However, if you don't know you should take a closer look at the tutorial book that comes with XSI :)

I select my left arm and then i TAG all points on the arm, OR you could only select the biceps vertex points which would be a more intelligent suggestion (I'm not always smart... hehe).



I then save the hole arm as a shape key (Biceps for you).




Then I rotate my arm in to a bend position. I then modify the mesh to have a more bulgeing look. After that I select all the points again (again biceps for you).


Now this is important, move one frame forward and then save another shape key. You now have to shape keys which we are going to use in the Animation Mixer. So straighten out the arm, select the arm mesh again and then go into the Animation Mixer. Press the button update so that you'll see the shape tracks. Select the shape animation on the shape track and delete it. We don't need the animation made by XSI. But we still have the shapes stored in the mixer.



If you right click on the first shape track and go to Load Source you will see two shapes stored.



So select the first shape (which should be the "normal" shape) and place it on the first shape track. Then drag it out to so that it covers the hole animation.



Then do the same thing for the next shape on the second shape track.



We now want to link the sliders with the rotation of the bone. Now is a good time to name your skeleton parts if you haven't done that before. For this example I only named my forearm (yes I'm lazy). On the first shape track (the normal) right click on the keyframe button (the green one) and select link with.



Then I find my Left_Forearm - Kinematics - Local Transform - Ori - Euler - Y. When you click on 'Y' the popup disapears. And you'll see that the green button has changed. You now have linked the shape the the Y rotation of your Forearm. But we need to set a "relative value" (you'll understand what this is when we do it). If you now right click on the keyframe button you can chose copy animation. Then right click on the second shape track and do Paste Animation. That was soooo easy.. right?

Make sure your arm is in relaxed position.



Drag the first shape track slider to '1' and the second one to '0'. Right click on the keyframe button of the first track and select Set relative value (on both tracks).



Now rotate the arm into a bend position.



Drag the first shape track slider to '0' and the second one to '1'. Right click on the keyframe button of the first track and select Set relative value (on both tracks). If you now rotate your arm back and forth you'll see how the biceps shape is changing.



I hope you enjoyed it and that amazing animation will florish :) This might not be the best example in the world, but I hope it gave you some other ideas.


Stefan Andersson
Character Animator
Filmtecknarna F. Animation