Im trying to rig a model of a pneumatic muscle, but I can’t find any examples… also I’m pretty much new to rigging, so I would like to ask for some help.
I’m attaching an image of what I want to do for reference. Pneumatic muscle is a thing that is made of bellows in the middle and two metal pads on each side. As the bellows fill with air, the muscle shortens in length and expands on sides.
Modelling this is no problem, but I have no idea what would be the best way to rig this?
I’m guessing I need to somehow scale the bellows in +X and +Y when I scale/move the object in -Z
So, create the object as per the top image of yours. Exit Edit Mode and go to the Vertex Panel - there you will find Shapekeys.
Click “+” button - this will add “Basis” shapekey. Click “+” button again and this will add “Key 1”. Go to Edit Mode.
Check you screen looks like this, select the new “Key 1”:
Icon next the the Pin is greyed out, “Relative” is checked and Value is 0. Change value to 1. Move Vertices to where you want them so it looks like your lower image.
Exit Edit Mode and slide the Value box between 0 and 1. RMB-Click the Value box and chose “Insert Keyframe” at various frames in the timeline to animate it.
You might be able to use a transform constraint to adjust the scale of a deformation bone, I have an example done here (done poorly) to show how to have a muscle expand when another bone is rotated. http://pasteall.org/blend/index.php?id=46089
The first thing that comes to my mind is stretch to bone constraints. Stretch_To preserves volume, and the Volume Variation parameter of the constraint will adjust how much the volume varies.
