This article will take you through the process of creating bones in Autodesk 3ds Max that have scalability, while preserving their volume.These bones will have squash and stretch, ideal for muscles, or exaggerated cartoon-style animation.
Step by step
Most rigs that make use of squishy bones also have a base skeleton made from non-scaling bones. It is easiest if you start out with a simple rig, but it isn't necessary for completing this tutorial.That said, open up 3ds Max (Free 3D Max Models).
Pull down the 'Animation' menu at the top of the window, and then click on 'Bone Tools'.
A dialogue should appear that has several tools for editing bones. Near the top, there is a button called 'Create Bones'. Click it.(Animation menu => Bone Tools => Create Bones)
Left click in the viewport of your choice in a spot where you want your muscle bone to originate. Move your mouse to where the bone should end, and left click again.The tool isn't complete. it's designed to make chains of bones, so it's going to try to make another. Right click anywhere in the viewport to complete the tool.
This should leave you with one reasonably-sized bone, and one tiny nub. Both are necessary for the muscle to be complete.
Name your bones. Select each one individually, and rename it something that will allow you to easily identify it, I'm naming the muscle bone 'Muscle_Bone' and the end bone 'Muscle_Teminator'.
Before you close the 'Bone Tools' dialogue, you need to do one more thing. Select your muscle bone. Now, scroll down to the bottom of the 'Bone Tools' dialogue, and at the very bottom are the stretch options for the bone. make sure that 'Squash' is selected. This will insure that your bone will always scale non-uniformly in a fashion that will preserve volume.
Under the 'Create' tab, in the 'Helpers' subsection, select the 'Dummy' tool. Click and drag in the viewport to create a dummy object, and then create a second one. They should be roughly within the same scale realm as the bones, but slightly larger.(Create => Helpers => Dummy => click in viewport to create) Name your dummy objects, one to indicate that it goes with the muscle, and one to go with the end. These dummy objects will serve as intermediary pieces between your muscle bone and the non-scaling bones in the rest of your rig. I'm naming my dummy objects 'Muscle Dummy' and 'Terminator Dummy'.
Right click on the 'Snaps Toggle' button to bring up the Grid and Snap Settings dialogue. Uncheck everything except 'Pivot'. This is so you can position the dummy objects exactly onto the origins of the bones. Hit 'W' to turn on the move tool, and position each dummy object so that its pivot is directly on its respective bone's pivot point.
I believe order of operations is very important for this part. Believe is the keyword, because anyone who uses software like 3ds Max for any extended period of time will end up very superstitious. Select your muscle bone. Go to the 'Animation' menu, then 'Constraints' submenu, and then 'Position Constraint'. Click on the muscle dummy object. (click bone, Animation => Constraints => Position Constraint, click dummy) Select your end bone, and then apply the same constraint, constraining it to its dummy object.
Select your Muscle bone, and now go to the 'Animation Menu' again, and then to the 'Constraints' menu, and this time select 'LookAt Constraint'. Now click on the end dummy object, NOT the muscle bone dummy. (select muscle bone, Animation => Constraints => LookAt Constraint => click the end dummy).
Your muscle/squishy bone should be ready to use! The easiest way to test it, is to drag one of the dummy objects around, the muscle bone should stretch and squish between the two dummy objects.If you have a rig, all you need to do is link the dummy objects (not the muscle bone or end bone) to the bones you want the squishy bone to be in between.