Making Dynamic Capes

General / 16 April 2019

On this post, I wanted to go over how to make a cape that switches between FK joints and dynamic joints.

Rigs that need to be imported into an engine are usually joint-based, meaning that using software like nCloth won't work in a game.

By putting the nCloth through the joints and in turn the mesh, we can have the behavior of dynamic cloth and not lose any information when imported in-engine.

First, I started out with 3 joint chains going down the cape.

I then made a NURBS curve that runs down each of the chains.  

I duplicated those curves, making 3 for each curve. So 9 in total.

I ran a simple IK spline handle through each of the chains using the curves made previously. 

The two other curves per each chain were designated to the FK control curve and the Dynamic curve.

To make the FK controls I used clusters on the FK control curve CVs.

I placed controls on that for movement.

After making controls for the FK curve, I went ahead and started on making the dynamic cape work.

I created a plane that I can run a nCloth simulation through the cape. The cloth was created by duplicating and offsetting the dynamic curve in the center, lofting, and then converting them into polygons. 

After turning the polygon to a nCloth, I lofted the 3 dynamic curves onto the cloth. Now the dynamic curve follows the cloth!

After setting up the spline curve, the FK curve, and the dynamic curve, I then used blendshapes to move between the two curves.

Using the node editor and the attribute editor, I was able to make a system that can switch between FK and dynamic controls.

After the rig was working, there were still problems to fix. The major problem with relying on multiple IK splines is that they double transform, and send the cape flying away from the model.

Using some unorthodox methods I barely managed to get the switching to work with the model. I used a combination of parenting, turning off "enable transforms", and node editor switching, etc.

It may be a bug on Maya's side, but whenever the file is opened you have to wiggle the cape controls around from FK to dynamic for it to correctly work.    

Using a very similar technique on the ponytail, I also got a dynamic system to work there as well!

Thanks for reading!