Blender bendy bones and deformation cages for joints
Posted: Fri Oct 05, 2018 9:08 pm
Some time ago Blender added bendy bones, which allow you to bend objects. Here's a simple example where a bendy bone is used to bend a cylinder:
The usual skeleton types cause problems at joints where the surface collapses on the side that gets compressed:
By placing a bendy bone at a joint the collapse can be mitigated. I placed a bendy bone at a knee joint, with one end attached to (parented) the upper leg bone and the other end attached to the lower leg bone. This prevents the collapse:
I suspect that it could be improved further by playing with the placement and weight painting, which I didn't spend much time on. Part of the problem is just the granularity of the mesh, it can be hard to keep a smooth mesh.
Just for illustration, here is the knee joint with the bones displayed as bendy bones. I'm not sure why they get displayed so wide here.
A nice point of this approach is that the animation code isn't affected at all, the bendy bones are controlled by the regular bones without even needing drivers.
Edit:
With slightly less bend the bendy knee isn't distorting at all while the regular knee has already started to collapse:
The usual skeleton types cause problems at joints where the surface collapses on the side that gets compressed:
By placing a bendy bone at a joint the collapse can be mitigated. I placed a bendy bone at a knee joint, with one end attached to (parented) the upper leg bone and the other end attached to the lower leg bone. This prevents the collapse:
I suspect that it could be improved further by playing with the placement and weight painting, which I didn't spend much time on. Part of the problem is just the granularity of the mesh, it can be hard to keep a smooth mesh.
Just for illustration, here is the knee joint with the bones displayed as bendy bones. I'm not sure why they get displayed so wide here.
A nice point of this approach is that the animation code isn't affected at all, the bendy bones are controlled by the regular bones without even needing drivers.
Edit:
With slightly less bend the bendy knee isn't distorting at all while the regular knee has already started to collapse: