Rigid is a green, solid material. It floats just under the surface of Water. Rigid cannot usually be snapped or broken, even with Brittle added. Occasionally, exceptional amounts of force will damage Rigid and cause it to collapse. Rigid can be used to link separate pieces of a creation together and make incredibly complex simulations.
Rigid is one of the most underrated materials in the game. With the discovery of linked particles, Rigid allows the user to make nearly anything you can imagine. Rigid is such a basic material, but it's how you use it that matters.
The only setting that really affects Rigid is standardDistance, because it changes how dense and therefor how strong Rigid behaves.
For some reason, the more dense Rigid is, the less it is able to rotate. Rigid drawn around standardDistance=0.2 has significant trouble rotating at all.