Download Obi Softbody FREE Unity.
Obi Softbody is a high-quality, high-performance soft-body physics engine based on cutting-edge technology. Simulate complex elastoplastic soft bodies composed of thousands of polygons, complete with collisions, self-collision and rigid body interaction.
Disclaimer: this is not a clay/mesh sculpting tool, and is not suitable as a starting point to make one. Does not support topological changes in the meshes.
Soft bodies are physically represented by a set of ellipsoidal particles held together by shape-matching constraints. This way, they can deform both elastically (restoring their rest shape) or plastically (absorbing some of the deformations into their rest shape).