I implemented a mass-spring system in C++ for my Physically Based Animation class in Fall 2019. Here are a few examples:

Cloth Simulation

Implements sphere and floor collision. Uses explicit integration.
Rendered in Houdini Mantra.

Slug

Implements meshing, floor collision. Uses implicit integration.
Rendered in Houdini Viewport.

Toads

Implements meshing, floor collision. Uses implicit integration.
Rendered in Houdini Viewport.