This is a simulation of two rigid bodies connected to form a double pendulum.
You can change parameters in the simulation such as gravity, initial angle of the two bodies.
The standard Double Pendulum simulation shows an idealized situation with massless rods that have point masses at their ends. In contrast, this simulation shows more realistic rigid bodies, with the center of gravity being anywhere on the body.
See Compare Double Pendulum to see this simulation running alongside the equivalent setup using the 2D Rigid Body Physics Engine. In contrast to the physics engine, this is a specialized simulation that only runs this particular setup, though there is flexibility about the sizes of the two bodies and how they are connected to each other.
For derivation of equations of motion, see the paper Double Pendulum as Rigid Bodies by Erik Neumann, April 2, 2011.
Also available are: open source code, documentation and a simple-compiled version which is more customizable.
This web page was first published November 2016.