This year I spoke at GTC about how a physics solver works. My intention was to provide a simple run-through of rigid bodies, constraints, and how they are used to pre-condition a solution. The presentation is meant to be comprehensive for everyone, so regardless of math background the information should be relatively easy to grasp. My hope is that this presentation will demystify how core solvers work. As a supplement to the presentation, I’ve provided source code for a simple 3D constraint solver which you can find on our nocturnal site. I encourage you to download the source code and experiment with it. I’d also like to point out that the solver does not have to be used for physics, as illustrated in my presentation.