Designing a physics engine in C++

[JeGX]

Physics engines are responsible for figuring out where each object in a scene is over time. Objects can collide with one another, then choose to respond in several ways. It's a generic problem that the user can configure at several different levels. Do they want a collider? Do they want to respond to collisions? Do they want to simulate dynamics? They could want dynamics, but not gravity. It's a problem that calls for good planning and robust design.

I looked at how bullet and box2d went about sorting their engines and concluded that the way bullet went about it was solid. I boiled it down to just what was needed, and based my design around that. There are already some great articles going over the hard math involved, so I am going to focus on the design aspect instead because I haven't seen anyone do that, and it's also a real headache.

At the current moment, this physics engine is not fully featured, but in future articles I plan to build it out further. This article will not cover rotation, multiple contact point collisions, or constrained simulation. I think it will work out for the best as it's easy to get overwhelmed, and I want to ease into those topics. With that out of the way, let's dive into the different parts of a physics engine.

The problem can be split into 2 or 3 pieces, dynamics, collision detection, and collision response. I'll start with dynamics because it is by far the simplest.

Link: https://blog.winter.dev/2020/designing-a-physics-engine/