bullet3

For typical game physics engines... not that much. Math libraries like Eigen or Blaze use lots of template metaprogramming techniques under the hood that can help when you're doing large batched matrix multiplications (since it can remove temporary allocations at compile-time and can also fuse operations efficiently, as well as applying various SIMD optimizations), but it doesn't really help when you need lots of small operations (with mat3 / mat4 / vec3 / quat / etc.). Typically game physics engines tend to use iterative algorithms for their solvers (Gauss-Seidel, PBD, etc...) instead of batched "matrix"-oriented ones, so you'll get less benefits out of Eigen / Blaze compared to what you typically see in deep learning / scientific computing workloads. The codebases I've seen in many game physics engines seem to all roll their own minimal

To use bullet physics as a hypothetical example, if my game was the hello world example [0], I would expect that practically that entire file would be un-distributable. [0] https://github.com/bulletphysics/bullet3/blob/master/example...

It is still going strong and being actively developed : https://github.com/bulletphysics/bullet3 & https://pybullet.org/wordpress/

The naive integrator you're describing, just taking the differential equations and substituting dt by a small, non-zero time step, is known as the Euler integrator [1]. As you say, this scheme does not keep energy invariant. In fact, energy may grow unbounded if you use it. The simplest integrator that "preserves" energy is the Symplectic Euler [2] integrator, which reads: v <- v + F/m * dt x <- x + v * dt The key is that you use the updated velocity to update the position in the same time step. In this scheme, energy isn't exactly preserved, it varies a little bit from one time step to the next. However, you can guarantee that the energy fluctuations will remain bounded, if your time step is below a (fairly large) critical value. Reading the code of this blog post, the first version of the Step (at the beginning of the blogpost) uses t

I do agree, this is one of the many improvementents/experimentation the project needs. Actually, the Minitaur example come with a torque controller implementation (https://github.com/bulletphysics/bullet3/blob/master/example...), needs tests. btw I'm going to use a Jetson mini as controller!! :)

try start with this: https://github.com/bulletphysics/bullet3 there are others. google it. to perfect physics you must understand the real math of physics, but it probably won't fit in a game. game physics libraries are subsets of real physics.

I don't know about game libraries in particular, but in general, it's pretty common for C++ libraries to ship with a C api, and for most non-C++ languages to use that as the basis for their integration. It looks like several (https://code.google.com/p/bullet/issues/detail?id=43) people (https://github.com/bulletphysics/bullet3/issues/130) have written C apis for bullet already, for that reason. Vala, .NET, LuaJIT and Rust all get mentioned.