sash-a / Bullet.jl

Bullet.jl

Code Generation

Raw

src/generator/bullet_parse_headers.jl makes Julia wrappers to call the Bullet C API (b3 functions).

e.g.

sm = Bullet.Raw.b3ConnectPhysicsDirect()

Warning, these functions are thin wrappers around ccall calls. If you pass a [1, 1, 1] where the Bullet API expects a Ptr{Cdouble}, Bullet will see [5.0e-324, 5.0e-324, 5.0e-324].

Safe

src/generator/make_julian_api.jl makes Julia wrappers that are safer and more Julian (using e.g. ColorTypes)

e.g.

sm = Bullet.Raw.b3ConnectPhysicsDirect()
command = Bullet.Raw.b3InitPhysicsParamCommand(sm)
Bullet.Safe.PhysicsParamSetGravity(command, [0, 0, -9.8])
#= equivalent to Bullet.Raw.b3PhysicsParamSetGravity(commandHandle, 0, 0, -9.8) =#

C or C++

This package illustrates two different methods of interfacing with Bullet. There is the core physics code written afaik entirely in C++, and a command processor (running in its own POSIX process) that handles a special-made protocol (which could be over shared memory, or the network), and then there's C code for sending/receiving command messages. This is the way that pybullet works. It's C code that uses the Python C API to expose a Python interface to the C code for sending/receive command messages.

There are aspects of the C++ code that are not exposed via the command processor (after all, it's supposed to be a sort of abstraction over at least some parts of the specific engine implementation), and this package tries to demonstrate how to use Cxx.jl for that purpose.

Note that pybullet, taken to mean what I described above, does not do any physics calculation, and goretkin/Bullet.jl roughly rewrites at least part of what resembles PyBullet. Except that it's a bit better, because our ecosystem has some packages like ColorTypes.jl, Rotations.jl, GeometryTypes.jl that aim to be used in interfaces. So Bullet.jl tries to be fancy by taking a Bullet C API function like e.g. setOrientation(Float x, Float y, Float z, Float w) and turn it into setOrientation(r::Rotation) and then you can use whatever parameterization of rotation (quaternion, rpy, ...) you'd like.