Running BepuPhysis in Unity With NativeAOT Interlop

[sayiliromer]

Along with Unity users, i beleive running BepuPhysics inside Unit was a dream.
NativeAOT allows you to expose functions to unmanaged callers. So those functions can be called from any platforms that supports C interlops.
Here is a basic example by Mircosoft. https://github.com/dotnet/samples/tree/main/core/nativeaot/NativeLibrary

What i did is, i exposed some basic functions by wraping some BepuPhysics APIs.
I haven't done a performance comparison but i can tell it is reasonably good. Feels close to C# JIT version.
You can find a video of BepuPhysics runnind inside Unity at full speed.
Also, i included an example code if you want to try something similar.

    [UnmanagedCallersOnly(EntryPoint = "CreateSimulationInstance")]
    public static int CreateSimulationInstance()
    {
        var sim = Simulation
            .Create(
                _bufferPool,
                new NarrowPhaseCallbacks(new SpringSettings(30, 1)),
                new PoseIntegratorCallbacks(new Vector3(0, -10, 0)),
                new SolveDescription(8, 1));
        var instance = new SimInstance(sim, _bufferPool);

        int index;
        if (_emptyIndexes.Count != 0)
        {
            index = _emptyIndexes.Dequeue();
            _instances[index] = instance;
        }
        else
        {
            index = _instances.Count;
            _instances.Add(instance);
        }

        return index;
    }
    [UnmanagedCallersOnly(EntryPoint = "DestroySimulation")]
    public static bool DestroySimulation(int simId)
    {
        if (simId >= _instances.Count) return false;
        var simInstance = _instances[simId];
        simInstance.Dispose();
        _emptyIndexes.Enqueue(simId);
        _instances[simId] = default;
        return true;
    }
    [UnmanagedCallersOnly(EntryPoint = "AddBody")]
    public static int AddBody(int simId, PhysicsTransform transform, Vector3 velocity, BodyInertiaData inertiaData, uint packedShape, float sleepThreshold)
    {
        var bd = new BodyDescription()
        {
            Pose = new RigidPose(transform.Position,transform.Rotation),
            Velocity = velocity,
            LocalInertia = inertiaData.ReinterpretCast<BodyInertiaData, BodyInertia>(),
            Collidable = new TypedIndex() { Packed = packedShape },
            Activity = new BodyActivityDescription(sleepThreshold)
        };
        return _instances[simId].Simulation.Bodies.Add(bd).Value;
    }

[RossNordby]

Should be full performance if nativeaot is allowed to use AVX2, yup! Notably, there is a still-incomplete C API of this sort over in the abomination interop project, plus a partial C++ wrapper:
https://github.com/RossNordby/scratchpad/tree/main/Abomination/AbominationInterop/AbominationInterop