🎳 physx-sys

Unsafe automatically-generated Rust bindings for NVIDIA PhysX 4.1 C++ API.

Please also see the repository containing a work-in-progress safe wrapper.

Presentation

Tomasz Stachowiak did a presentation at the Stockholm Rust Meetup on October 2019 about this project that goes through the technical details of how C++ to Rust bindings of physx-sys works:

Basic usage

unsafe {
    let foundation = physx_create_foundation();
    let physics = physx_create_physics(foundation);

    let mut scene_desc = PxSceneDesc_new(PxPhysics_getTolerancesScale(physics));
    scene_desc.gravity = PxVec3 {
        x: 0.0,
        y: -9.81,
        z: 0.0,
    };

    let dispatcher = PxDefaultCpuDispatcherCreate(2, null_mut());

    scene_desc.cpuDispatcher = dispatcher as *mut PxCpuDispatcher;
    scene_desc.filterShader = Some(PxDefaultSimulationFilterShader);

    let scene = PxPhysics_createScene_mut(physics, &scene_desc);

    // Your physics simulation goes here
}

Examples

Ball

A simple example to showcase how to use physx-sys. It can be run with cargo run --examples ball.

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How it works

The binding is generated using a custom C++ app written against clang's libtooling. It queries the compiler's abstract syntax tree, and maps the C++ PhysX functions and types to Rust using heuristics chosen specifically for this SDK. It is not a general C++ <-> Rust binding generator, and using it on other projects will likely crash and burn.

Since C++ does not have a standardized and stable ABI, it's generally not safe to call it from Rust code; since PhysX exposes a C++ interface, we can't use it directly. That's why physx-sys generates both a Rust interface as well as a plain C wrapper. The C code is compiled into a static library at build time, and Rust then talks to C.

In order to minimize the amount of work required to marshall data between the C wrapper and the original C++ API, we generate a bespoke C wrapper for each build target. The wrapper is based on metadata about structure layout extracted directly from compiling and running a tiny program against the PhysX SDK using the specific C++ compiler used in the build process.

The build process comprises a few steps:

The pxbind utility uses clang to extract metadata about PhysX functions and types, and generates partial Rust and C bindings as physx_generated.hpp and physx_generated.rs. Those contain all function definitions, and a small subset of types. It also generates a C++ utility called structgen by emitting structgen.cpp.
structgen is compiled against the PhysX SDK, and generates all the remaining type wrappers. For each struct, it queries the size and offset of its members, and generates structgen_out.hpp and structgen_out.rs. The types are "plain old data" structs which will perfectly match the memory layout of the C++ types.
All the generated C types are compiled together to form physx_api, a static library for Rust to link with.
The Rust wrapper is compiled, and linked with PhysX and the C wrapper.

Steps 2..4 are performed completely automatically from within build.rs, while step 1 is only necessary when upgrading the PhysX SDK or modifying the generator. As such, building and running pxbind is a manual task, and is currently only supported on *nix systems.

License

Licensed under either of

Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Note that the PhysX C++ SDK has it's own BSD 3 license and depends on additional C++ third party libraries.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

physx-sys 0.4.9