Box2D

This is the Box2D physics engine (v3) packaged for the Zig build system.

This aims to be the "easiest to use" Box2D wrapper for Zig.

It reexports all c functions and struct definitions but also provides a ziggified API including:

• Handle types are opaque enums (enum(u64){ _ }) instead of structs to be easily comparable. See World, Body, Shape, Chain, Joint.
• Methods on the handle types for convenience. So you can do World.create(&WorldDef.default() instead of b2CreateWorld(&b2DefaultWorldDef()).
• Enums for BodyType, ShapeType, JointType.
• Distinct handle types for Joints to increase type safety: DistanceJoint, FilterJoint, MotorJoint, MouseJoint, PrismaticJoint, WeldJoint, WheelJoint. All of them are just a Joint in box2d, but by making them distinct types we can provide different methods on all of them. You can convert any of them into a Joint by calling the joint() method on it, e.g to access methods available to all Joint types.
• I manually converted [*c]T to either *T, [*]T, or [*:0]u8 depdending on the context to make the API more clear for zig users.
• Removed the b2 prefix from a lot of struct types. If you see types or functions starting with b2 I have not gone over this part of the API yet. You can just use them, but they don't have a "nice" Zig interface yet.

Shout out to https://github.com/allyourcodebase/box2d for helping me get started with the bindings. But using it made the compile times too slow because it kept fetching data from the original Box2d repo. So instead I just copied the box2d/include and box2d/src directories directly into this repo. This keeps it all very lightweight and we don't have any dependencies.

This also means there is currently not samples application, sorry! Make your own.

Usage

Add the dependency to your build.zig.zon:

zig fetch --save git+https://github.com/tadeohepperle/box2d#main

Use the dependency in your build.zig:

pub fn build(b: *std.Build) void {
    const target = b.standardTargetOptions(.{});
    const optimize = b.standardOptimizeOption(.{});

    // define your game module and executable:
    const game_mod = b.createModule(.{
        .root_source_file = b.path("src/main.zig"),
        .target = target,
        .optimize = optimize,
    });
    const game_exe = b.addExecutable(.{
        .name = "game",
        .root_module = game_mod,
    });

    // add box2d as a dependency and add to the imports of the game module:
    const box2d = b.dependency("box2d", .{
        .target = target,
        .optimize = optimize,
    });
    game_mod.addImport("box2d", box2d.module("box2d"));
}

Import and use the module:

const box2d = @import(box2d);
pub fn main() void {
    const w = box2d.World.create(&box2d.WorldDef.default());
    std.debug.print("World Counters: {}\n", .{w.getCounters()});
}

Todo

• b2DynamicTree is not converted yet.
• it would be nice to let the user inject their own Vec2 types to have less friction when interacting with the API. Have not figured out yet what's the best way to do this.