https://github.com/jon-edward/box2d.nim
Nim bindings for Erin Catto's Box2D physics engine.
https://github.com/jon-edward/box2d.nim
box2d-physics-engine game-development nim physics
Last synced: about 1 month ago
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Nim bindings for Erin Catto's Box2D physics engine.
- Host: GitHub
- URL: https://github.com/jon-edward/box2d.nim
- Owner: jon-edward
- License: mit
- Created: 2024-06-24T23:29:19.000Z (11 months ago)
- Default Branch: main
- Last Pushed: 2024-10-24T01:06:30.000Z (7 months ago)
- Last Synced: 2024-10-24T16:05:18.323Z (7 months ago)
- Topics: box2d-physics-engine, game-development, nim, physics
- Language: Nim
- Homepage: https://jon.is-a.dev/box2d.nim/
- Size: 422 KB
- Stars: 6
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# box2d.nim
Nim bindings for Erin Catto's [Box2D](https://github.com/erincatto/box2d) physics engine.
## Installation
```
nimble install box2d
```
## Documentation
See library documentation [here](https://jon-edward.github.io/box2d.nim/). Also,
because the library's naming is largely consistent with that of Box2D, you can use the
[Box2D documentation](https://box2d.org/documentation/) directly.
The only exception to the naming consistency is `b2BodyDef.type` being translated to `b2BodyDef.bodyType`
because of the reserved `type` keyword in Nim.
## Testing
There are most of Box2D's unit tests translated to Nim in the
[tests](https://github.com/jon-edward/box2d.nim/tree/main/tests) directory. In addition, there are larger examples
using [naylib](https://github.com/planetis-m/naylib) for rendering in the [examples](https://github.com/jon-edward/box2d.nim/tree/main/examples)
directory.
Building and testing is done for `ubuntu-latest`, `windows-latest`, and `macos-latest` GitHub runners per release.
## Simple example
Box2D passes the user IDs for creating, manipulating, and reading world members such as shapes and bodies. The properties
of these members are stored in various -`Def` types, such as [`b2BodyDef`](https://jon-edward.github.io/box2d.nim/box2d/wrapper.html#b2BodyDef).
Making a dynamic body with a box shape is as simple as defining a world with a given gravity vector, creating a dynamic body in that world,
attaching it to a shape, and stepping the simulation forward.
Notice that -`Def` types are used only for passing to `b2Create`- functions,
and opaque -`Id` objects (`worldId`, `bodyId`) are retained.
```nim
import box2d
# Create world definition
var worldDef = b2DefaultWorldDef()
worldDef.gravity = b2Vec2(x: 0.0f, y: -10.0f)
# Create world from definition
let worldId = b2CreateWorld(worldDef.addr)
# worldDef no longer needed
# Create body definition
var bodyDef = b2DefaultBodyDef()
bodyDef.bodyType = b2_dynamicBody
bodyDef.position = b2Vec2(x: 0.0f, y: 4.0f)
# Create body from definition
let bodyId = b2CreateBody(worldId, bodyDef.addr)
# bodyDef no longer needed
# Create polygon (indirectly through b2MakeSquare)
let dynamicBox = b2MakeSquare(1.0f)
# Create shape definition
var shapeDef = b2DefaultShapeDef()
shapeDef.density = 1.0f
shapeDef.friction = 0.3f
# Add polygon to simulation using body, shape definition, and box
discard b2CreatePolygonShape(bodyId, shapeDef.addr, dynamicBox.addr)
# shapeDef and dynamicBox no longer needed
# C wrappers need C types, such as cfloats and cints
let timeStep: cfloat = 1/60
let subStepCount: cint = 4
# Step simulation 60 times
for _ in 0..<60:
b2World_Step(worldId, timeStep, subStepCount)
# Check that the box fell
echo "Dynamic box y-position: ", b2Body_GetPosition(bodyId).y
# Cleanup
b2DestroyBody(bodyId)
b2DestroyWorld(worldId)
```