box2d
Overview
This library is used for game development to make the object motion more realistic and the game scenes more interactive, such as Angry Birds.
Display Effects
How to Install
ohpm install @ohos/box2d
For details, see Installing an OpenHarmony HAR.
How to Use
import * as box2d from '@ohos/box2d'
...
aboutToAppear() {
selectArr = [];
for (let i: number = 0; i < g_testEntries.length; ++i) {
let o = {};
o['value'] = g_testEntries[i].name;
selectArr[i] = o;// Initialize data.
}
// Invoke rendering cyclically.
this.init();
}
private init() {
setTimeout(inits, timeStep);
}
const inits = function (time) {
setTimeout(loop, timeStep);
}
const loop = function (time) {
setTimeout(loop, timeStep);
app.SimulationLoop(time);
}
...
// Switch the animation.
Select(selectArr)
.selected(this.index)
.value(selectArr[this.index].value)
.font({ size: 20, weight: 200, family: 'serif', style: FontStyle.Normal })
.selectedOptionFont({ size: 30, weight: 300, family: 'serif', style: FontStyle.Normal })
.optionFont({ size: 20, weight: 200, family: 'serif', style: FontStyle.Normal })
.onSelect((index: number) => {
this.index = index;
if (app) {
app.m_test_index = index;
// Load the animation.
app.LoadTest();
}
})
Available APIs
b2Body APIs
-
Creates a fixture.
CreateFixture(def: b2FixtureDef): b2Fixture• Input: def - Fixture definition (shape, density, friction, etc.)
• Output: Newly created fixture object -
Destroys a fixture.
DestroyFixture(fixture: b2Fixture): void
• Input: fixture - Fixture object to destroy
• Output: None -
Sets the transformation.
SetTransform(position: XY): void
• Input: position - World coordinate position
• Output: None -
Obtains the transformation.
GetTransform(): b2Transform
• Output: Current body's transformation matrix (position and angle) -
Obtains the position. GetPosition(): b2Vec2
• Output: World coordinates of body's center -
Sets the position.
SetPosition(position: XY): void
• Input: position - Target world coordinates
• Output: None -
Obtains the world center.
GetWorldCenter(): b2Vec2
• Output: World coordinates of body's centroid -
Obtains the local center.
GetLocalCenter(): b2Vec2
• Output: Offset of centroid relative to local coordinate system -
Sets the linear speed.
SetLinearVelocity(velocity: XY): void
• Input: velocity - Target linear velocity vector
• Output: None
b2World APIs
-
Sets the substep.
setSubStepping(flag: boolean): void
• Input: flag - Whether to enable sub-stepping (for complex simulations)
• Output: None -
Sets the destruction listener.
SetDestructionListener(listener: b2DestructionListener | null): void
• Input: listener - Callback interface (handles object destruction events)
• Output: None -
Sets the contact filter.
SetContactFilter(filter: b2ContactFilter): void
• Input: filter - Callback interface (determines collision allowance)
• Output: None -
Sets the contact listener.
SetContactListener(listener: b2ContactListener): void
• Input: listener - Callback interface (handles collision events)
• Output: None -
Sets the debugging drawing.
SetDebugDraw(debugDraw: b2Draw | null): void
• Input: debugDraw - Debug drawing interface
• Output: None -
Creates a rigid body.
CreateBody(def: b2BodyDef): b2Body
• Input: def - Body definition (type, position, damping, etc.)
• Output: Newly created body object -
Destroys a rigid body.
DestroyBody(body: b2Body): void
• Input: body - Body to destroy
• Output: None -
Creates a joint.
CreateJoint(def: b2JointDef): b2Joint
• Input: def - Joint definition (connected bodies, anchors, etc.)
• Output: Newly created joint object -
Destroys a joint.
DestroyJoint(joint: b2Joint): void
• Input: joint - Joint to destroy
• Output: None
b2Contact APIs
-
Performs a reset.
Reset(): void
• Output: None (resets contact state) -
Obtains the manifold.
GetManifold(): b2Manifold• Output: Collision manifold data (contact point collection) -
Obtains the world manifold.
GetWorldManifold(worldManifold: b2WorldManifold): void
• Input/Output: worldManifold - Stores manifold data in world coordinates -
Sets the tangent speed.
SetTangentSpeed(speed: number): void
• Input: speed - Tangential velocity value
• Output: None -
Resets the friction.
ResetFriction(): void
• Output: None (restores default friction) -
Set the friction.
SetFriction(friction: number): void
• Input: friction - New friction coefficient
• Output: None -
Specifies whether to enable the function.
SetEnabled(flag: boolean): void
• Input: flag - Whether to enable contact
• Output: None -
Obtains fixture A.
GetFixtureA(): b2Fixture
• Output: First fixture in the contact
b2Shape APIs
-
Performs a ray cast.
RayCast(output: b2RayCastOutput, input: b2RayCastInput, transform: b2Transform, childIndex: number): boolean
• Input: input - Ray parameters; transform - Transformation matrix; childIndex - Child shape index
• Output: output - Stores intersection info; returns whether hit occurred -
Obtains the type.
GetType(): b2ShapeType
• Output: Shape type enum (circle, polygon, etc.) -
Performs a copy.
Copy(other: b2Shape): b2Shape
• Output: Returns a deep copy of the shape -
Obtains the child count.
GetChildCount(): number
• Output: Number of child shapes (for composite shapes) -
Computes AABB.
ComputeAABB(aabb: b2AABB, xf: b2Transform, childIndex: number): void
• Input: xf - Transformation matrix; childIndex - Child shape index
• Output: aabb - Stores computation results -
Computes the quality.
ComputeMass(massData: b2MassData, density: number): void
• Input: density - Density value
• Output: massData - Stores mass, centroid, etc. -
Computes the distance.
ComputeDistance(xf: b2Transform, p: b2Vec2, normal: b2Vec2, childIndex: number): number
• Input: xf - Transformation matrix; p - Point in world coordinates; normal - Direction of increasing distance; childIndex - the child shape index
• Output: Minimum distance -
Performs a clone.
clone(): b2Shape
• Output: Returns new instance (same as Copy)
About obfuscation
- Code obfuscation, please seeCode Obfuscation
- If you want the box2d library not to be obfuscated during code obfuscation, you need to add corresponding exclusion rules in the obfuscation rule configuration file obfuscation-rules.txt：
-keep
./oh_modules/@ohos/box2d
Constraints
box2d has been verified in the following version:
-
DevEco Studio Version: 4.1 Canary (4.1.3.317)
-
OpenHarmony SDK: API11 (4.1.0.36)
Directory Structure
|---- box2d
| |---- entry
| |----src
| |----main
| |----ets
| |----pages
| |----Index.ets # Main page
| |----Testbed
| |----Framework
| |----DebugDraw.ets # Core code for effect drawing
| |----FullscreenUI.ts # Global page initiaization with particle parameters
| |----Main.ets # Entry to effect drawing
| |----ParticleEmitter.ts # Particle emitter
| |----ParticleParameter.ts # Particle parameters
| |----Test.ets # Canvas initialization settings
| |----Tests # Implementation of all effects
| |----Testbed.ts # External APIs
| |---- library # box2d core library
| |----src
| |----main
| |----ets
| |----Box2D
| |----Collision # Collision directory
| |----Shapes # Shape directory
| |----b2ChainShape.ts # Chain shape
| |----b2CircleShape.ts # Circle shape
| |----b2EdgeShape.ts # Edge shape
| |----b2PolygonShape.ts # Polygon shape
| |----b2Shape.ts # Shape abstraction class
| |----b2BroadPhase.ts # Broad-phase
| |----b2CollideCircle.ts # Circle collision
| |----b2CollideEdge.ts # Edge collision
| |----b2CollidePolygon.ts # Polygon collision
| |----b2Collision.ts # Collision class
| |----b2Distance.ts # Distance class
| |----b2DynamicTree.ts # Dynamic tree
| |----b2TimeOfImpact.ts # Time of impact
| |----Common # Common code: drawing, setting, and timer
| |----b2BlockAllocator.ts # Block allocator
| |----b2Draw.ts # Drawing class
| |----b2GrowableStack.ts # Growable stack
| |----b2Math.ts # Math class
| |----b2Settings.ts # Setting class
| |----b2StackAllocator.ts # Stack allocator
| |----b2Timer.ts # Timer class
| |----Controllers # Controller directory
| |----b2BuoyancyController.ts # Buoyancy controller
| |----b2ConstantAccelController.ts # Constant acceleration controller
| |----b2ConstantForceController.ts # Constant force controller
| |----b2Controller.ts # Gravity controller
| |----b2GravityController.ts # Tensor damping controller
| |----Dynamics
| |----Contacts # Contact directory
| |----Joints # Joints
| |----b2Body.ts # Body
| |----b2ContactManager.ts # Contact management
| |----b2Fixture.ts # Fixtures
| |----b2Island.ts # Islands
| |----b2TimeStep.ts # Time steps
| |----b2World.ts # World
| |----b2WorldCallbacks.ts # World callbacks
| |----Particle # Particle directory
| |----b2Particle.ts # Particles
| |----b2ParticleGroup.ts # Particle groups
| |----b2ParticleSystem.ts # Particle systems
| |----b2StackQueue.ts # Stack queues
| |----b2VoronoiDiagram.ts # Voronoi diagrams
| |----Rope # Rope directory
| |----b2Rope.ts # Ropes
| |----Box2D.ts # API export
| |----box2d.umd.js # API export implementation
| |---- README.md # Readme
| |---- README_zh.md # Readme
How to Contribute
If you find any problem when using box2d, submit an Issue or a PR.
License
This project is licensed under MIT License.