问题描述
我使用的是 Ammo.js，它是 C++ Bullet Physics 的直接 JavaScript 端口。不幸的结果是文档是 C++，如果您的语言是 Python 和 JavaScript，则不适合阅读。
我有 documentation for Ammo.btCompoundShape here 但无法理解。
我在这里有一个工作代码，其中 Bone 实例刚好从地板上掉下来，你会看到。不用担心“骨头”的命名，在这个开发阶段只是为了测试两个块的复合形状。
class RenderEngine {
constructor(gameEngine) {
this.gameEngine = gameEngine
this.gameEngine.clock = new THREE.Clock();
this.scene = new THREE.Scene();
this.scene.background = new THREE.Color(0xbfd1e5);
this.camera = new THREE.PerspectiveCamera(60,window.innerWidth / window.innerHeight,0.2,5000);
this.camera.position.set(0,30,70);
this.camera.lookAt(new THREE.Vector3(0,0));
const hemiLight = new THREE.HemisphereLight(0xffffff,0xffffff,0.1);
hemiLight.color.setHSL(0.6,0.6,0.6);
hemiLight.groundColor.setHSL(0.1,1,0.4);
hemiLight.position.set(0,50,0);
this.scene.add(hemiLight);
const dirLight = new THREE.DirectionalLight(0xffffff,1);
dirLight.color.setHSL(0.1,0.95);
dirLight.position.set(-1,1.75,1);
dirLight.position.multiplyScalar(100);
this.scene.add(dirLight);
dirLight.castShadow = true;
dirLight.shadow.mapSize.width = 2048;
dirLight.shadow.mapSize.height = 2048;
const d = 50;
dirLight.shadow.camera.left = -d;
dirLight.shadow.camera.right = d;
dirLight.shadow.camera.top = d;
dirLight.shadow.camera.bottom = -d;
dirLight.shadow.camera.far = 13500;
this.renderer = new THREE.Webglrenderer({
antialias: true
});
this.renderer.setClearColor(0xbfd1e5);
this.renderer.setPixelRatio(window.devicePixelRatio);
this.renderer.setSize(window.innerWidth,window.innerHeight);
document.body.appendChild(this.renderer.domElement);
this.renderer.shadowMap.enabled = true;
}
renderFrame() {
this.renderer.render(this.scene,this.camera)
}
}
class PhysicsEngine {
constructor(gameEngine,physicsEngine) {
this.gameEngine = gameEngine
let collisionConfiguration = new Ammo.btDefaultCollisionConfiguration(),dispatcher = new Ammo.btCollisiondispatcher(collisionConfiguration),overlappingPairCache = new Ammo.btDbvtbroadphase(),solver = new Ammo.btSequentialImpulseConstraintSolver();
this.tmpTrans = new Ammo.btTransform();
this.physicsWorld = new Ammo.btdiscreteDynamicsWorld(dispatcher,overlappingPairCache,solver,collisionConfiguration);
this.physicsWorld.setGravity(new Ammo.btVector3(0,-10,0));
}
updateFrame() {
this.physicsWorld.stepSimulation(this.gameEngine.clock.getDelta(),10);
this.gameEngine.objects.forEach(object => {
const ms = object.ammo.getMotionState()
if (ms) {
ms.getWorldTransform(this.tmpTrans)
const p = this.tmpTrans.getorigin()
const q = this.tmpTrans.getRotation()
object.mesh.position.set(p.x(),p.y(),p.z())
object.mesh.quaternion.set(q.x(),q.y(),q.z(),q.w())
}
})
}
}
class GameEngine {
constructor(renderEngine,physicsEngine) {
this.objects = []
this.renderEngine = new RenderEngine(this,renderEngine)
this.physicsEngine = new PhysicsEngine(this,physicsEngine)
}
run() {
this.physicsEngine.updateFrame()
this.renderEngine.renderFrame()
requestAnimationFrame(() => {
this.run()
});
}
add(object) {
this.objects.push(object)
return this.objects.length - 1
}
remove(objectIndex) {
this.objects[objectIndex] = false
}
}
class Box {
constructor(gameEngine,properties) {
this.gameEngine = gameEngine
this._initPhysics_(properties)
this._initRendering_(properties)
this.id = gameEngine.add(this)
}
_initPhysics_(properties) {
const pos = properties.pos
const quat = properties.quat
const scale = properties.scale
const mass = properties.mass
const group = properties.group
const interactionGroup = properties.interactionGroup
const physicsWorld = this.gameEngine.physicsEngine.physicsWorld
const transform = new Ammo.btTransform()
transform.setIdentity()
transform.setorigin(new Ammo.btVector3(pos.x,pos.y,pos.z))
transform.setRotation(new Ammo.btQuaternion(quat.x,quat.y,quat.z,quat.w))
const motionState = new Ammo.btDefaultMotionState(transform)
const colShape = new Ammo.btBoxShape(new Ammo.btVector3(scale.x * 0.5,scale.y * 0.5,scale.z * 0.5))
colShape.setMargin(0.05)
const localInertia = new Ammo.btVector3(0,0)
colShape.calculateLocalInertia(mass,localInertia)
const rbInfo = new Ammo.btRigidBodyConstructionInfo(mass,motionState,colShape,localInertia)
const body = new Ammo.btRigidBody(rbInfo)
physicsWorld.addRigidBody(body,group,interactionGroup)
this.ammo = body
}
_initRendering_(properties) {
const pos = properties.pos
const scale = properties.scale
const color = properties.color
this.mesh = new THREE.Mesh(new THREE.BoxBufferGeometry(),new THREE.MeshphongMaterial({
color
}))
this.mesh.position.set(pos.x,pos.z)
this.mesh.scale.set(scale.x,scale.y,scale.z)
this.mesh.castShadow = true
this.mesh.receiveShadow = true
this.gameEngine.renderEngine.scene.add(this.mesh)
}
}
class Bone {
constructor(gameEngine,properties) {
this.gameEngine = gameEngine
this._initPhysics_(properties)
this._initRendering_(properties)
this.id = gameEngine.add(this)
}
_initPhysics_(properties) {
const pos = properties.pos
const quat = properties.quat
const scale = properties.scale
const mass = properties.mass
const group = properties.group
const interactionGroup = properties.interactionGroup
const physicsWorld = this.gameEngine.physicsEngine.physicsWorld
const compoundShape = new Ammo.btCompoundShape()
this._addSection_(compoundShape,{
pos,quat,scale,offset: {
x: 0,y: 0,z: 0
},rotation: {
x: 0,z: 0,w: 0
}
})
this._addSection_(compoundShape,w: 0
}
})
const transform = new Ammo.btTransform()
transform.setIdentity()
transform.setorigin(new Ammo.btVector3(pos.x,quat.w))
const motionState = new Ammo.btDefaultMotionState(transform)
compoundShape.setMargin(0.05)
const localInertia = new Ammo.btVector3(0,0)
compoundShape.calculateLocalInertia(mass,compoundShape,scale.z)
this.mesh.castShadow = true
this.mesh.receiveShadow = true
this.gameEngine.renderEngine.scene.add(this.mesh)
}
_addSection_(compoundShape,properties) {
const pos = properties.pos
const quat = properties.quat
const scale = properties.scale
const offset = properties.offset
const rotation = properties.rotation
const transform = new Ammo.btTransform()
transform.setIdentity()
transform.setorigin(new Ammo.btVector3(pos.x + offset.x,pos.y + offset.y,pos.z + offset.z))
transform.setRotation(new Ammo.btQuaternion(quat.x + rotation.x,quat.y + rotation.y,quat.z + rotation.z,quat.w + rotation.w))
const motionState = new Ammo.btDefaultMotionState(transform)
const colShape = new Ammo.btBoxShape(new Ammo.btVector3(scale.x * 0.5,scale.z * 0.5))
compoundShape.addChildShape(transform,colShape)
}
}
Ammo().then((Ammo) => {
const gameEngine = new GameEngine(THREE,Ammo)
const plane = new Box(gameEngine,{
pos: {
x: 0,z: 0
},quat: {
x: 0,w: 1
},scale: {
x: 50,y: 2,z: 50
},mass: 0,group: 1,interactionGroup: 1,color: 0xa0afa4
})
const Box1 = new Box(gameEngine,y: 5,scale: {
x: 2,z: 2
},mass: 1,color: 0xa0afa4
})
const Box2 = new Box(gameEngine,{
pos: {
x: 0.75,y: 8,z: 0.75
},color: 0xa0afa4
})
const bone1 = new Bone(gameEngine,{
pos: {
x: -0.75,y: 10,z: -0.75
},color: 0xa0afa4
})
console.log("gameEngine",gameEngine)
gameEngine.run()
})canvas,body,html {
margin: 0px;
padding: 0px;
overflow: hidden;
}<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r124/three.min.js"></script>
<script src="https://cdn.babylonjs.com/ammo.js"></script>两个 Box 实例落在地板上 (plane)，bone1 落下。我想我在 Ammo.btCompoundShape 上做错了什么。没有错误。正确的做法是什么？
解决方法
bone 实际上并没有完全落下，而是停在了飞机的中间。
原因：您正在转换两次：
-
motionState已转换 -
compoundShape在_addSection_ 内再次转换
这样 compoundShape 确实发生碰撞并且不会落下，但是可见的 colShape 被偏移（从 compoundShape 的参考位置）到 plane 内部.
您可以看到，如果您尝试更改 _addSection_ 中的这一行：
transform.setOrigin(new Ammo.btVector3(0,2.0))
解决方案：
不要变换两次。例如。仅变换 motionState，而不变换 compoundShape。
例如。删除这两行：
_addSection_(compoundShape,properties) {
const transform = new Ammo.btTransform()
transform.setIdentity()
// -- disable second transform: --
// transform.setOrigin(new Ammo.btVector3( ... ))
// transform.setRotation(new Ammo.btQuaternion( ... ))
const colShape = new Ammo.btBoxShape(new Ammo.btVector3(scale.x * 0.5,scale.y * 0.5,scale.z * 0.5))
compoundShape.addChildShape(transform,colShape)
}
另一条评论：
localInertia 也应用于两次：
-
compoundShape.calculateLocalInertia(mass,localInertia)和 -
const rbInfo = new Ammo.btRigidBodyConstructionInfo(mass,motionState,compoundShape,localInertia)。
这显然有效，但可能不是故意的。它不会失败，因为它是 0,0。如果您确实想要两个惯性，我也认为您不能为它们使用相同的 localInertia 对象，但您应该创建第二个对象，例如localInertiaCompoundShape，但我不确定。