Ammo.js 自定义网格与球体碰撞

Posted 2023-02-15

【中文标题】Ammo.js 自定义网格与球体碰撞

【英文标题】：Ammo.js custom mesh collision with sphere

【发布时间】：2020-04-27 04:04:23

【问题描述】：

我正在尝试为每个对象/网格生成碰撞。它们都是静态的，应该与动态的球/球体碰撞。

我的代码如下所示：

const transform = new Ammo.btTransform();
transform.setIdentity();
transform.setOrigin(new Ammo.btVector3(-1.1726552248001099, 2.6692488193511963, 0));
transform.setRotation(new Ammo.btQuaternion(0.5, -0.5, 0.5, 0.4999999701976776));
const motionState = new Ammo.btDefaultMotionState(transform);

// Vertices and indices are parsed by GLTF parser by loaders.gl
const vertices = Entity.vertices;
const indices = Entity.indices;
const scale = [0.15933185815811157, 1.1706310510635376, 0.15933185815811157];

// btConvexHullShape or btBvhTriangleMeshShape, see below.

const localInertia = new Ammo.btVector3(0, 0, 0);

const rbInfo = new Ammo.btRigidBodyConstructionInfo(0, motionState, shape, localInertia);
const object = new Ammo.btRigidBody(rbInfo);

this._physicsWorld.addRigidBody(object);

我尝试了 2 种方法：btConvexHullShape 和 btBvhTriangleMeshShape 都不起作用。

btConvexHullShape

const shape = new Ammo.btConvexHullShape();
for (let i = 0; i < vertices.length / 3; i++) 
    shape.addPoint(new Ammo.btVector3(vertices[i * 3] * scale[0], vertices[i * 3 + 1] * scale[1], vertices[i * 3 + 2] * scale[2]));

使用 btConvexHullShape 的球体路径是这样的（它不会进入孔）：

我猜 Ammo.js 连接最高点？如何根据索引控制连接哪些点？看起来这种方法也很慢（30k个顶点需要一些时间），所以我尝试了：

btBvhTriangleMeshShape

const mesh = new Ammo.btTriangleMesh(true, true);
for (let i = 0; i * 3 < indices.length; i++) 
    mesh.addTriangle(
        new Ammo.btVector3(vertices[indices[i * 3]] * scale[0], vertices[indices[i * 3] + 1] * scale[1], vertices[indices[i * 3] + 2] * scale[2]),
        new Ammo.btVector3(vertices[indices[i * 3 + 1]] * scale[0], vertices[indices[i * 3 + 1] + 1] * scale[1], vertices[indices[i * 3 + 1] + 2] * scale[2]),
        new Ammo.btVector3(vertices[indices[i * 3 + 2]] * scale[0], vertices[indices[i * 3 + 2] + 1] * scale[1], vertices[indices[i * 3 + 2] + 2] * scale[2]),
        false
    );

const shape = new Ammo.btBvhTriangleMeshShape(mesh, true, true);

这个方法稍微好一点，但是球体在反弹一次时只是穿过物体（从圆圈反弹并穿过物体（红色圆圈））：

【参考方案1】：

btConvexHullShape 不起作用（尽管它周围的碰撞实际上起作用）的原因是它不适用于凹形。

至于 btBvhTriangleMeshShape，我一直在输入错误的顶点。我必须将索引乘以 3（因为每个顶点都有 3 个分量）。

这是完整的工作代码：

const transform = new Ammo.btTransform();
transform.setIdentity();
transform.setOrigin(new Ammo.btVector3(-1.1726552248001099, 2.6692488193511963, 0));
transform.setRotation(new Ammo.btQuaternion(0.5, -0.5, 0.5, 0.4999999701976776));
const motionState = new Ammo.btDefaultMotionState(transform);

// Vertices and indices are parsed by GLTF parser by loaders.gl
const vertices = Entity.vertices;
const indices = Entity.indices;
const scale = [0.15933185815811157, 1.1706310510635376, 0.15933185815811157];

const mesh = new Ammo.btTriangleMesh(true, true);
mesh.setScaling(new Ammo.btVector3(scale[0], scale[1], scale[2]));
for (let i = 0; i * 3 < indices.length; i++) 
    mesh.addTriangle(
        new Ammo.btVector3(vertices[indices[i * 3] * 3], vertices[indices[i * 3] * 3 + 1], vertices[indices[i * 3] * 3 + 2]),
        new Ammo.btVector3(vertices[indices[i * 3 + 1] * 3], vertices[indices[i * 3 + 1] * 3 + 1], vertices[indices[i * 3 + 1] * 3 + 2]),
        new Ammo.btVector3(vertices[indices[i * 3 + 2] * 3], vertices[indices[i * 3 + 2] * 3 + 1], vertices[indices[i * 3 + 2] * 3 + 2]),
        false
    );

const shape = new Ammo.btBvhTriangleMeshShape(mesh, true, true);

const localInertia = new Ammo.btVector3(0, 0, 0);

const rbInfo = new Ammo.btRigidBodyConstructionInfo(0, motionState, shape, localInertia);
const object = new Ammo.btRigidBody(rbInfo);

this._physicsWorld.addRigidBody(object);