你不能单独使用Physijs进行碰撞检测。它只是完全配备了实时物理模拟，基于amo .js库。当你将网格的质量设置为0时，它使它们成为静态的。然后，它们对外力没有反应，例如碰撞响应(即在检测到碰撞后施加在网格上的速度变化)或重力。另外，两个相互重叠的静态网格不会触发碰撞事件。

方案A:直接使用amo .js

从Bullet Physics移植过来，这个库提供了生成物理模拟的必要工具，或者只是检测定义形状之间的碰撞(Physijs不想让我们看到)。下面是检测两个刚性球体之间碰撞的代码片段:

var bt_collision_configuration;
var bt_dispatcher;
var bt_broadphase;
var bt_collision_world;
var scene_size = 500;
var max_objects = 10; // Tweak this as needed
bt_collision_configuration = new Ammo.btDefaultCollisionConfiguration();
bt_dispatcher = new Ammo.btCollisionDispatcher(bt_collision_configuration);
var wmin = new Ammo.btVector3(-scene_size, -scene_size, -scene_size);
var wmax = new Ammo.btVector3(scene_size, scene_size, scene_size);
// This is one type of broadphase, Ammo.js has others that might be faster
bt_broadphase = new Ammo.bt32BitAxisSweep3(
        wmin, wmax, max_objects, 0, true /* disable raycast accelerator */);
bt_collision_world = new Ammo.btCollisionWorld(bt_dispatcher, bt_broadphase, bt_collision_configuration);
// Create two collision objects
var sphere_A = new Ammo.btCollisionObject();
var sphere_B = new Ammo.btCollisionObject();
// Move each to a specific location
sphere_A.getWorldTransform().setOrigin(new Ammo.btVector3(2, 1.5, 0));
sphere_B.getWorldTransform().setOrigin(new Ammo.btVector3(2, 0, 0));
// Create the sphere shape with a radius of 1
var sphere_shape = new Ammo.btSphereShape(1);
// Set the shape of each collision object
sphere_A.setCollisionShape(sphere_shape);
sphere_B.setCollisionShape(sphere_shape);
// Add the collision objects to our collision world
bt_collision_world.addCollisionObject(sphere_A);
bt_collision_world.addCollisionObject(sphere_B);
// Perform collision detection
bt_collision_world.performDiscreteCollisionDetection();
var numManifolds = bt_collision_world.getDispatcher().getNumManifolds();
// For each contact manifold
for(var i = 0; i < numManifolds; i++){
    var contactManifold = bt_collision_world.getDispatcher().getManifoldByIndexInternal(i);
    var obA = contactManifold.getBody0();
    var obB = contactManifold.getBody1();
    contactManifold.refreshContactPoints(obA.getWorldTransform(), obB.getWorldTransform());
    var numContacts = contactManifold.getNumContacts();
    // For each contact point in that manifold
    for(var j = 0; j < numContacts; j++){
        // Get the contact information
        var pt = contactManifold.getContactPoint(j);
        var ptA = pt.getPositionWorldOnA();
        var ptB = pt.getPositionWorldOnB();
        var ptdist = pt.getDistance();
        // Do whatever else you need with the information...
    }
}
// Oh yeah! Ammo.js wants us to deallocate
// the objects with 'Ammo.destroy(obj)'

我把这段c++代码转换成JS代码。可能有一些语法缺失，所以你可以检查amo .js API绑定的更改是否有任何不工作的地方。

方案B:使用THREE的光线投射器

光线投射器不太精确，但可以在你的形状中添加额外的顶点计数来更精确。下面是一些检测两个框之间碰撞的代码:

// General box mesh data
var boxGeometry = new THREE.CubeGeometry(100, 100, 20, 1, 1, 1);
var boxMaterial = new THREE.MeshBasicMaterial({color: 0x8888ff, wireframe: true});
// Create box that detects collision
var dcube = new THREE.Mesh(boxGeometry, boxMaterial);
// Create box to check collision with
var ocube = new THREE.Mesh(boxGeometry, boxMaterial);
// Create ray caster
var rcaster = new THREE.Raycaster(new THREE.Vector3(0, 0, 0), new THREE.Vector3(0, 1, 0));
// Cast a ray through every vertex or extremity
for(var vi = 0, l = dcube.geometry.vertices.length; vi < l; vi++){      
    var glovert = dcube.geometry.vertices[vi].clone().applyMatrix4(dcube.matrix);
    var dirv = glovert.sub(dcube.position);
    // Setup ray caster
    rcaster.set(dcubeOrigin, dirv.clone().normalize());
    // Get collision result
    var hitResult = rcaster.intersectObject(ocube);
    // Check if collision is within range of other cube
    if(hitResult.length && hitResult[0].distance < dirv.length()){ 
        // There was a hit detected between dcube and ocube
    }
}

查看这些链接以获取更多信息(可能还有它们的源代码):

• Three.js-Collision-Detection
• 使用Three.js进行基本的碰撞检测，光线投射
• THREE's ray caster docs