使用 .intersect/.intersectsBox 进行对象碰撞threeJS

Question

您好，我正在用 threeJS 开发一个基本的突围/打砖块游戏。现在我只有一个桨和一个在屏幕上弹跳的球。我试图让碰撞工作，以便当球击中桨时，它会弹开。我一直在尝试使用边界框来实现这一点，但是我遇到了一个问题，即 .intersect/.intersectsBox 没有正确注册交叉点，我不知道为什么。以下是我到目前为止的代码 -

const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);

const renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

const geometry = new THREE.BoxGeometry(5, 1, 1);
const material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });
const cube = new THREE.Mesh(geometry, material);
var cubeBoxHelper = new THREE.BoxHelper(cube, 0xff0000);
var boundingBoxPaddle = new THREE.Box3().setFromObject(cubeBoxHelper);
cubeBoxHelper.update();

const geometrySphere = new THREE.SphereGeometry(1, 32, 32);
const materialSphere = new THREE.MeshBasicMaterial({ color: 0xffff00 });
const sphere = new THREE.Mesh(geometrySphere, materialSphere);
var sphereBoxHelper = new THREE.BoxHelper(sphere, 0xff0000);
var boundingBoxBall = new THREE.Box3().setFromObject(sphereBoxHelper);
sphereBoxHelper.update();

scene.add(cube, cubeBoxHelper, sphere, sphereBoxHelper);

sphere.position.y = 5;
camera.position.z = 15;
camera.position.y = 10;

var xSpeed = 0.0005;
var dx = 0.1;
var dy = 0.1;

function bounce()
{
    if (sphere.position.x < -19 || sphere.position.x > 18.5)
    {
        dx = -dx;
    }
    if (sphere.position.y < -5 || sphere.position.y > 19)
    {
        dy = -dy;
    }
    sphere.position.x += dx;
    sphere.position.y += dy;
    sphereBoxHelper.update();
}

function intersect()
{
    if (boundingBoxBall.intersect(boundingBoxPaddle) == true)
    {
        console.log("intersection");
    }
}

const animate = function ()
{
    requestAnimationFrame(animate);

    document.addEventListener("keydown", onDocumentKeyDown, false);
    function onDocumentKeyDown(event)
    {
        var keyCode = event.which;
        if (keyCode == 65 && cube.position.x >= -18.5)
        {
            cube.position.x -= xSpeed;
        }
        else if (keyCode == 68 && cube.position.x <= 18)
        {
            cube.position.x += xSpeed;
        }
        cubeBoxHelper.update();
    };
    bounce();
    intersect();
    sphereBoxHelper.update();
    renderer.render(scene, camera);
};

animate();

现在我已经设置了，所以 intersect 函数只记录到控制台，这样我就可以知道发生了什么。任何帮助都会很棒，因为我不确定自己做错了什么。

Answer 1

Box3.intersect

.intersect ( box : Box3 ) : this box - 要与之相交的框。

计算 this 和 box 的交集，将此框的上界设置为两个框的上界中较小的一个，并将此框的下界设置为两个框的下界中较大的一个。如果没有重叠，则将此框设为空。

这个函数实际上是用来自boundingBoxPaddle 的信息更新boundingBoxBall，甚至可能将boundingBoxBall 设置为一个空框！

我认为你真正追求的功能是：

Box3.intersectsBox

.intersectsBox ( box : Box3 ) : Boolean box - 检查交叉点的框。

确定此框是否与框相交。

intersectsBox 函数返回一个简单的true/false，因此您可以判断两个框是否碰撞。

另请注意，您的边界框是相对于关联的几何图形的。如果您转换Mesh，那么您还需要转换边界框。 Box3 docs 上的示例代码实际上突出显示了这一点：

const box = new THREE.Box3();

// ...

// in the animation loop, compute the current bounding box with the world matrix
box.copy( mesh.geometry.boundingBox ).applyMatrix4( mesh.matrixWorld );

完整示例：

let W = window.innerWidth;
let H = window.innerHeight;

const renderer = new THREE.WebGLRenderer({
  antialias: true,
  alpha: true
});
document.body.appendChild(renderer.domElement);

const scene = new THREE.Scene();

const camera = new THREE.PerspectiveCamera(28, 1, 1, 1000);
camera.position.set(0, 0, 50);
camera.lookAt(scene.position);
scene.add(camera);

const light = new THREE.DirectionalLight(0xffffff, 1);
light.position.set(0, 0, -1);
camera.add(light);

let geo = new THREE.BoxBufferGeometry(5, 5, 5);
geo.computeBoundingBox();
let mat = new THREE.MeshPhongMaterial({
  color: "red"
});
const left = new THREE.Mesh(geo, mat);
left.position.set(-15, 0, 0)
scene.add(left);
const right = new THREE.Mesh(geo, mat);
right.position.set(15, 0, 0)
scene.add(right);

geo = new THREE.SphereBufferGeometry(1, 16, 16);
geo.computeBoundingBox();
mat = new THREE.MeshPhongMaterial({
  color: "yellow"
});
const ball = new THREE.Mesh(geo, mat);
scene.add(ball);

function render() {
  renderer.render(scene, camera);
}

function resize() {
  W = window.innerWidth;
  H = window.innerHeight;
  renderer.setSize(W, H);
  camera.aspect = W / H;
  camera.updateProjectionMatrix();
  render();
}

let rate = 0.1;
let goingRight = true;
let ballBox = new THREE.Box3();
let wallBox = new THREE.Box3();

function animate() {
  render();

  ball.position.x += ((goingRight) ? 1 : -1) * rate;
  ball.updateMatrix();
  ball.updateMatrixWorld(true);

  ballBox.copy(ball.geometry.boundingBox);
  ballBox.applyMatrix4(ball.matrixWorld);

  if (goingRight) {
    wallBox.copy(right.geometry.boundingBox);
    wallBox.applyMatrix4(right.matrixWorld);
    if (ballBox.intersectsBox(wallBox)) {
      goingRight = false;
    }
  } else {
    wallBox.copy(left.geometry.boundingBox);
    wallBox.applyMatrix4(left.matrixWorld);
    if (ballBox.intersectsBox(wallBox)) {
      goingRight = true;
    }
  }

  requestAnimationFrame(animate);
}

window.addEventListener("resize", resize);

resize();
requestAnimationFrame(animate);

html,
body {
  width: 100%;
  height: 100%;
  padding: 0;
  margin: 0;
  overflow: hidden;
  background: skyblue;
}

<script src="https://threejs.org/build/three.min.js"></script>