我正在创建粒子并使用three.js随机定位它们:
for( var i = 0; i < particleCount; i++ ){
var pX = Math.random() * 100-50;
var pY =Math.random() * 100-50;
var pZ = Math.random() * 100-50;
particle = new THREE.Vector3(pX,pY,pZ);
particle.velocity = new THREE.Vector3(Math.random(), Math.random(), pZ);
particles.vertices.push(particle);
}
然后在我的requestAnimationFrame更新函数中,我正在移动粒子:
for (var i = 0; i < particleCount; i++) {
var particle = particles.vertices[i];
particle.y += particle.velocity.y*speed;
particle.x += particle.velocity.x*speed;
}
如何为运动引入一些限制?即当粒子到达屏幕的边缘时,我想&#34;反弹&#34;他们回来了。
答案 0 :(得分:1)
为每个粒子提供方向和速度更好。方向始终是标准化的THREE.Vector3()
。
然后你的粒子的代码将是这样的:
var particles = [];
var particleCount = 100;
var sizeX = 300;
var sizeY = 200;
var sizeZ = 100;
for (var i = 0; i < particleCount; i++) {
var pX = Math.random() * sizeX - sizeX / 2;
var pY = Math.random() * sizeY - sizeY / 2;
var pZ = Math.random() * sizeZ - sizeZ / 2;
particle = new THREE.Vector3(pX, pY, pZ);
particle.direction = new THREE.Vector3(Math.random() - .5, Math.random() - .5, 0).normalize(); // a normalized vector with random values for x,y
particle.velocity = Math.random() * 50; // speed is 50 units per second
particles.push(particle);
}
假设您使用THREE.Points()
:
var geometry = new THREE.Geometry();
geometry.vertices = particles;
var points = new THREE.Points(geometry, new THREE.PointsMaterial({
size: 5,
color: "red"
}));
scene.add(points);
要设置正确的速度(我们每秒50个单位),我们需要THREE.Clock()
及其.getDelta()
方法:
var clock = new THREE.Clock();
var shift = new THREE.Vector3(); //we will re-use it in the animation loop
var delta = 0; // we will re-use it in the animation loop
在动画循环中,我们将执行此操作:
delta = clock.getDelta(); // get period between frames (in seconds)
particles.forEach(function(p) {
if (p.x > sizeX / 2 || p.x < -sizeX / 2) { // it's also can be like if (Math.abs(p.x > sizeX / 2))
p.direction.x = -p.direction.x;
}
if (p.y > sizeY / 2 || p.y < -sizeY / 2) {
p.direction.y = -p.direction.y;
}
if (p.z > sizeZ / 2 || p.z < -sizeZ / 2) {
p.direction.z = -p.direction.z;
}
p.add(shift.copy(p.direction).multiplyScalar(p.velocity * delta)); // here we re-use the `shift` vector
})
points.geometry.verticesNeedUpdate = true; // important, if you won't set it to true you won't get your particles moving
这就是它。
jsfiddle示例
PS如果你想使用BufferGeometry
,那么你可以参考这个非常好的SO answer