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Three.js – Create half a ring and animate it

I've created a Ring and would like to have only half of it. And after that animate it, that it builds itself up from 0 to half.
var geometry = new THREE.RingGeometry(10, 9, 32);
var material = new THREE.MeshBasicMaterial({
color: 0xffff00,
side: THREE.DoubleSide,
});
var mesh = new THREE.Mesh(geometry, material);
scene.add(mesh);
How can I archive it? I'm new to three.js.

Use thetaStart and thetaLength to animate the half-ring.
body{
overflow: hidden;
margin: 0;
}
<script type="module">
import * as THREE from "https://cdn.jsdelivr.net/npm/three#0.118.3/build/three.module.js";
var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(60, innerWidth / innerHeight, 1, 100);
camera.position.set(0, 0, 10);
var renderer = new THREE.WebGLRenderer({antialias: true});
renderer.setSize(innerWidth, innerHeight);
document.body.appendChild(renderer.domElement);
var grid = new THREE.GridHelper(10, 10);
grid.rotation.x = Math.PI * 0.5;
scene.add(grid);
var innerRadius = 1;
var outerRadius = 2;
// re-building geometry
var usualRingGeom = new THREE.RingBufferGeometry(innerRadius, outerRadius, 32, 1, 0, 1);
var usualRingMat = new THREE.MeshBasicMaterial({color: 0xffff00});
var usualRing = new THREE.Mesh(usualRingGeom, usualRingMat);
scene.add(usualRing);
var clock = new THREE.Clock();
renderer.setAnimationLoop(()=>{
let t = clock.getElapsedTime();
// re-building geometry
usualRingGeom = new THREE.RingBufferGeometry(innerRadius, outerRadius, 32, 1, 0, (Math.sin(t) * 0.5 + 0.5) * Math.PI);
usualRing.geometry.dispose();
usualRing.geometry = usualRingGeom;
renderer.render(scene, camera);
});
</script>
PS You also can achieve the same result without re-building a geometry. For that, you can bend a plane in js (changing vertices) or in shaders :)

three.js using points to make smoke effect

I want to make a smoke effect like this demo (Smoke) by using points. Now I have two problems.
At the beginning of the animation, all points get together and go up together like cloud.
the shape of the effect looks like a rectangular prism. How to make it looks like a cone (like the following picture)?
Can somebody please tell me how to fix these problems? Thanks!
let renderer, scene, camera;
let controls, stats;
// points
const particleCount = 500;
let points;
function createPoints() {
const geometry = new THREE.Geometry();
const texture = new THREE.TextureLoader().load('http://stemkoski.github.io/Three.js/images/smokeparticle.png');
let material = new THREE.PointsMaterial({
size: 15,
map: texture,
blending: THREE.AdditiveBlending,
depthWrite: false,
transparent: true,
color: 'rgb(30,30,30)'
});
const range = 10;
for (let i = 0; i < particleCount; i++) {
const x = THREE.Math.randInt(-range, range);
const y = THREE.Math.randInt(-range, range);
const z = THREE.Math.randInt(-range, range);
const point = new THREE.Vector3(x, y, z);
point.velocityX = THREE.Math.randFloat(-0.01, 0.01);
point.velocityY = THREE.Math.randFloat(0.1, 0.3);
geometry.vertices.push(point);
}
points = new THREE.Points(geometry, material);
scene.add(points);
}
function init() {
// scene
scene = new THREE.Scene();
scene.fog = new THREE.FogExp2(0x000000, 0.0008);
// camera
camera = new THREE.PerspectiveCamera( 70, window.innerWidth / window.innerHeight, 1, 1000 );
camera.position.set(0, 10, 170);
camera.lookAt(scene.position);
let axes = new THREE.AxesHelper(20);
scene.add(axes);
// renderer
renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
// OrbitControls
controls = new THREE.OrbitControls( camera, renderer.domElement );
createPoints();
document.body.appendChild(renderer.domElement);
}
function pointsAnimation() {
points.geometry.vertices.forEach(function(v) {
v.y = v.y + v.velocityY;
v.x = v.x + v.velocityX;
if (v.y >= 100) v.y = 0;
});
points.geometry.verticesNeedUpdate = true;
}
function render() {
pointsAnimation();
requestAnimationFrame(render);
controls.update();
renderer.render(scene, camera);
}
window.addEventListener('resize', function() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize(window.innerWidth, window.innerHeight);
});
init();
render();
body {
margin: 0;
overflow: hidden;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/104/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>

You could simply set velocityX depending on point x, e.g. :
point.velocityX = THREE.Math.randFloat(0.0, 0.1) * Math.sign(x);
Don't forget to reset x position :
if (v.y >= 100) {
v.x = THREE.Math.randInt(-10, 10);
v.y = 0;
}

Set 3d cube rotation origin

I have a simple 3d cube (BoxGeometry of 100, 100, 100) and I am trying to rotate it. If we call all 100x100x100 a tile - when I rotate it I can see it's overlapping the below tile.
(by changing color, now I totally understand the behaviour).
tl.to(this.cube4.rotation, 0.5, {z: -45* Math.PI/180});
[
What if I want to rotate it based on an anchor point of right bottom? So instead of overflowing inside the below tile, it will overflow that portion to above tile.
So it will look like the green example and not the red example:
The red example here is achieved by
tl.to(this.cube4.rotation, 0.5, {z: -45* Math.PI/180});
tl.to(this.cube4.position, 0.5, {x: 50 }, 0.5);
I am very new to three.js so if any terminology is wrong, please warn me

Add the ("red") cube to a THREE.Group, in that way that the rotation axis (the edge) is in the origin of the group. This means the cube has to be shifted by the half side length.
If you rotate the group object, then the cube (which is inside the group) will rotate around the edge and not around its center.
e.g.
var bbox = new THREE.Box3().setFromObject(cube);
cube.position.set(bbox.min.x, bbox.max.y, 0);
var pivot = new THREE.Group();
pivot.add(cube);
scene.add(pivot);
See also the answer to How to center a group of objects?, which uses this solution to rotate a group of objects.
(function onLoad() {
var camera, scene, renderer, orbitControls, pivot;
var rot = 0.02;
init();
animate();
function init() {
container = document.getElementById('container');
renderer = new THREE.WebGLRenderer({
antialias: true,
alpha: true
});
renderer.setPixelRatio(window.devicePixelRatio);
renderer.setSize(window.innerWidth, window.innerHeight);
renderer.shadowMap.enabled = true;
container.appendChild(renderer.domElement);
camera = new THREE.PerspectiveCamera(70, window.innerWidth / window.innerHeight, 1, 100);
camera.position.set(4, 1, 2);
//camera.lookAt( -1, 0, 0 );
loader = new THREE.TextureLoader();
loader.setCrossOrigin("");
scene = new THREE.Scene();
scene.background = new THREE.Color(0xffffff);
scene.add(camera);
window.onresize = function() {
renderer.setSize(window.innerWidth, window.innerHeight);
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
}
orbitControls = new THREE.OrbitControls(camera, container);
var ambientLight = new THREE.AmbientLight(0x404040);
scene.add(ambientLight);
var directionalLight = new THREE.DirectionalLight( 0xffffff, 0.5 );
directionalLight.position.set(1,2,-1.5);
scene.add( directionalLight );
addGridHelper();
createModel();
}
function createModel() {
var material = new THREE.MeshPhongMaterial({color:'#80f080'});
var geometry = new THREE.BoxGeometry( 1, 1, 1 );
var cube1 = new THREE.Mesh(geometry, material);
cube1.position.set(0,-0.5,-0.5);
var cube2 = new THREE.Mesh(geometry, material);
cube2.position.set(0,0.5,-0.5);
var cube3 = new THREE.Mesh(geometry, material);
cube3.position.set(0,-0.5,0.5);
var material2 = new THREE.MeshPhongMaterial({color:'#f08080'});
var cube4 = new THREE.Mesh(geometry, material2);
var bbox = new THREE.Box3().setFromObject(cube4);
cube4.position.set(bbox.min.x, bbox.max.y, 0);
pivot = new THREE.Group();
pivot.add(cube4);
pivot.position.set(-bbox.min.x, 0.5-bbox.max.y, 0.5);
scene.add(cube1);
scene.add(cube2);
scene.add(cube3);
scene.add(pivot);
}
function addGridHelper() {
var helper = new THREE.GridHelper(100, 100);
helper.material.opacity = 0.25;
helper.material.transparent = true;
scene.add(helper);
var axis = new THREE.AxesHelper(1000);
scene.add(axis);
}
function animate() {
requestAnimationFrame(animate);
orbitControls.update();
pivot.rotation.z += rot;
if (pivot.rotation.z > 0.0 || pivot.rotation.z < -Math.PI/2) rot *= -1;
render();
}
function render() {
renderer.render(scene, camera);
}
})();
<!--script src="https://threejs.org/build/three.js"></!--script-->
<script src="https://rawcdn.githack.com/mrdoob/three.js/r124/build/three.js"></script>
<script src="https://rawcdn.githack.com/mrdoob/three.js/r124/examples/js/controls/OrbitControls.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/tween.js/17.2.0/Tween.js"></script>
<div id="container"></div>

From the first image, it appears that the pivot of your red tile is at its center.
For the rotation you want, you would ideally change the pivot to the lower right of the cube. This is impossible without modifying the geometry of the cube.
BUT a simple trick is to create an empty node at that pivot point, parent your cube to that empty, and apply your rotation to the empty. (Don't forget to remove your translation, you don't need it anymore)
Here is some pseudo code, assuming your red box is centered at (0,0,0) and has a width and height of 100:
// create an empty node at desired rotation pivot
var empty = new Object3D or group
empty.position = (50, -50, 0)
// parent your cube to the empty
var cube = your box
empty.add(cube)
// you may need to change the local position of your cube to bring it back to its global position of (0,0,0)
cube.position = (-50, 50, 0)
rotate empty by 45°

I think you can get the bounds of the rotated object like this:
bounds = new THREE.Box3().setFromObject( theRedObject )
Then reposition the object.y based on its bounds.min.y
let scene, camera, controls, ambient, point, loader, renderer, container, stats;
const targetRotation = 0;
const targetRotationOnMouseDown = 0;
const mouseX = 0;
const mouseXOnMouseDown = 0;
const windowHalfX = window.innerWidth / 2;
const windowHalfY = window.innerHeight / 2;
init();
animate();
var box, b1, b2, b3;
function init() {
// Create a scene which will hold all our meshes to be rendered
scene = new THREE.Scene();
// Create and position a camera
camera = new THREE.PerspectiveCamera(
60, // Field of view
window.innerWidth / window.innerHeight, // Aspect ratio
/*window.innerWidth / -8,
window.innerWidth / 8,
window.innerHeight / 8,
window.innerHeight / -8,
*/
0.1, // Near clipping pane
1000 // Far clipping pane
);
scene.add(camera)
// Reposition the camera
camera.position.set(0, 5, 10);
// Point the camera at a given coordinate
camera.lookAt(new THREE.Vector3(0, 0, 0));
// Add orbit control
controls = new THREE.OrbitControls(camera);
controls.target.set(0, -0.5, 0);
controls.update();
// Add an ambient lights
ambient = new THREE.AmbientLight(0xffffff, 0.2);
scene.add(ambient);
// Add a point light that will cast shadows
point = new THREE.PointLight(0xffffff, 1);
point.position.set(25, 50, 25);
point.castShadow = true;
point.shadow.mapSize.width = 1024;
point.shadow.mapSize.height = 1024;
scene.add(point);
group = new THREE.Group();
group.position.y = 0;
scene.add(group);
rotationAnchor = new THREE.Object3D()
group.add(rotationAnchor);
box = new THREE.Mesh(new THREE.BoxGeometry(), new THREE.MeshStandardMaterial({
color: 'grey'
}))
b1 = box.clone();
b2 = box.clone();
b3 = box.clone();
b3.material = b3.material.clone()
b3.material.color.set('red')
group.add(box);
group.add(b1);
b1.position.y += 1
group.add(b2);
b2.position.z += 1
rotationAnchor.add(b3);
rotationAnchor.position.set(0.5, 0.5, 1.5)
b3.position.set(-.5, -.5, -.5)
// Create a renderer
renderer = new THREE.WebGLRenderer({
antialias: true
});
// Set size
renderer.setPixelRatio(window.devicePixelRatio);
renderer.setSize(window.innerWidth, window.innerHeight);
// Set color
renderer.setClearColor(0xf8a5c2);
renderer.gammaOutput = true;
// Enable shadow mapping
renderer.shadowMap.enabled = true;
renderer.shadowMap.type = THREE.PCFSoftShadowMap;
// Append to the document
container = document.createElement("div");
document.body.appendChild(container);
document.body.appendChild(renderer.domElement);
// Add resize listener
window.addEventListener("resize", onWindowResize, false);
// Enable FPS stats
stats = new Stats();
container.appendChild(stats.dom);
var gui = new dat.GUI({
height: 5 * 32 - 1
});
let params = {
'test': 4,
'bevelThickness': 1,
'bevelSize': 1.5,
'bevelSegments': 3
}
gui.add(params, 'test', 0, 10).onChange(val => {
test = val
})
}
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize(window.innerWidth, window.innerHeight);
}
function animate() {
rotationAnchor.rotation.z = (Math.cos(performance.now() * 0.001) * Math.PI * 0.25) + (Math.PI * 1.25)
requestAnimationFrame(animate);
// Re-render scene
renderer.render(scene, camera);
// Update stats
stats.update();
}
body {
overflow: hidden;
margin: 0;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/96/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>
<script src="https://threejs.org/examples/js/libs/stats.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/dat-gui/0.7.2/dat.gui.min.js"></script>

Preserve constant size regardless of perspective in Three.js

How can I preserve constant size of meshes regardless of perspective using Three.js?
Lets assume I have multiple meshes of the same size. I want them to always have the same on screen size. I also have to use perspective camera.
I have found some related answers, but seems that I miss something:
First approach is to use Euclidean distance to objects from
camera and scale them respectively every animation frame.
Three JS Keep Label Size On Zoom
I have tried to modify jsfiddle given in the answer to apply scale to meshes instead of sprites, but that doesn't work for me. The result looks as follows https://jsfiddle.net/a2ogz9vx/258/
var camera, scene, renderer, controls;
var planets = [];
var timestamp = 0;
var scaleVector = new THREE.Vector3();
init();
animate();
function init() {
scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera(90, window.innerWidth / window.innerHeight, 1, 10000);
camera.position.set(0, 100, 100);
renderer = new THREE.WebGLRenderer({
antialias: true
});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
controls = new THREE.OrbitControls(camera, renderer.domElement);
var createPlanet = function(name, radius, orbit, speed) {
var geom = new THREE.SphereGeometry(radius, 32, 16);
var mat = new THREE.MeshBasicMaterial({
color: Math.random() * 0xFFFFFF,
});
var planet = new THREE.Mesh(geom, mat);
planet.userData.orbit = orbit;
planet.userData.speed = speed;
var canvas = document.createElement('canvas');
canvas.width = 256;
canvas.height = 256;
var tex = new THREE.Texture(canvas);
tex.needsUpdate = true;
var spriteMat = new THREE.SpriteMaterial({
map: tex
});
var sprite = new THREE.Sprite(spriteMat);
planet.add(sprite);
planets.push(planet);
scene.add(planet);
};
createPlanet("One", 11, -10, 5);
createPlanet("Two", 11, 5, 5);
createPlanet("Three", 11, 10, 5);
}
function animate() {
requestAnimationFrame(animate);
planets.forEach(function(planet) {
var scaleFactor = 100;
var scale = scaleVector.subVectors(planet.position, camera.position).length() / scaleFactor;
planet.scale.set(scale, scale, scale);
var orbit = planet.userData.orbit;
var speed = planet.userData.speed;
planet.position.x = speed * orbit;
planet.position.z = speed * orbit;
});
render();
}
function render() {
renderer.render(scene, camera);
}
<script src="https://cdn.rawgit.com/mrdoob/three.js/master/build/three.min.js"></script>
<script src="https://cdn.rawgit.com/mrdoob/three.js/master/examples/js/controls/OrbitControls.js"></script>
Second approach is to use on screen width calculation. https://stackoverflow.com/a/13351534/8465699
Result also doesn't look right https://jsfiddle.net/a2ogz9vx/260/
var camera, scene, renderer, controls;
var planets = [];
var timestamp = 0;
var scaleVector = new THREE.Vector3();
init();
animate();
function init() {
scene = new THREE.Scene();
camera = new THREE.PerspectiveCamera(90, window.innerWidth / window.innerHeight, 1, 10000);
camera.position.set(0, 100, 100);
renderer = new THREE.WebGLRenderer({
antialias: true
});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
controls = new THREE.OrbitControls(camera, renderer.domElement);
var createPlanet = function(name, radius, orbit, speed) {
var geom = new THREE.SphereGeometry(radius, 32, 16);
var mat = new THREE.MeshBasicMaterial({
color: Math.random() * 0xFFFFFF,
});
var planet = new THREE.Mesh(geom, mat);
planet.userData.orbit = orbit;
planet.userData.speed = speed;
var canvas = document.createElement('canvas');
canvas.width = 256;
canvas.height = 256;
var tex = new THREE.Texture(canvas);
tex.needsUpdate = true;
var spriteMat = new THREE.SpriteMaterial({
map: tex
});
var sprite = new THREE.Sprite(spriteMat);
planet.add(sprite);
planets.push(planet);
scene.add(planet);
};
createPlanet("One", 11, -10, 5);
createPlanet("Two", 11, 0, 5);
createPlanet("Three", 11, 10, 5);
}
function animate() {
requestAnimationFrame(animate);
planets.forEach(function(planet) {
const dist = planet.position.distanceTo(camera.position);
const vFOV = THREE.Math.degToRad(camera.fov);
const size = 2 * Math.tan(vFOV / 2) * dist;
const scaleFactor = 130;
const scale = size / scaleFactor;
planet.scale.set(scale, scale, scale);
var orbit = planet.userData.orbit;
var speed = planet.userData.speed;
planet.position.x = speed * orbit;
planet.position.z = speed * orbit;
});
render();
}
function render() {
renderer.render(scene, camera);
}
<script src="https://cdn.rawgit.com/mrdoob/three.js/master/build/three.min.js"></script>
<script src="https://cdn.rawgit.com/mrdoob/three.js/master/examples/js/controls/OrbitControls.js"></script>
Any suggestions how to fix the code or other approaches are welcome!

Adding number of cubes in three.js

I am trying to add a number of spheres in the following example. Initially it had only three cubes, but I need to add some 10 spheres that would be equidistant from each other and would be rotating in different speeds.
My Try
var parent, renderer, scene, camera, controls;
init();
animate();
function init()
{
// renderer
renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
// scene
scene = new THREE.Scene();
// camera
camera = new THREE.PerspectiveCamera(40, window.innerWidth / window.innerHeight, 1, 100);
camera.position.set(20, 20, 20);
// controls
controls = new THREE.OrbitControls(camera);
controls.minDistance = 10;
controls.maxDistance = 50;
// axes
scene.add(new THREE.AxisHelper(20));
// geometry
var geometry = new THREE.SphereGeometry(0.3, 50, 50, 0, Math.PI * 2, 0, Math.PI * 2)
// material
var material = new THREE.MeshBasicMaterial({
color: 0xffffff,
wireframe: true
});
// parent
parent = new THREE.Object3D();
scene.add(parent);
// pivots
var pivot1 = new THREE.Object3D();
var pivot2 = new THREE.Object3D();
var pivot3 = new THREE.Object3D();
var pivot4 = new THREE.Object3D();
pivot1.rotation.z = 0;
pivot2.rotation.z = 2 * Math.PI / 3;
pivot3.rotation.z = 4 * Math.PI / 3;
pivot4.rotation.z = 6 * Math.PI / 3;
parent.add(pivot1);
parent.add(pivot2);
parent.add(pivot3);
parent.add(pivot4);
// mesh
var mesh1 = new THREE.Mesh(geometry, material);
var mesh2 = new THREE.Mesh(geometry, material);
var mesh3 = new THREE.Mesh(geometry, material);
var mesh4 = new THREE.Mesh(geometry, material);
mesh1.position.y = 5;
mesh2.position.y = 5;
mesh3.position.y = 5;
mesh4.position.y = 5;
pivot1.add(mesh1);
pivot2.add(mesh2);
pivot3.add(mesh3);
pivot4.add(mesh4);
}
function animate()
{
requestAnimationFrame(animate);
parent.rotation.z += 0.01;
controls.update();
renderer.render(scene, camera);
}
Why am I not able to add more than 3 spheres into the scene? I tried to add the fourth sphere but it did not work. How can speed be accounted for here? That is: can I specify different speeds for some spheres?

Missing 4th Sphere
You specify:
pivot1.rotation.z = 0;
pivot2.rotation.z = 2 * Math.PI / 3;
pivot3.rotation.z = 4 * Math.PI / 3;
pivot4.rotation.z = 6 * Math.PI / 3;
6 * Math.PI / 3 = 2 * Math.PI
Note, three.js uses radians, therefore 2 * PI is 0 (a full revolution is the same place as no rotation.
So pivot1 and pivot4 have the same effective rotation and your 2 sphere end up in the same place in space.
Speed
You currently handle speed by mutating the z rotation on every frame.
parent.rotation.z += 0.01;
This obviously works just fine for a demo. You can speed it up by moving more per frame (or getting more frames, ie better machine or other upgrades)
parent.rotation.z += 0.04;
Now it rotates at 4 times the speed!
More Spheres
Once you get past working with counts larger than your number of fingers on a hand, I recommend getting generic with arrays. Instead of listing out pivot1, pivot2, pivot3, . . . pivot0451, generate this with a loop. (Functionally you could use ranges if you prefer).
First, we declare how many spheres to make. Then divide up the circle (2 * Math.PI radians to go around). Then for ever sphere, make a pivot. Then, for every pivot, add a mesh. And you're done.
var numberOfSpheres = 10;
var radiansPerSphere = 2 * Math.PI / numberOfSpheres;
// pivots
var pivots = [];
for (var i = 0; i < numberOfSpheres; i++) {
var pivot = new THREE.Object3D();
pivot.rotation.z = i * radiansPerSphere;
parent.add(pivot);
pivots.push(pivot);
}
var meshes = pivots.map((pivot) => {
var mesh = new THREE.Mesh(geometry, material);
mesh.position.y = 5;
pivot.add(mesh)
return mesh;
});
I implemented this at this codepen.io
Happy coding.