Converting World coordinates to Screen coordinates in Three.js using Projection

Solution 1:

Try with this:

var width = 640, height = 480;
var widthHalf = width / 2, heightHalf = height / 2;

var vector = new THREE.Vector3();
var projector = new THREE.Projector();
projector.projectVector( vector.setFromMatrixPosition( object.matrixWorld ), camera );

vector.x = ( vector.x * widthHalf ) + widthHalf;
vector.y = - ( vector.y * heightHalf ) + heightHalf;

Solution 2:

For modern Three.js (r75), a vector can be projected onto the screen with:

var width = window.innerWidth, height = window.innerHeight;
var widthHalf = width / 2, heightHalf = height / 2;

var pos = object.position.clone();
pos.project(camera);
pos.x = ( pos.x * widthHalf ) + widthHalf;
pos.y = - ( pos.y * heightHalf ) + heightHalf;

Solution 3:

For everyone getting deprecated or warnings logs, the accepted answer is for older Three.js versions. Now it's even easier with:

let pos = new THREE.Vector3();
pos = pos.setFromMatrixPosition(object.matrixWorld);
pos.project(camera);

let widthHalf = canvasWidth / 2;
let heightHalf = canvasHeight / 2;

pos.x = (pos.x * widthHalf) + widthHalf;
pos.y = - (pos.y * heightHalf) + heightHalf;
pos.z = 0;

console.log(pos);