I've searched around for an example that matches my use case but cannot find one. I'm trying to convert screen mouse co-ordinates into 3D world co-ordinates taking into account the camera.
Solutions I've found all do ray intersection to achieve object picking.
What I am trying to do is position the center of a Three.js object at the co-ordinates that the mouse is currently "over".
My camera is at x:0, y:0, z:500 (although it will move during the simulation) and all my objects are at z = 0 with varying x and y values so I need to know the world X, Y based on assuming a z = 0 for the object that will follow the mouse position.
This question looks like a similar issue but doesn't have a solution: Getting coordinates of the mouse in relation to 3D space in THREE.js
Given the mouse position on screen with a range of "top-left = 0, 0 | bottom-right = window.innerWidth, window.innerHeight", can anyone provide a solution to move a Three.js object to the mouse co-ordinates along z = 0?
You do not need to have any objects in your scene to do this.
You already know the camera position.
Using vector.unproject( camera ) you can get a ray pointing in the direction you want.
You just need to extend that ray, from the camera position, until the z-coordinate of the tip of the ray is zero.
You can do that like so:
var vec = new THREE.Vector3(); // create once and reuse
var pos = new THREE.Vector3(); // create once and reuse
vec.set(
( event.clientX / window.innerWidth ) * 2 - 1,
- ( event.clientY / window.innerHeight ) * 2 + 1,
0.5,
);
vec.unproject( camera );
vec.sub( camera.position ).normalize();
var distance = - camera.position.z / vec.z;
pos.copy( camera.position ).add( vec.multiplyScalar( distance ) );
The variable pos is the position of the point in 3D space, "under the mouse", and in the plane z=0.
EDIT: If you need the point "under the mouse" and in the plane z = targetZ, replace the distance computation with:
var distance = ( targetZ - camera.position.z ) / vec.z;
three.js r.98