Move camera backwards and forwards in Three js

Question

How would you move a camera backwards and forwards from a fixed point along the trajectory that it is facing?

I know there are several control scripts that do this but I need to do something custom and I'm not able to break down their code to figure how to isolate the above behaviour.

I've seen this answer which I think addresses the question and have come up with this code:

cameraPosition = camera.position
cameraRotation = new THREE.Vector3(camera.rotation._x, camera.rotation._y, camera.rotation._z)
newCamera = new THREE.Vector3().addVectors(cameraPosition, cameraRotation)
camera.position.set(newCamera.x, newCamera.y, newCamera.z)
camera.updateProjectionMatrix()

But this seems to move the camera in a circle rather than backwards and forwards.

Any help would be much appreciated. Thank you!

to move camera backwards or forwards you just need to change z component of the camera position, adding to it some delta vector. — ampawd, Jun 30 '16 at 11:03
See http://stackoverflow.com/questions/38052621/moving-the-camera-in-the-direction-its-facing-with-threejs/38057216#38057216 — WestLangley, Jul 01 '16 at 00:31
@WestLangley You're right. Sorry I didn't check that earlier. I assumed that `camera.translateZ( x )` would be the same as `camera.position.z += x;`. But I was wrong. Thank you! — bravokiloecho, Jul 12 '16 at 12:45

score 18 · Accepted Answer · answered Jul 13 '16 at 01:20

18

To move the camera forward or backward the direction it is facing, use

camera.translateZ( - distance );

or

camera.translateZ( distance );

three.js r.78

answered Jul 13 '16 at 01:20

WestLangley

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4

and not surprisingly `camera.translateX` and `camera.translateY` do camera relative translations sideways and up and down respectively. – Symbolic Jun 24 '17 at 11:04
But this makes the camera also go downwards instead of only forward. – Displee Dec 23 '22 at 10:41

Stubbies · Answer 2 · 2016-06-30T12:19:47.630

Here's how you do it by updating the camera.position.z. Use the W=forward, S=backward

var camera, scene, renderer, geometry, material, mesh;

init();
animate();

function init() {

    scene = new THREE.Scene();

    camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 1, 10000);
    camera.position.z = 500;
    scene.add(camera);

    geometry = new THREE.CubeGeometry(200, 200, 200);
    material = new THREE.MeshNormalMaterial();

    mesh = new THREE.Mesh(geometry, material);
    scene.add(mesh);

    renderer = new THREE.WebGLRenderer( { antialias: true } );
    renderer.setSize(window.innerWidth, window.innerHeight);
    
    document.body.appendChild(renderer.domElement);
    document.body.addEventListener( 'keydown', onKeyDown, false );

}

function animate() {

    requestAnimationFrame(animate);
    render();

}

function render() {
    mesh.rotation.x += 0.01;
    mesh.rotation.y += 0.02;

    renderer.render(scene, camera);
}

function onKeyDown(){
switch( event.keyCode ) {
   case 83: // up
   camera.position.z += 50;
   break;
   case 87: // down
   camera.position.z -= 50;
   break;
}
   
}

<script src="https://ajax.googleapis.com/ajax/libs/threejs/r76/three.min.js"></script>

Thanks for the great reply. I guess I should have been more specific though... In my scene the camera has x, y, & z position's set and is pointing at the centre of the scene. I was hoping to move the camera along the trajectory it was facing. I've modified your code above to demonstrate: https://jsfiddle.net/a9rhtLnk/ - Now the camera moves over the cube, but I was trying to make it move *into* the cube — bravokiloecho, Jul 12 '16 at 10:09

Move camera backwards and forwards in Three js

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