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Three.js move camera distance to object by z

I'm rotating a PerspectiveCamera with orbitControls around an object. Now I want to move the camera closer to the object but keep the actual rotation.
My coordinate to set the distance to the objects are output as [0,0,100].
But my CameraPosition is [-500, 96, 1772]. How can I keep the "rotation" but move the camera closer to the object to a distance of 100.
Do I need to use getAzimuthalAngle() or getPolarAngle()?

For example, like this, if you object is not in the center of a scene:
camera.position.sub(obj.position).setLength(100).add(obj.position);
If the object is in the center:
camera.position.setLength(100);
var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(60, window.innerWidth / window.innerHeight, 1, 1000);
camera.position.set(25, 0, 100);
var renderer = new THREE.WebGLRenderer({
antialias: true
});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
var controls = new THREE.OrbitControls(camera, renderer.domElement);
scene.add(new THREE.GridHelper(100, 100));
var obj = new THREE.Mesh(new THREE.CubeGeometry(10, 10, 10), new THREE.MeshBasicMaterial({
color: "red",
wireframe: true
}));
obj.position.set(25, 0, 0);
scene.add(obj);
controls.target.copy(obj.position);
controls.update();
stepCloser.addEventListener("click", onClick, false);
function onClick() {
camera.position.sub(obj.position).setLength(100).add(obj.position);
}
render();
function render() {
requestAnimationFrame(render);
renderer.render(scene, camera);
}
body {
overflow: hidden;
margin: 0;
}
<script src="https://threejs.org/build/three.min.js"></script>
<script src="https://threejs.org/examples/js/controls/OrbitControls.js"></script>
<button id="stepCloser" style="position: absolute;">
100 units to the object
</button>

this will work. I was trying to load the GLTF model through this code snippet.
loader.load('./demo-models/model-1/scene.gltf', function (gltf) {
gltf.position.x -= 60
scene.add(gltf.scene);
});
But that didn't work out. So after debugging for a while, I realized I could play around with some parameters of the Perspective Camera. Well initially the first argument was 75 units which made my object way too far from the screen, I had to zoom in until I could get a clear view. Some code tweaks, it works the best when I set it to 1.
var camera = new THREE.PerspectiveCamera(1, window.innerWidth / window.innerHeight, 0.1, 1000);

Three JS Animation Screen Blank

I'm new to three js and webgl. I have a complicated solar system I'm building and it all works great until I want to animate anything. Here is a very stripped down version to show the problem (with sun in low res). If I add the line sun.rotate.y += 1; it wont load or run anything at all. I have looked around a lot and can't figure out why. I'm sure it is something stupid I'm missing. Thanks for any help.
<script>
// SETUP SCENE
var camera, controls, scene, renderer;
var container
init();
animate();
function init() {
camera = new THREE.PerspectiveCamera( 60, window.innerWidth / window.innerHeight, 1, 90000 );
camera.position.z = 100;
controls = new THREE.TrackballControls( camera );
controls.rotateSpeed = 1.0;
controls.zoomSpeed = .2;
controls.panSpeed = 0.8;
controls.noZoom = false;
controls.noPan = true;
controls.staticMoving = false;
controls.dynamicDampingFactor = 0.3;
controls.keys = [ 65, 83, 68 ];
controls.addEventListener( 'change', render );
scene = new THREE.Scene();
// ADD THE SUN PHYSICAL LOCATION
var geometry = new THREE.SphereGeometry(5, 3, 3, 0, Math.PI * 2, 0, Math.PI * 2);
var material = new THREE.MeshBasicMaterial({color: "Yellow"});
var sun = new THREE.Mesh(geometry, material);
scene.add(sun);
//RENDER
renderer = new THREE.WebGLRenderer( { antialias: false } );
renderer.setPixelRatio( window.devicePixelRatio );
renderer.setSize( window.innerWidth, window.innerHeight );
container = document.getElementById( 'container' );
container.appendChild( renderer.domElement );
window.addEventListener( 'resize', onWindowResize, false );
render();
animate();
}
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize( window.innerWidth, window.innerHeight );
controls.handleResize();
render();
}
function animate() {
requestAnimationFrame( animate );
controls.update();
render();
}
function render() {
sun.rotate.y +=1; // Problem animating?
renderer.render( scene, camera );
}
</script>

You need to define sun as a global variable because currently it is not visible in the render() scope.
Also, I think to rotate a mesh you call "rotateX(), rotateY() or rotateZ()" so it is sun.rotateY(0.01)
Edit: I realized you can rotate the mesh by modifying its rotation rather than its rotate property.

You have a scope issue ( well it's complicated depending on what you are using es6 or es5), these are the offending bits:
Declare your global(or not Js will add it) to the global space :
var container, sun;
And refer to it inside the init function:
this.sun = new THREE.Mesh(geometry, material);
Working Pen:
Scope Issue in Three.js
Also, TrackballControls is not part of Three.js, you have to import it, check the pen.
Also, Also,for the rotation you might want to use:
sun.rotation.y += 0.003;

Three.js add a rotating camera

jsfiddle: http://jsfiddle.net/VsWb9/2151/
After a reading a few articles i am at a loss.
Rotate camera around object with Three.js
Below is simple code for a cube rotating with a floor. This should hopefully be a simple example to follow.
I am trying to add a camera so on click and drag it rotates around the scene. Similar to this http://threejs.org/examples/#misc_controls_trackball
For anyone with the same quesiton lets get you to my point below:
Download three.js here:
http://threejs.org/
You need to have something call orbit controls in your js folder. You will find a link to orbitcontrols to download here:
https://dl.dropboxusercontent.com/u/3587259/Code/Threejs/OrbitControls.js
Copy this and put it in your site folder.
You then need to link to orbit control and three.js it in your html. Like the below:
<script src="js/OrbitControls.js"></script>
<script src="js/three.min.js"></script>
Then see below for a simple wireframe cube with a floor.
var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(50, window.innerWidth/window.innerHeight, 0.1, 1000);
var axisHelper = new THREE.AxisHelper( 5 );
var renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
//This breaks it?
//controls = new THREE.OrbitControls( camera, renderer.domElement );
var geometry = new THREE.CubeGeometry(2,1,1);
var material = new THREE.MeshBasicMaterial({wireframe: true});
var cube = new THREE.Mesh(geometry, material);
scene.add(cube);
var floorMaterial = new THREE.MeshBasicMaterial( {wireframe: true} );
var floorGeometry = new THREE.PlaneGeometry(1000, 1000, 10, 10);
var floor = new THREE.Mesh(floorGeometry, floorMaterial);
floor.position.y = -50.0;
floor.rotation.x = Math.PI / 2;
scene.add(floor);
camera.position.z = 3;
var render = function () {
requestAnimationFrame(render);
cube.rotation.z += 0.005;
cube.rotation.x += 0.005;
renderer.render(scene, camera);
};
render();

Understanding Sprite distance using Raycast in three js

I'm adding sprites in a 3d scene using three.js and I want to know distance between the camera and sprite when I click on screen. So I use a Raycater.
But if I click on the sprite, the distance property of intersection object is always "wrong" (someting like 0.3), or maybe I don't know how to read and understand the result. I thought "distance" value of intersection is the distance from camera to sprite (so, in my case something like 5).
Here is a shortened version of my code :
var scene = new THREE.Scene();
var camera = new THREE.PerspectiveCamera(75, window.innerWidth/window.innerHeight, 0.1, 1000);
var renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
var sprite = new THREE.Sprite(new THREE.SpriteMaterial({color: 0x00ff00}));
scene.add(sprite);
camera.position.z = 5;
var render = function () {
requestAnimationFrame(render);
renderer.render(scene, camera);
};
render();
window.addEventListener('mousedown', function (e) {
if (e.target == renderer.domElement) {
var vector = new THREE.Vector3((e.clientX / window.innerWidth) * 2 - 1, -(e.clientY / window.innerHeight) * 2 + 1, 0.5);
var projector = new THREE.Projector();
projector.unprojectVector(vector, camera);
var raycaster = new THREE.Raycaster(camera.position, vector.sub(camera.position).normalize());
var intersects = raycaster.intersectObjects([sprite]);
console.log(intersects[0]);
}
}, false);
You can see it in action here : http://jsfiddle.net/pWr57/
So how can I have the distance form camera to a sprite ?
three.js r66

Do this, instead
console.log( raycaster.ray.origin.distanceTo( intersects[0].point ) );
Tip: Read the source code, Raycaster.js, so you know what it is doing. It is currently returning the perpendicular distance from the sprite center to the ray.
In this case, I agree that it would be better to return the distance from the camera.
three.js r.66

Three.js wont render on canvas

I loaded the script in index.html but when I open the page it shows the rendered but nothing inside, nothing renderer, I can't find the problem
Here is the code of external .js:
var wdt = $('.design').width();
var hgh = $('.design').height();
var scene = new THREE.Scene();
var camera = new THREE.Camera(75, wdt/hgh, 0.1, 1000);
var renderer = new THREE.WebGLRenderer({ alpha: true });
renderer.setSize(wdt, hgh);
document.getElementById('designer').appendChild(renderer.domElement);
var geometry = new THREE.CubeGeometry(1,1,1);
var material = new THREE.MeshBasicMaterial({color: 0x00ff00});
var cube = new THREE.Mesh(geometry, material);
scene.add(cube);
camera.position.z = 5;
var render = function () {
requestAnimationFrame(render);
cube.rotation.x += 0.1;
cube.rotation.y += 0.1;
renderer.render(scene, camera);
};
render();
Can anybody help please?

Camera issues
Here's a jsfiddle of a working version.
Camera in Three.js is abstract, so I picked the common one to construct:
var camera = new THREE.PerspectiveCamera (75, wdt / hgh, 0.1, 1000);
The camera's viewpoint doesn't line up by default, so explicit calls eliminate confusion:
camera.lookAt(cube.position);
And adding the camera to the scene:
scene.add(camera);