ThreeJS. How to implement ZoomALL and make sure a given box fills the canvas area?

Question

I am looking for a function to ensure that a given box or sphere will be visible in a WebGL canvas, and that it will fit the canvas area. I am using a perspective camera and the camera already points to the middle of the object. I understand that this could be achieved by changing the FOV angle or by moving the camera along the view axis.

Any idea how this could be achieved with ThreeJS ?

This question has been answered before: [here](http://stackoverflow.com/questions/15331358/three-js-get-object-size-with-respect-to-camera-and-object-position-on-screen/15331885#15331885) and [here](http://stackoverflow.com/questions/13350875/three-js-width-of-view/13351534#13351534) — WestLangley, Apr 02 '13 at 12:49
The link that you provide explain how to calculate the zoom factor. In my case I also want to focus the camera to make a given box visible , without changing the camera orientation. — Etienne, May 23 '13 at 06:10

Etienne · Answer 1 · 2019-03-14T19:17:31.343

This is how I finally implemented it:

var camera = new THREE.PerspectiveCamera(35,1,1, 100000);
var controls = new THREE.TrackballControls( me.camera , container);
[...]


/**
 * point the current camera to the center
 * of the graphical object (zoom factor is not affected)
 *
 * the camera is moved in its  x,z plane so that the orientation 
 * is not affected either
 */
function pointCameraTo (node) {

    var me = this;

    // Refocus camera to the center of the new object
    var COG = shapeCenterOfGravity(node);

    var v = new THREE.Vector3();
    v.subVectors(COG,me.controls.target);

    camera.position.addVectors(camera.position,v);

    // retrieve camera orientation and pass it to trackball  
    camera.lookAt(COG);
    controls.target.set( COG.x,COG.y,COG.z );  

};

/**
 *  Zoom to object
 */
function zoomObject (node) {

   var me = this; 

   var bbox = boundingBox(node);
   if (bbox.empty()) {
       return;
   }
   var COG =  bbox.center();

   pointCameraTo(node);

   var sphereSize = bbox.size().length() * 0.5;
   var distToCenter = sphereSize/Math.sin( Math.PI / 180.0 * me.camera.fov * 0.5);

   // move the camera backward 

   var target = controls.target;
   var vec = new THREE.Vector3();
   vec.subVectors( camera.position, target );
   vec.setLength( distToCenter );
   camera.position.addVectors(  vec , target );
   camera.updateProjectionMatrix();
   render3D();
};

An example of this can be seen in https://github.com/OpenWebCAD/node-occ-geomview/blob/master/client/geom_view.js

score 0 · Answer 2 · edited Jul 05 '17 at 16:05

Here is how I did it { Using TrackBall to Zoomin/out pan etc }

function init(){
......
......
controls = new THREE.TrackballControls(camera);

controls.rotateSpeed = 1.0;
controls.zoomSpeed = 1.2;
controls.panSpeed = 0.8;

controls.noZoom = false;
controls.noPan = false;

controls.staticMoving = true;
controls.dynamicDampingFactor = 0.3;

controls.keys = [65, 83, 68];

controls.addEventListener('change', render);

.....
.....
render(scene, camera);
animate();
}
function render() 

{
    renderer.render(scene, camera);
    //stats.update();
}

function animate() {
    requestAnimationFrame(animate);
    controls.update();
}

ThreeJS. How to implement ZoomALL and make sure a given box fills the canvas area?

2 Answers2

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