THREE.js Ray Intersect fails by adding div

Question

My Three.js script runs fine when there is only one target div on the page (which holds renderer.domElement). As soon as I add another div with fixed height and width above the target div, ray.intersectObjects returns null. I doubt that the vector that I am creating for ray is causing the problem. Here is the code.

var vector = new THREE.Vector3( ( event.clientX / divWidth ) * 2 - 1, -( event.clientY / divHeight ) * 2 + 1, 0.5 );

projector.unprojectVector( vector, camera );

var ray = new THREE.Ray( camera.position, vector.subSelf( camera.position ).normalize() );

var intersects = ray.intersectObjects( myObjects, true );

Any ideas on how I can solve this.

EDIT: it is now THREE.Raycaster (three.js r.56)

WestLangley · Accepted Answer · 2023-02-04T21:03:35.437

The short answer is you have to take into consideration the offset of the canvas.

The long answer depends on how your code is written, so I'll give you two answers, which should cover the bases.

Assume your HTML is something like this:

#canvas {
    width: 200px;
    height: 200px;
    margin: 100px;
    padding: 0px;
    position: static; /* fixed or static */
    top: 100px;
    left: 100px;
}

<body>
    <div id="canvas">
</body>

Your JS is something like this:

var CANVAS_WIDTH = 200,
CANVAS_HEIGHT = 200;

var container = document.getElementById( 'canvas' );
document.body.appendChild( container );

renderer = new THREE.WebGLRenderer();
renderer.setPixelRatio( window.devicePixelRatio );
renderer.setSize( CANVAS_WIDTH, CANVAS_HEIGHT );
container.appendChild( renderer.domElement );

Method 1 For the following method to work correctly, set the canvas position static; margin > 0 and padding > 0 are OK

mouse.x = ( ( event.clientX - renderer.domElement.offsetLeft ) / renderer.domElement.clientWidth ) * 2 - 1;
mouse.y = - ( ( event.clientY - renderer.domElement.offsetTop ) / renderer.domElement.clientHeight ) * 2 + 1;

Method 2 For this alternate method, set the canvas position fixed; set top > 0, set left > 0; padding must be 0; margin > 0 is OK

mouse.x = ( ( event.clientX - container.offsetLeft ) / container.clientWidth ) * 2 - 1;
mouse.y = - ( ( event.clientY - container.offsetTop ) / container.clientHeight ) * 2 + 1;

Here is a Fiddle if you want to experiment: https://jsfiddle.net/uf4c0ws9/

EDIT: Fiddle updated to three.js r.150

You may need to multiply the numerator on the mouse x and y calculations by renderer.devicePixelRatio for the devices (retina displays etc.) where that value is not equal to one. — Charlotte, Jan 09 '15 at 17:55

LF00 · Answer 2 · 2019-05-29T00:48:59.520

enent.clientX is the client window offset, so to calculate the mouse position we also have to use the renderer element client window offset. Use the element.getBoundingClientRect() to get the element rect offset the window.

var rect = renderer.domElement.getBoundingClientRect();
mouse.x = ( ( event.clientX - rect.left ) / ( rect.width - rect.left ) ) * 2 - 1;
mouse.y = - ( ( event.clientY - rect.top ) / ( rect.bottom - rect.top) ) * 2 + 1;

<html>
<head>
<script src="http://threejs.org/build/three.min.js"></script>

    <link rel="stylesheet" href="http://libs.baidu.com/bootstrap/3.0.3/css/bootstrap.min.css" />


<style>
body {
    font-family: Monospace;
    background-color: #fff;
    margin: 0px;
    overflow: hidden;
}

#canvas {
    background-color: #000;
    width: 200px;
    height: 200px;
    border: 1px solid black;
    margin: 10px;
    padding: 0px;
    top: 10px;
    left: 100px;
}

.border {
    padding:10px; 
    margin:10px;
}

</style>
</head>
<body>
<div class="border">
 <div class="border">
  <div id="canvas"></div>
 </div>
</div>
<script>
// Three.js ray.intersects with offset canvas

var container, camera, scene, renderer, mesh,

    objects = [],
    
    count = 0,

    CANVAS_WIDTH = 200,
    CANVAS_HEIGHT = 200;

// info
info = document.createElement( 'div' );
info.style.position = 'absolute';
info.style.top = '30px';
info.style.width = '100%';
info.style.textAlign = 'center';
info.style.color = '#f00';
info.style.backgroundColor = 'transparent';
info.style.zIndex = '1';
info.style.fontFamily = 'Monospace';
info.innerHTML = 'INTERSECT Count: ' + count;
info.style.userSelect = "none";
info.style.webkitUserSelect = "none";
info.style.MozUserSelect = "none";
document.body.appendChild( info );

container = document.getElementById( 'canvas' );

renderer = new THREE.WebGLRenderer();
renderer.setSize( CANVAS_WIDTH, CANVAS_HEIGHT );
container.appendChild( renderer.domElement );

scene = new THREE.Scene();

camera = new THREE.PerspectiveCamera( 45, CANVAS_WIDTH / CANVAS_HEIGHT, 1, 1000 );
camera.position.y = 250;
camera.position.z = 500;
camera.lookAt( scene.position );
scene.add( camera );

scene.add( new THREE.AmbientLight( 0x222222 ) );

var light = new THREE.PointLight( 0xffffff, 1 );
camera.add( light );

mesh = new THREE.Mesh( 
 new THREE.BoxGeometry( 200, 200, 200, 1, 1, 1 ), 
 new THREE.MeshPhongMaterial( { color : 0x0080ff } 
) );
scene.add( mesh );
objects.push( mesh );

// find intersections
var raycaster = new THREE.Raycaster();
var mouse = new THREE.Vector2();

// mouse listener
document.addEventListener( 'mousedown', function( event ) {
    
 var rect = renderer.domElement.getBoundingClientRect();
mouse.x = ( ( event.clientX - rect.left ) / ( rect.width - rect.left ) ) * 2 - 1;
mouse.y = - ( ( event.clientY - rect.top ) / ( rect.bottom - rect.top) ) * 2 + 1;
  
 raycaster.setFromCamera( mouse, camera );

    intersects = raycaster.intersectObjects( objects );

    if ( intersects.length > 0 ) {
        
        info.innerHTML = 'INTERSECT Count: ' + ++count;
        
    }

}, false );

function render() {

    mesh.rotation.y += 0.01;
    
    renderer.render( scene, camera );

}

(function animate() {

    requestAnimationFrame( animate );

    render();

})();

</script>
</body>
</html>

I got good results by modifying mouse.x denominator `mouse.x = ( ( event.clientX - rect.left ) / ( rect.right - rect.left ) ) * 2 - 1;` — beepscore, Sep 15 '17 at 02:15
@beepscore your comment is correct and helped me a lot, thanks — PeterB, Apr 21 '18 at 18:50

score 4 · Answer 3 · answered Feb 25 '15 at 11:04

WestLangley, thanks a lot for your explanation. It was really helpful as usual.

In my case, I had my chart in a div absolutely positioned, so I had to do this:

    var offset = $('.rightBlock').offset();


    mouse.x = ( ( event.clientX - offset.left ) / renderer.domElement.width ) * 2 - 1;
    mouse.y = - ( ( event.clientY - offset.top ) / renderer.domElement.height ) * 2 + 1;

Where rightBlock is my container, that uses only 70% of the screen.

You inspired me and help me solving this problematic issue! Thanks a lot.

well, this doesn't work when you zoom out the geometry, there will be an offset, do you know how to fix this? — Displee, Aug 20 '17 at 13:52

score 0 · Answer 4 · answered Mar 20 '23 at 07:49

I had a div (slider) with position absolute and a canvas nested inside.

<div class='slider'><div id="canvas-container"></div></div>

const canvasContainer: HTMLElement = document.getElementById('canvas-container');

this.renderer.setSize(canvasContainer.clientWidth, canvasContainer.clientHeight);
canvasContainer.appendChild(this.renderer.domElement);


const renderer = this.renderer.domElement.getBoundingClientRect();
this.mouse.x = ( ( e.clientX - renderer.left ) / ( renderer.right - renderer.left ) ) * 2 - 1;
this.mouse.y = - ( ( e.clientY - renderer.top ) / ( renderer.bottom - renderer.top) ) * 2 + 1;

this.raycaster.intersectObject(this.model, true);

THREE.js Ray Intersect fails by adding div

4 Answers4

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