CODEWITHSUNDEEP
javascriptmaththree.js
lakers1234
lakers1234

Reputation: 125

Unable to understand the following line of code in JavaScript

I am not able to understand the execution of these lines in the code.

this.screenVector = new THREE.Vector3(0, 0, 0); this.screenVector.copy(this.position);
this.screenVector.project(camera); what does project(camera) means like what it does, and what screenVector means.

    function labelBox(Ncardinal, radius, domElement)
    {
    this.screenVector = new THREE.Vector3(0, 0, 0);
    this.position = convertlatlonToVec3(Ncardinal.lat,Ncardinal.lon).multiplyScalar(radius);
    this.box = document.createElement('div');
    a = document.createElement('a');
    a.innerHTML = Ncardinal.name;
    a.href ='http://www.google.de';
    this.box.className = "spritelabel";
    this.box.appendChild(a);

    this.domElement = domElement;
    this.domElement.appendChild(this.box);
    }

labelBox.prototype.update = function()
{
this.screenVector.copy(this.position);  
this.screenVector.project(camera);

var posx = Math.round((this.screenVector.x + 1)* this.domElement.offsetWidth/2);
var posy = Math.round((1 - this.screenVector.y)* this.domElement.offsetHeight/2);

var boundingRect = this.box.getBoundingClientRect();

//update the box overlays position
this.box.style.left = (posx - boundingRect.width) + 'px';
this.box.style.top = posy + 'px';

this.occludeLabel(this.box, this.marker);

};

Upvotes: 0

Views: 70

Answers (1)

WestLangley
WestLangley

Reputation: 104783

Vector3.project( camera ) maps a 3D point from world space to normalized device coordinate (NDC) space. See http://www.songho.ca/opengl/gl_projectionmatrix.html.

The method is required as one step in converting a 3D point from world coordinates to screen coordinates (pixels). See https://stackoverflow.com/a/27412386/1461008.

three.js r.81

Upvotes: 1

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