Question

我无法理解代码中这些行的执行情况。

this.screenVector = new THREE.Vector3（0,0,0）; this.screenVector.copy（this.position）;
this.screenVector.project（照相机）; 什么是项目（相机）意味着它做什么，以及screenVector意味着什么。

    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);

};

Answer 1

Vector3.project( camera )将3D点从世界空间映射到标准化设备坐标（NDC）空间。请参阅http://www.songho.ca/opengl/gl_projectionmatrix.html。

该方法是将3D点从世界坐标转换为屏幕坐标（像素）的一个步骤。请参阅https://stackoverflow.com/a/27412386/1461008。

three.js r.81

无法理解JavaScript中的以下代码行

1 个答案: