javascript - 三JS : Mesh becomes invisible when inside another mesh

Question

我花了几个小时试图弄清楚为什么我看不到立方体内的文本，而且我不明白为什么它不起作用。

有两个网格，其中一个在另一个网格内部，但不可见。

当我注释将立方体网格添加到我的组中的行时，会出现文本(第 34 行)。如果我从其 Material 中删除“transparent: true”，我可以看到文本，但会出现背景(第 52 行)。

文本作为 Canvas 纹理添加，这是我发现动态添加二维文本的最简单方法。

我只想在我的立方体中添加一些白色文本，而没有任何背景颜色。

我看到了这个问题，但看起来它与我的问题无关:THREE.JS: Seeing geometry when inside mesh

var renderer, scene, camera, cubeGroup;
var rotationX = 0;
var rotationY = 0;
var percentX, percentY;
var container = document.getElementById('container');

init();
animate();

function init(){
    renderer = new THREE.WebGLRenderer({alpha: true});
    renderer.setSize(window.innerWidth, window.innerHeight);
    renderer.setClearColor( 0x000000, 1);
    document.getElementById('container').appendChild(renderer.domElement);

    scene = new THREE.Scene();

    camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 1, 10000);
    camera.position.set(0, 0, 1000);
    scene.add(camera);
    
    // group
    cubeGroup = new THREE.Group();
    
    // cube
    var geometry = new THREE.BoxGeometry(200, 200, 200);
    var material = new THREE.MeshPhongMaterial({ 
      color: 0x11111f, 
      side: THREE.DoubleSide, 
      opacity: .5,
      transparent: true 
    });
    var mesh = new THREE.Mesh(geometry, material);
    cubeGroup.add(mesh); // Comment this and the text appears with transparency
    
    var ambientLight = new THREE.AmbientLight(0x999999, 0.8);
    scene.add(ambientLight);
    
    // text
    var bitmap = document.createElement('canvas');
    var g = bitmap.getContext('2d');
    bitmap.width = 256;
    bitmap.height = 256;
    g.font = '80px Arial';
    g.fillStyle = 'white';
    g.fillText('text', 20, 80);
        
    var geometry = new THREE.PlaneGeometry(180, 180);
    var texture = new THREE.CanvasTexture(bitmap);
    var material = new THREE.MeshStandardMaterial({
        map: texture,
        transparent: true // Comment this and the text appears - but with background
    });
    
    var mesh2 = new THREE.Mesh(geometry, material);    
    cubeGroup.add(mesh2);
    
    // add group to scene
    scene.add(cubeGroup);
  
    window.addEventListener('resize', onWindowResize, false);
}


function onWindowResize() {

    windowHalfX = window.innerWidth / 2;
    windowHalfY = window.innerHeight / 2;

    camera.aspect = window.innerWidth / window.innerHeight;
    camera.updateProjectionMatrix();
  
    renderer.setSize(window.innerWidth, window.innerHeight);
    
}

function animate(now){
    requestAnimationFrame(animate);
  
    cubeGroup.rotation.y += (rotationX - cubeGroup.rotation.y) * 0.05;
    cubeGroup.rotation.x += (rotationY - cubeGroup.rotation.x) * 0.05;
        
    renderer.render(scene, camera);    
}

function findViewCoords(mouseEvent)
{
  var xpos;
  var ypos;
  var w = window.innerWidth;
  var h = window.innerHeight;
  var centerX = w/2;
  var centerY = h/2;

  if (mouseEvent)
  {
    xpos = mouseEvent.pageX - document.body.scrollLeft;
    ypos = mouseEvent.pageY - document.body.scrollTop;
  }
  else
  {
    xpos = window.event.x + 2;
    ypos = window.event.y + 2;
  }
  
  var diffX = xpos - centerX;
  var diffY = ypos - centerY;
  percentX = diffX / centerX;
  percentY = diffY / centerY;
 
  rotationX = percentX/2;
  rotationY = percentY/2; 
}

container.addEventListener("mousemove", findViewCoords);

body {
    margin: 0;
    padding: 0;
    overflow: hidden;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/84/three.js"></script>

<div id="container"></div>

Answer 1

发生这种情况的原因是 Three.js 中的渲染分两个阶段进行。

首先渲染固体的东西..然后是透明的东西。

透明物体按照距相机的距离排序。

因此，通过设置 .transparent = true;您要让文本在第二遍期间渲染，从而渲染在其他几何体之上。

查看不屈不挠的 West Langley 的回答:

Transparent objects in Threejs