三.js渲染普通几何体的白色部分

Three.js render white part of plain geometry

本文关键字：几何体 白色部 js      更新时间：2023-09-26

我正在尝试将这个plainGeometry变成这个（一种掩码）。

这段代码有效：（总而言之，创建两种材料，将平面划分为段，并用MeshFaceMaterial决定每种材料是哪种材料） 

   Button.onClick(function () {
            var obj = editor.selected;
            var material = obj.material;
            var tex = material.map;
            var objHeight = obj.geometry.parameters.height;
            var objWidth = obj.geometry.parameters.width;
            var texHeight = tex.image.height;
            var texWidth = tex.image.width;
            var geometry = new THREE.PlaneGeometry(objWidth, objHeight, objWidth, objHeight);
            var facesNum = objHeight * objWidth * 2;
            var facesX = objWidth * 2;
            var facesInX = texWidth * 2;
            var materials = [];
            materials.push(material);
            materials.push(new THREE.MeshBasicMaterial({ }));
            for (var i = 0; i < facesNum; i++) {
                if ((i % facesX >= objWidth - texWidth) &&
                    (i % facesX <= (facesInX + objWidth - texWidth - 1)) &&
                    (i <= (texHeight * objWidth * 2) - 1)) {
                    geometry.faces[i].materialIndex = 0;
                }
                else {
                    geometry.faces[i].materialIndex = 1;
                }
            }
            obj.geometry = geometry;
            obj.material = new THREE.MeshFaceMaterial(materials);
            editor.signals.materialChanged.dispatch(obj);

        });

但我想知道是否有更简单的方法。有什么建议吗？

另一种方法是在纹理上使用 Alpha 通道。 您可以使用 Gimp 或 Photoshop 执行此操作。

然后复制网格，并在材质上使用多边形偏移因子将其推出轴。 将背景材质应用于第一个网格，将具有 alpha 纹理的前景材质应用于第二个网格。看到这个小提琴阿尔法测试。（您可能需要禁用跨域访问安全性，以便纹理可以在此小提琴中加载，如果您使用 --disable-web-security 标志运行它，Chrome 将允许这样做）此方法的优点是图像可以是任何形状和位置，并且不需要适合几何面。

如果您使用的几何图形很复杂，另一种方法是使用 Three.DecalGeometry 切割出网格块，并在材质上用多边形偏移因子将其移动一点。为此，请参阅三.js贴花示例。

示例小提琴的来源如下：

var renderer;
var pointLight;
var scene;
var plane1;
var plane2;
function addPlane()
{
   var material1 = new THREE.MeshPhongMaterial({ color: 0xFFFFFF });
   var material2;
   var loader = new THREE.TextureLoader();
   loader.load('http://i.imgur.com/ETdl4De.png',
     function ( texture ) {     
          var material2 = new THREE.MeshPhongMaterial({
      color: 0xFFFFFF,
      map: texture,
      alphaTest: 0.7,
      polygonOffset: true,
            polygonOffsetFactor: - 4,
     });
   var geometry1 = new THREE.PlaneGeometry(12, 12, 12, 12);
   var geometry2 = geometry1.clone();   
   plane1 = new THREE.Mesh(geometry1,material1);      
   plane2 = new THREE.Mesh(geometry2,material2);      
   scene.add(plane2);
   scene.add(plane1);
    }
);
}
(function() {
    'use strict';
    scene = new THREE.Scene();
    var camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.01, 10000);
    renderer = new THREE.WebGLRenderer();
    renderer.setSize(window.innerWidth, window.innerHeight);                 
    document.body.appendChild(renderer.domElement);
        addPlane();
    camera.position.z = 52;
    pointLight = new THREE.DirectionalLight(0xffffff,1);
    pointLight.position.x = 11;
    pointLight.position.y = 5;
    pointLight.position.z = 25;
    scene.add(pointLight);
    var reqAnimFrame = window.requestAnimationFrame ||          window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.msRequestAnimationFrame;
    var render = function() {
        reqAnimFrame(render);        
        renderer.render(scene, camera);
    };
    render();
}());

最终做到了： 

var obj = editor.selected;
var tex = obj.material.map.;
var materials = [];
materials.push(new THREE.MeshBasicMaterial({ map: tex }));
materials.push(new THREE.MeshBasicMaterial({}));
var material = new THREE.MeshFaceMaterial(materials);
var objHeight = obj.geometry.parameters.height;
var objWidth = obj.geometry.parameters.width;
var texHeight = tex.image.height;
var texWidth = tex.image.width;
tex.repeat = new THREE.Vector2(3, 3);
tex.offset = new THREE.Vector2(0, 0);
var geometry = new THREE.PlaneGeometry(objWidth, objHeight, 3, 3);
var v = geometry.vertices;
var facesNum = geometry.faces.length;
v[1] = new THREE.Vector3(-texWidth / 2, objHeight / 2, 0);
v[2] = new THREE.Vector3(texWidth / 2, objHeight / 2, 0);
v[5] = new THREE.Vector3(-texWidth / 2, (objHeight / 2) - texHeight, 0);
v[6] = new THREE.Vector3(texWidth / 2, (objHeight / 2) - texHeight, 0);
v[9] = v[13];
v[10] = v[14];
v[4] = v[8] = v[12];
v[7] = v[11] = v[15];
for (var i = 0; i < facesNum; i++) {
    if (i !== 2 && i !== 3) geometry.faces[i].materialIndex = 1;
}
obj.material = material;
obj.geometry = geometry;
editor.signals.materialChanged.dispatch(obj);
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