小编JDS*_*JDS的帖子

有没有办法在现有Mesh的面上更改materialIndex？" 如何更新事物"文档中未对此进行讨论,因此我不确定是否可行.我正在使用WebGLRenderer上下文.

这基本上就是我要做的事情:

// Make a mesh with two materials
var texture = THREE.ImageUtils.loadTexture(IMAGE_URL);
var geometry = new THREE.Geometry();
geometry.materials.push(new THREE.MeshBasicMaterial({ wireframe: true, vertexColors: THREE.FaceColors}));
geometry.materials.push(new THREE.MeshBasicMaterial({ map: texture, overdraw: true}));

whatever.forEach(function(w, i) { 
  geometry.vertices.push(makeVerts(w));

  var materialIndex = 0;
  var color = new THREE.Color(i);
  geometry.faces.push(new THREE.Face4(i*4+0, i*4+1, i*4+2, i*4+3, 
                    null, color, materialIndex));
});

var mesh = new THREE.Mesh(geometry, new THREE.MeshFaceMaterial());
scene.add(mesh)


// Later on, change some faces to a different material

geometry.faces.filter(someFilter).forEach(function(face) {
  face.color = someOtherColor;
  face.materialIndex = 1; …

从可变bytearray类型转换为非可变bytes类型会产生副本吗？是否有与之相关的成本,或者解释器是否将其视为不可变的字节序列,就像在C++中转换char*为a 一样const char* const？

ba = bytearray()
ba.extend("some big long string".encode('utf-8'))

# Is this conversion free or expensive?
write_bytes(bytes(ba))

这是不同的Python 3,bytes它自己的类型和Python 2.7,bytes它只是一个别名str？