问题：
三js-导入时可以检测几何体“孤岛”吗？
华俊弼
我正在将.3DS模型导入Blender 2.72b，然后将它们与三个模型一起导出。js导入/导出插件。这些模型有多个几何“岛”（独立的连接面和顶点组），每个都有自己的材质。我希望能够将每个材质与其对应的孤岛配对，而不必创建单独的三个。几何体对象。经过一番挖掘，我发现了这个问题，建议使用一个3。MeshFaceMaterial可为一个对象实现多个材质。唯一的问题是，该示例中的几何体是一个简单的立方体，而我的模型有数百个面分布在2-5个岛上。
有三个。js是否具有识别网格中几何体“孤岛”的功能？
共有3个答案
连晟
我认为这是正确的方法：
function unmergeGeometryArray(geometry) {
// Asumptions:
// geometry is BufferGeometry
// The geometry has no index duplicates (2 equal positions with different index) neither empty triangles, the geometry has been processed with mergeVertices function
// normal attribute is discarded, can be recomputed after, only color and position attributes are taken into account
const material = new THREE.MeshBasicMaterial({
side: THREE.DoubleSide,
vertexColors: THREE.VertexColors
});
const indexArray = geometry.index.array;
const positionArray = geometry.attributes.position.array;
const positionCount = geometry.attributes.position.count;
const totalTriangles = indexArray.length / 3;
let triangleVisitedArray = new Uint8Array(totalTriangles);
let indexVisitedArray = new Uint8Array(positionCount);
let indexToTriangleIndexMap = [];
let missingVertices = positionCount;
let missingTriangles = totalTriangles;
// Functions:
function computeTrianglesRecursive(index, out){
//console.log("- start of computeTriangles with index:", index);
if (indexVisitedArray[index] === 1 || missingVertices === 0 || missingTriangles === 0) {
return;
}
indexVisitedArray[index] = 1;
missingVertices -= 1;
let triangleIndexArray = indexToTriangleIndexMap[index];
for(let i=0; i<indexToTriangleIndexMap[index].length; i++) {
let triangleIndex = indexToTriangleIndexMap[index][i];
if (triangleVisitedArray[triangleIndex] === 0) {
triangleVisitedArray[triangleIndex] = 1
missingTriangles -= 1;
//console.log("-- index: ", index, "; i: ", i, "; triangleIndex: ", triangleIndex);
out.push(triangleIndex);
childIndex1 = indexArray[triangleIndex*3+1];
computeTriangles(childIndex1, out);
childIndex2 = indexArray[triangleIndex*3+2];
computeTriangles(childIndex2, out);
}
}
}
function computeTriangles(indexTocheck){
let out = [];
let startIndex = indexTocheck;
let indexToCheckArray = [indexTocheck];
let i = 0;
while (i<indexToCheckArray.length) {
let index = indexToCheckArray[i];
if (indexVisitedArray[index] == 0) {
indexVisitedArray[index] = 1;
missingVertices -= 1;
let triangleIndexArray = indexToTriangleIndexMap[index];
for(let j=0; j<indexToTriangleIndexMap[index].length; j++) {
let triangleIndex = indexToTriangleIndexMap[index][j];
if (triangleVisitedArray[triangleIndex] === 0) {
triangleVisitedArray[triangleIndex] = 1;
missingTriangles -= 1;
out.push(triangleIndex);
let rootIndex = indexArray[triangleIndex*3];
let child1Index = indexArray[triangleIndex*3+1];
let child2Index = indexArray[triangleIndex*3+2];
if (indexToCheckArray.indexOf(rootIndex) === -1) {
indexToCheckArray.push(rootIndex);
}
if (indexToCheckArray.indexOf(child1Index) === -1) {
indexToCheckArray.push(child1Index);
}
if (indexToCheckArray.indexOf(child2Index) === -1) {
indexToCheckArray.push(child2Index);
}
}
}
}
i +=1;
}
return out;
}
// In the first loop we reorder indices asc order + generate map
for (triangleIndex=0; triangleIndex<totalTriangles; triangleIndex++) {
const geoIndex1 = indexArray[triangleIndex*3];
const geoIndex2 = indexArray[triangleIndex*3+1];
const geoIndex3 = indexArray[triangleIndex*3+2];
const triangleIndexVertexArray = [ geoIndex1, geoIndex2, geoIndex3 ].sort(function(a, b) {
return a - b;
});
if (indexToTriangleIndexMap[geoIndex1] === undefined) {
indexToTriangleIndexMap[geoIndex1] = [triangleIndex];
} else {
indexToTriangleIndexMap[geoIndex1].push(triangleIndex);
}
if (indexToTriangleIndexMap[geoIndex2] === undefined) {
indexToTriangleIndexMap[geoIndex2] = [triangleIndex];
} else {
indexToTriangleIndexMap[geoIndex2].push(triangleIndex);
}
if (indexToTriangleIndexMap[geoIndex3] === undefined) {
indexToTriangleIndexMap[geoIndex3] = [triangleIndex];
} else {
indexToTriangleIndexMap[geoIndex3].push(triangleIndex);
}
//indexArray[triangleIndex*3] = triangleIndexVertexArray[0];
//indexArray[triangleIndex*3+1] = triangleIndexVertexArray[1];
//indexArray[triangleIndex*3+2] = triangleIndexVertexArray[2];
}
let geometryTriangleArray = [];
let index = 0;
while (index<indexToTriangleIndexMap.length && missingVertices>0 && missingTriangles>0){
let out = [];
if (indexVisitedArray[index] === 0) {
out = computeTriangles(index);
}
if (out.length > 0) {
geometryTriangleArray.push(out);
}
index += 1;
}
let geometryArray = [];
for (let i=0; i<geometryTriangleArray.length; i++) {
let out = {
positionArray: [],
colorArray: [],
indexArray: [],
indexMap: [],
currentIndex: 0
}
let triangleArray = geometryTriangleArray[i];
for (let j=0; j<triangleArray.length; j++) {
let triangleIndex = triangleArray[j];
let rootIndex = indexArray[triangleIndex*3];
if (out.indexMap[rootIndex] === undefined) {
out.indexMap[rootIndex] = out.currentIndex;
// add vertex position and color
out.positionArray.push(
geometry.attributes.position.array[rootIndex*3],
geometry.attributes.position.array[rootIndex*3+1],
geometry.attributes.position.array[rootIndex*3+2]
);
if (geometry.attributes.color != undefined) {
out.colorArray.push(
geometry.attributes.color.array[rootIndex*3],
geometry.attributes.color.array[rootIndex*3+1],
geometry.attributes.color.array[rootIndex*3+2]
);
}
out.currentIndex += 1;
}
let child1Index = indexArray[triangleIndex*3+1];
if (out.indexMap[child1Index] === undefined) {
out.indexMap[child1Index] = out.currentIndex;
// add vertex position and color
out.positionArray.push(
geometry.attributes.position.array[child1Index*3],
geometry.attributes.position.array[child1Index*3+1],
geometry.attributes.position.array[child1Index*3+2]
);
if (geometry.attributes.color != undefined) {
out.colorArray.push(
geometry.attributes.color.array[child1Index*3],
geometry.attributes.color.array[child1Index*3+1],
geometry.attributes.color.array[child1Index*3+2]
);
}
out.currentIndex += 1;
}
let child2Index = indexArray[triangleIndex*3+2];
if (out.indexMap[child2Index] === undefined) {
out.indexMap[child2Index] = out.currentIndex;
// add vertex position and color
out.positionArray.push(
geometry.attributes.position.array[child2Index*3],
geometry.attributes.position.array[child2Index*3+1],
geometry.attributes.position.array[child2Index*3+2]
);
if (geometry.attributes.color != undefined) {
out.colorArray.push(
geometry.attributes.color.array[child2Index*3],
geometry.attributes.color.array[child2Index*3+1],
geometry.attributes.color.array[child2Index*3+2]
);
}
out.currentIndex += 1;
}
// Add indices:
out.indexArray.push(out.indexMap[rootIndex], out.indexMap[child1Index], out.indexMap[child2Index]);
}
const geoPositions = new Float32Array(out.positionArray);
const geoColors = new Float32Array(out.colorArray);
const geoIndices = new Uint32Array(out.indexArray);
const geo = new THREE.BufferGeometry();
geo.name = "G_" + i;
geo.index = new THREE.BufferAttribute(geoIndices, 1, false);
geo.attributes.position = new THREE.BufferAttribute(geoPositions, 3, false);
geo.attributes.color = new THREE.BufferAttribute(geoColors, 3, true);
geo.computeBoundingSphere();
geo.computeBoundingBox();
geometryArray.push(geo);
}
return geometryArray;
}
庄飞
我尝试使用函数，但仍然不精确，它生成的几何图形比未连接的几何图形多：
如果有人能看一下，那就太棒了。
function groupGeometryIntoNonConnectedGeometries(geometry) {
const material = new THREE.MeshBasicMaterial({
side: THREE.DoubleSide,
vertexColors: THREE.VertexColors
});
let geometryArray = [];
const indexArray = geometry.index.array;
const positionArray = geometry.attributes.position.array;
const positionCount = geometry.attributes.position.count;
const color = new THREE.Vector3(geometry.attributes.color.array[0], geometry.attributes.color.array[1], geometry.attributes.color.array[2]);
const totalTriangles = indexArray.length / 3;
let geometryCount = 0;
let indexValueAlreadyVisited = new Uint8Array(indexArray.length);
let structure = [];
/*
* indexValue: {
* child: [ [indexval0, indexval1], [] ],
* parent: null
* }
*/
// Initialize Structure:
for (var vextexIdx=0; vextexIdx<positionCount; vextexIdx++) {
structure[vextexIdx] = {
child: [],
parent: null
}
}
for (idx=0; idx<totalTriangles; idx++) {
const geoIndex1 = indexArray[idx*3];
const geoIndex2 = indexArray[idx*3+1];
const geoIndex3 = indexArray[idx*3+2];
const triangleIndexVertexArray = [ geoIndex1, geoIndex2, geoIndex3 ].sort(function(a, b) {
return a - b;
});
structure[ triangleIndexVertexArray[0] ].child.push(triangleIndexVertexArray[1], triangleIndexVertexArray[2]);
structure[ triangleIndexVertexArray[1] ].parent = triangleIndexVertexArray[0];
structure[ triangleIndexVertexArray[2] ].parent = triangleIndexVertexArray[0];
}
let count = 0;
let currentCount = 0;
let geometryStructureArray = [];
for (let strIdx=0; strIdx<structure.length; strIdx++) {
if (structure[strIdx].parent == null) {
currentCount = count;
geometryStructureArray[currentCount] = {
name: "G_" + currentCount,
indexMap: {},
currentIndex: 0,
indexArray: [],
positionArray: [],
colorArray: []
};
count += 1;
}
if (structure[strIdx].child.length > 0) {
const childLen = structure[strIdx].child.length / 2;
for (let childIdx=0; childIdx<childLen; childIdx++) {
const vertexIndex0 = strIdx;
const vertexIndex1 = structure[strIdx].child[childIdx*2];
const vertexIndex2 = structure[strIdx].child[childIdx*2+1];
const v0 = new THREE.Vector3( positionArray[strIdx*3], positionArray[strIdx*3+1], positionArray[strIdx*3+2] );
const v1 = new THREE.Vector3( positionArray[vertexIndex1*3], positionArray[vertexIndex1*3+1], positionArray[vertexIndex1*3+2] );
const v2 = new THREE.Vector3( positionArray[vertexIndex2*3], positionArray[vertexIndex2*3+1], positionArray[vertexIndex2*3+2] );
// check vertex0
if (geometryStructureArray[currentCount].indexMap[vertexIndex0] == undefined) {
geometryStructureArray[currentCount].indexMap[vertexIndex0] = geometryStructureArray[currentCount].currentIndex;
geometryStructureArray[currentCount].indexArray.push(geometryStructureArray[currentCount].currentIndex);
geometryStructureArray[currentCount].positionArray.push(v0.x, v0.y, v0.z);
geometryStructureArray[currentCount].colorArray.push(color.x, color.y, color.z);
geometryStructureArray[currentCount].currentIndex += 1;
} else {
geometryStructureArray[currentCount].indexArray.push(geometryStructureArray[currentCount].indexMap[vertexIndex0]);
}
// check vertex1
if (geometryStructureArray[currentCount].indexMap[vertexIndex1] == undefined) {
geometryStructureArray[currentCount].indexMap[vertexIndex1] = geometryStructureArray[currentCount].currentIndex;
geometryStructureArray[currentCount].indexArray.push(geometryStructureArray[currentCount].currentIndex);
geometryStructureArray[currentCount].positionArray.push(v1.x, v1.y, v1.z);
geometryStructureArray[currentCount].colorArray.push(color.x, color.y, color.z);
geometryStructureArray[currentCount].currentIndex += 1;
} else {
geometryStructureArray[currentCount].indexArray.push(geometryStructureArray[currentCount].indexMap[vertexIndex1]);
}
// check vertex1
if (geometryStructureArray[currentCount].indexMap[vertexIndex2] == undefined) {
geometryStructureArray[currentCount].indexMap[vertexIndex2] = geometryStructureArray[currentCount].currentIndex;
geometryStructureArray[currentCount].indexArray.push(geometryStructureArray[currentCount].currentIndex);
geometryStructureArray[currentCount].positionArray.push(v2.x, v2.y, v2.z);
geometryStructureArray[currentCount].colorArray.push(color.x, color.y, color.z);
geometryStructureArray[currentCount].currentIndex += 1;
} else {
geometryStructureArray[currentCount].indexArray.push(geometryStructureArray[currentCount].indexMap[vertexIndex2]);
}
}
}
}
// Convert to geometryArray:
const geometryStructureArrayLen = geometryStructureArray.length;
const object3d = new THREE.Object3D();
for (let geoIdx=0; geoIdx<geometryStructureArrayLen; geoIdx++) {
const geo = new THREE.BufferGeometry();
geo.name = "G_" + geoIdx;
const geoPositions = new Float32Array(geometryStructureArray[geoIdx].positionArray);
const geoColors = new Float32Array(geometryStructureArray[geoIdx].colorArray);
const geoIndices = new Uint32Array(geometryStructureArray[geoIdx].indexArray);
//console.log(geoIdx, "geoPositions: ", geoPositions);
//console.log(geoIdx, "geoColors: ", geoColors);
//console.log(geoIdx, "geoIndices: ", geoIndices);
geo.index = new THREE.BufferAttribute(geoIndices, 1, false);
geo.attributes.position = new THREE.BufferAttribute(geoPositions, 3, false);
geo.attributes.color = new THREE.BufferAttribute(geoColors, 3, true);
geo.computeBoundingSphere();
geo.computeBoundingBox();
const mesh = new THREE.Mesh(geo, material);
mesh.name = "M_" + geoIdx;
object3d.add(mesh);
}
//return [structure, geometryStructureArray, object3d, count];
return object3d;
}
顺致敬意，
谷翰飞
不，three.js没有识别网格中几何“岛屿”的功能。
使用MeshFaceMaterial时，WebGLRenderer会将几何体分解为块，每种材质一块。这是因为WebGL支持每个几何体一个着色器。
我不会合并所有几何体，然后使用MeshFaceMaterial，只会让渲染器将单个几何体分开。
如果愿意，可以合并共享单个材质的几何图形。
三js r.69
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