[英]How to access the BufferGeometry of IFC items in web-ifc-three
我正在尝试获取与我拥有的 expressId 相对应的元素的几何形状,即 BufferGeometry object(不是通过挑选)。
基本上我在问如何遍历 IFC model 并将每个 object 作为单独的 OBJ 导出。
我会注意到我有逆向工程代码来实现 package 的某些版本,但它使用未记录的功能,所以它自然会在以后的版本中中断(代码也是 colors 根据材料的颜色几何所以我不需要一个mtl):
不要复制此代码,它将不起作用
Object.values(bimModel.ifcManager.state.models[bimModel.modelID].items).forEach(type => {
Object.entries(type.geometries).forEach(([id, geometry]) => {
const properties = bimModel.getItemProperties(Number(id))
const numVertices = geometry.getAttribute('position').count
const color = type.material.color.toArray().map(x => x * 255)
const vertexColors = new Uint8Array(Array.from({ length: numVertices }, () => color).flat())
geometry.setAttribute('color', new BufferAttribute(vertexColors, 3, true))
})
})
使它成为 OBJ 而不是 GLTF 的任何具体原因? 我知道您可以将 ifc model 制作成几个 GLTF 文件。
如果您不介意这是 GLTF 结果,我会跟进答案。 谢谢。
这正是我们将模型导出到 glTF 所做的。 基本工作流程是:
让我们看一个从墙上获取所有网格的基本示例。 该过程并不像将每个 IFC 项目作为单独的网格那样简单,但这是使绘制调用最少的代价(否则,浏览器甚至无法支持中等大小的 IFC 文件):
import { IFCWALLSTANDARDCASE } from 'web-ifc';
async function getAllWallMeshes() {
// Get all the IDs of the walls
const wallsIDs = manager.getAllItemsOfType(0, IFCWALL, false);
const meshes = [];
const customID = 'temp-gltf-subset';
for(const wallID of wallsIDs) {
const coordinates = [];
const expressIDs = [];
const newIndices = [];
const alreadySaved = new Map();
// Get the subset for the wall
const subset = viewer.IFC.loader.ifcManager.createSubset({
ids: [wallID],
modelID,
removePrevious: true,
customID
});
// Subsets have their own index, but share the BufferAttributes
// with the original geometry, so we need to rebuild a new
// geometry with this index
const positionAttr = subset.geometry.attributes.position;
const expressIDAttr = subset.geometry.attributes.expressID;
const newGroups = subset.geometry.groups
.filter((group) => group.count !== 0);
const newMaterials = [];
const prevMaterials = subset.material;
let newMaterialIndex = 0;
newGroups.forEach((group) => {
newMaterials.push(prevMaterials[group.materialIndex]);
group.materialIndex = newMaterialIndex++;
});
let newIndex = 0;
for (let i = 0; i < subset.geometry.index.count; i++) {
const index = subset.geometry.index.array[i];
if (!alreadySaved.has(index)) {
coordinates.push(positionAttr.array[3 * index]);
coordinates.push(positionAttr.array[3 * index + 1]);
coordinates.push(positionAttr.array[3 * index + 2]);
expressIDs.push(expressIDAttr.getX(index));
alreadySaved.set(index, newIndex++);
}
const saved = alreadySaved.get(index);
newIndices.push(saved);
}
const geometryToExport = new BufferGeometry();
const newVerticesAttr = new BufferAttribute(Float32Array.from(coordinates), 3);
const newExpressIDAttr = new BufferAttribute(Uint32Array.from(expressIDs), 1);
geometryToExport.setAttribute('position', newVerticesAttr);
geometryToExport.setAttribute('expressID', newExpressIDAttr);
geometryToExport.setIndex(newIndices);
geometryToExport.groups = newGroups;
geometryToExport.computeVertexNormals();
const mesh = new Mesh(geometryToExport, newMaterials);
meshes.push(mesh);
}
viewer.IFC.loader.ifcManager.removeSubset(modelID, undefined, customID);
return meshes;
}
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