@polygonjs/polygonjs/src/core/geometry/builders/indicesFromPoints.ts

node-based WebGL 3D engine https://polygonjs.com

import {BufferGeometry} from 'three';
import {PolyDictionary} from '../../../types/GlobalTypes';

export function indicesFromPoints(new_index_by_old_index: PolyDictionary<number>, old_geometry: BufferGeometry) {
	const index_attrib = old_geometry.index;
	if (index_attrib != null) {
		const old_indices = index_attrib.array;

		const new_indices: number[] = [];

		let old_index: number;
		let new_index: number;
		for (let i = 0; i < old_indices.length; i++) {
			old_index = old_indices[i];
			new_index = new_index_by_old_index[old_index];
			if (new_index != null) {
				new_indices.push(new_index);
			}
		}

		return new_indices;
	}
}