polygonjs-engine/src/core/geometry/operation/Polyhedron.ts

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

import {BufferGeometry} from 'three/src/core/BufferGeometry';
import {Float32BufferAttribute} from 'three/src/core/BufferAttribute';
import {Vector3} from 'three/src/math/Vector3';
// import {Vector2} from 'three/src/math/Vector2';

interface PolyHedronBufferGeometryParameters {
	vertices: number[];
	indices: number[];
	radius: number;
	detail: number;
}

// Angle around the Y axis, counter-clockwise when looking from above.
function azimuth(vector: Vector3) {
	return Math.atan2(vector.z, -vector.x);
}

// Angle above the XZ plane.
function inclination(vector: Vector3) {
	return Math.atan2(-vector.y, Math.sqrt(vector.x * vector.x + vector.z * vector.z));
}

// from three/src/geometries/PolyhedronGeometry
export class PolyhedronBufferGeometry extends BufferGeometry {
	parameters: PolyHedronBufferGeometryParameters;
	constructor(vertices: number[], indices: number[], radius: number, detail: number, points_only: boolean) {
		super();

		this.type = 'PolyhedronBufferGeometry';

		this.parameters = {
			vertices: vertices,
			indices: indices,
			radius: radius,
			detail: detail,
		};

		radius = radius || 1;
		detail = detail || 0;

		// default buffer data

		const vertexBuffer: number[] = [];
		const uvBuffer: number[] = [];
		const vertices_by_pos: Map<number, Map<number, Set<number>>> = new Map();

		// the subdivision creates the vertex buffer data

		subdivide(detail);

		// all vertices should lie on a conceptual sphere with a given radius

		applyRadius(radius);

		// finally, create the uv data

		generateUVs();

		// build non-indexed geometry

		this.setAttribute('position', new Float32BufferAttribute(vertexBuffer, 3));
		this.setAttribute('uv', new Float32BufferAttribute(uvBuffer, 2));

		if (!points_only) {
			this.setAttribute('normal', new Float32BufferAttribute(vertexBuffer.slice(), 3));
			if (detail === 0) {
				this.computeVertexNormals(); // flat normals
			} else {
				this.normalizeNormals(); // smooth normals
			}
		}
		// helper functions

		function subdivide(detail: number) {
			const a = new Vector3();
			const b = new Vector3();
			const c = new Vector3();

			// iterate over all faces and apply a subdivison with the given detail value

			for (let i = 0; i < indices.length; i += 3) {
				// get the vertices of the face

				getVertexByIndex(indices[i + 0], a);
				getVertexByIndex(indices[i + 1], b);
				getVertexByIndex(indices[i + 2], c);

				// perform subdivision

				subdivideFace(a, b, c, detail);
			}
		}

		function subdivideFace(a: Vector3, b: Vector3, c: Vector3, detail: number) {
			const cols = detail + 1;

			// we use this multidimensional array as a data structure for creating the subdivision

			const v: Vector3[][] = [];

			// construct all of the vertices for this subdivision

			for (let i = 0; i <= cols; i++) {
				v[i] = [];

				const aj = a.clone().lerp(c, i / cols);
				const bj = b.clone().lerp(c, i / cols);

				const rows = cols - i;

				for (let j = 0; j <= rows; j++) {
					if (j === 0 && i === cols) {
						v[i][j] = aj;
					} else {
						v[i][j] = aj.clone().lerp(bj, j / rows);
					}
				}
			}

			// construct all of the faces

			for (let i = 0; i < cols; i++) {
				for (let j = 0; j < 2 * (cols - i) - 1; j++) {
					const k = Math.floor(j / 2);

					if (j % 2 === 0) {
						pushVertex(v[i][k + 1]);
						pushVertex(v[i + 1][k]);
						pushVertex(v[i][k]);
					} else {
						pushVertex(v[i][k + 1]);
						pushVertex(v[i + 1][k + 1]);
						pushVertex(v[i + 1][k]);
					}
				}
			}
		}

		function applyRadius(radius: number) {
			const vertex = new Vector3();

			// iterate over the entire buffer and apply the radius to each vertex

			for (let i = 0; i < vertexBuffer.length; i += 3) {
				vertex.x = vertexBuffer[i + 0];
				vertex.y = vertexBuffer[i + 1];
				vertex.z = vertexBuffer[i + 2];

				vertex.normalize().multiplyScalar(radius);

				vertexBuffer[i + 0] = vertex.x;
				vertexBuffer[i + 1] = vertex.y;
				vertexBuffer[i + 2] = vertex.z;
			}
		}

		function generateUVs() {
			const vertex = new Vector3();

			for (let i = 0; i < vertexBuffer.length; i += 3) {
				vertex.x = vertexBuffer[i + 0];
				vertex.y = vertexBuffer[i + 1];
				vertex.z = vertexBuffer[i + 2];

				const u = azimuth(vertex) / 2 / Math.PI + 0.5;
				const v = inclination(vertex) / Math.PI + 0.5;
				uvBuffer.push(u, 1 - v);
			}

			// correctUVs and correctSeam are currently not used
			// as they seem to create incorrect uvs when using points only
			// correctUVs();
			// correctSeam();
		}

		// function correctSeam() {
		// 	// handle case when face straddles the seam, see #3269

		// 	for (let i = 0; i < uvBuffer.length; i += 6) {
		// 		// uv data of a single face

		// 		const x0 = uvBuffer[i + 0];
		// 		const x1 = uvBuffer[i + 2];
		// 		const x2 = uvBuffer[i + 4];

		// 		const max = Math.max(x0, x1, x2);
		// 		const min = Math.min(x0, x1, x2);

		// 		// 0.9 is somewhat arbitrary

		// 		if (max > 0.9 && min < 0.1) {
		// 			if (x0 < 0.2) uvBuffer[i + 0] += 1;
		// 			if (x1 < 0.2) uvBuffer[i + 2] += 1;
		// 			if (x2 < 0.2) uvBuffer[i + 4] += 1;
		// 		}
		// 	}
		// }

		function pushVertex(vertex: Vector3) {
			if (points_only) {
				let mx = vertices_by_pos.get(vertex.x);
				if (mx) {
					const my = mx.get(vertex.y);
					if (my && my.has(vertex.z)) {
						return;
					}
				}
				if (!mx) {
					mx = new Map();
					vertices_by_pos.set(vertex.x, mx);
				}
				let my = mx.get(vertex.y);
				if (!my) {
					my = new Set();
					mx.set(vertex.y, my);
				}
				my.add(vertex.z);
			}
			vertexBuffer.push(vertex.x, vertex.y, vertex.z);
		}

		function getVertexByIndex(index: number, vertex: Vector3) {
			const stride = index * 3;

			vertex.x = vertices[stride + 0];
			vertex.y = vertices[stride + 1];
			vertex.z = vertices[stride + 2];
		}

		// function correctUVs() {
		// 	const a = new Vector3();
		// 	const b = new Vector3();
		// 	const c = new Vector3();

		// 	const centroid = new Vector3();

		// 	const uvA = new Vector2();
		// 	const uvB = new Vector2();
		// 	const uvC = new Vector2();

		// 	for (let i = 0, j = 0; i < vertexBuffer.length; i += 9, j += 6) {
		// 		a.set(vertexBuffer[i + 0], vertexBuffer[i + 1], vertexBuffer[i + 2]);
		// 		b.set(vertexBuffer[i + 3], vertexBuffer[i + 4], vertexBuffer[i + 5]);
		// 		c.set(vertexBuffer[i + 6], vertexBuffer[i + 7], vertexBuffer[i + 8]);

		// 		uvA.set(uvBuffer[j + 0], uvBuffer[j + 1]);
		// 		uvB.set(uvBuffer[j + 2], uvBuffer[j + 3]);
		// 		uvC.set(uvBuffer[j + 4], uvBuffer[j + 5]);

		// 		centroid.copy(a).add(b).add(c).divideScalar(3);

		// 		const azi = azimuth(centroid);

		// 		correctUV(uvA, j + 0, a, azi);
		// 		correctUV(uvB, j + 2, b, azi);
		// 		correctUV(uvC, j + 4, c, azi);
		// 	}
		// }

		// function correctUV(uv: Vector2, stride: number, vector: Vector3, azimuth: number) {
		// 	if (azimuth < 0 && uv.x === 1) {
		// 		uvBuffer[stride] = uv.x - 1;
		// 	}

		// 	if (vector.x === 0 && vector.z === 0) {
		// 		uvBuffer[stride] = azimuth / 2 / Math.PI + 0.5;
		// 	}
		// }
	}
}