backend/libs/three/geometries/CylinderGeometry.js

import { BufferGeometry } from '../core/BufferGeometry.js';
import { Float32BufferAttribute } from '../core/BufferAttribute.js';
import { Vector3 } from '../math/Vector3.js';
import { Vector2 } from '../math/Vector2.js';

class CylinderGeometry extends BufferGeometry {
	constructor(
		radiusTop = 1,
		radiusBottom = 1,
		height = 1,
		radialSegments = 8,
		heightSegments = 1,
		openEnded = false,
		thetaStart = 0,
		thetaLength = Math.PI * 2
	) {
		super();
		this.type = 'CylinderGeometry';

		this.parameters = {
			radiusTop: radiusTop,
			radiusBottom: radiusBottom,
			height: height,
			radialSegments: radialSegments,
			heightSegments: heightSegments,
			openEnded: openEnded,
			thetaStart: thetaStart,
			thetaLength: thetaLength,
		};

		const scope = this;

		radialSegments = Math.floor(radialSegments);
		heightSegments = Math.floor(heightSegments);

		// buffers

		const indices = [];
		const vertices = [];
		const normals = [];
		const uvs = [];

		// helper variables

		let index = 0;
		const indexArray = [];
		const halfHeight = height / 2;
		let groupStart = 0;

		// generate geometry

		generateTorso();

		if (openEnded === false) {
			if (radiusTop > 0) generateCap(true);
			if (radiusBottom > 0) generateCap(false);
		}

		// build geometry

		this.setIndex(indices);
		this.setAttribute('position', new Float32BufferAttribute(vertices, 3));
		this.setAttribute('normal', new Float32BufferAttribute(normals, 3));
		this.setAttribute('uv', new Float32BufferAttribute(uvs, 2));

		function generateTorso() {
			const normal = new Vector3();
			const vertex = new Vector3();

			let groupCount = 0;

			// this will be used to calculate the normal
			const slope = (radiusBottom - radiusTop) / height;

			// generate vertices, normals and uvs

			for (let y = 0; y <= heightSegments; y++) {
				const indexRow = [];

				const v = y / heightSegments;

				// calculate the radius of the current row

				const radius = v * (radiusBottom - radiusTop) + radiusTop;

				for (let x = 0; x <= radialSegments; x++) {
					const u = x / radialSegments;

					const theta = u * thetaLength + thetaStart;

					const sinTheta = Math.sin(theta);
					const cosTheta = Math.cos(theta);

					// vertex

					vertex.x = radius * sinTheta;
					vertex.y = -v * height + halfHeight;
					vertex.z = radius * cosTheta;
					vertices.push(vertex.x, vertex.y, vertex.z);

					// normal

					normal.set(sinTheta, slope, cosTheta).normalize();
					normals.push(normal.x, normal.y, normal.z);

					// uv

					uvs.push(u, 1 - v);

					// save index of vertex in respective row

					indexRow.push(index++);
				}

				// now save vertices of the row in our index array

				indexArray.push(indexRow);
			}

			// generate indices

			for (let x = 0; x < radialSegments; x++) {
				for (let y = 0; y < heightSegments; y++) {
					// we use the index array to access the correct indices

					const a = indexArray[y][x];
					const b = indexArray[y + 1][x];
					const c = indexArray[y + 1][x + 1];
					const d = indexArray[y][x + 1];

					// faces

					indices.push(a, b, d);
					indices.push(b, c, d);

					// update group counter

					groupCount += 6;
				}
			}

			// add a group to the geometry. this will ensure multi material support

			scope.addGroup(groupStart, groupCount, 0);

			// calculate new start value for groups

			groupStart += groupCount;
		}

		function generateCap(top) {
			// save the index of the first center vertex
			const centerIndexStart = index;

			const uv = new Vector2();
			const vertex = new Vector3();

			let groupCount = 0;

			const radius = top === true ? radiusTop : radiusBottom;
			const sign = top === true ? 1 : -1;

			// first we generate the center vertex data of the cap.
			// because the geometry needs one set of uvs per face,
			// we must generate a center vertex per face/segment

			for (let x = 1; x <= radialSegments; x++) {
				// vertex

				vertices.push(0, halfHeight * sign, 0);

				// normal

				normals.push(0, sign, 0);

				// uv

				uvs.push(0.5, 0.5);

				// increase index

				index++;
			}

			// save the index of the last center vertex
			const centerIndexEnd = index;

			// now we generate the surrounding vertices, normals and uvs

			for (let x = 0; x <= radialSegments; x++) {
				const u = x / radialSegments;
				const theta = u * thetaLength + thetaStart;

				const cosTheta = Math.cos(theta);
				const sinTheta = Math.sin(theta);

				// vertex

				vertex.x = radius * sinTheta;
				vertex.y = halfHeight * sign;
				vertex.z = radius * cosTheta;
				vertices.push(vertex.x, vertex.y, vertex.z);

				// normal

				normals.push(0, sign, 0);

				// uv

				uv.x = cosTheta * 0.5 + 0.5;
				uv.y = sinTheta * 0.5 * sign + 0.5;
				uvs.push(uv.x, uv.y);

				// increase index

				index++;
			}

			// generate indices

			for (let x = 0; x < radialSegments; x++) {
				const c = centerIndexStart + x;
				const i = centerIndexEnd + x;

				if (top === true) {
					// face top

					indices.push(i, i + 1, c);
				} else {
					// face bottom

					indices.push(i + 1, i, c);
				}

				groupCount += 3;
			}

			// add a group to the geometry. this will ensure multi material support

			scope.addGroup(groupStart, groupCount, top === true ? 1 : 2);

			// calculate new start value for groups

			groupStart += groupCount;
		}
	}

	static fromJSON(data) {
		return new CylinderGeometry(
			data.radiusTop,
			data.radiusBottom,
			data.height,
			data.radialSegments,
			data.heightSegments,
			data.openEnded,
			data.thetaStart,
			data.thetaLength
		);
	}
}

export { CylinderGeometry, CylinderGeometry as CylinderBufferGeometry };