backend/libs/three/geometries/CircleGeometry.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 CircleGeometry extends BufferGeometry {
	constructor(radius = 1, segments = 8, thetaStart = 0, thetaLength = Math.PI * 2) {
		super();

		this.type = 'CircleGeometry';

		this.parameters = {
			radius: radius,
			segments: segments,
			thetaStart: thetaStart,
			thetaLength: thetaLength,
		};

		segments = Math.max(3, segments);

		// buffers

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

		// helper variables

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

		// center point

		vertices.push(0, 0, 0);
		normals.push(0, 0, 1);
		uvs.push(0.5, 0.5);

		for (let s = 0, i = 3; s <= segments; s++, i += 3) {
			const segment = thetaStart + (s / segments) * thetaLength;

			// vertex

			vertex.x = radius * Math.cos(segment);
			vertex.y = radius * Math.sin(segment);

			vertices.push(vertex.x, vertex.y, vertex.z);

			// normal

			normals.push(0, 0, 1);

			// uvs

			uv.x = (vertices[i] / radius + 1) / 2;
			uv.y = (vertices[i + 1] / radius + 1) / 2;

			uvs.push(uv.x, uv.y);
		}

		// indices

		for (let i = 1; i <= segments; i++) {
			indices.push(i, i + 1, 0);
		}

		// 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));
	}

	static fromJSON(data) {
		return new CircleGeometry(data.radius, data.segments, data.thetaStart, data.thetaLength);
	}
}

export { CircleGeometry, CircleGeometry as CircleBufferGeometry };