three.js/src/geometries/CircleGeometry.js

import { Geometry } from '../core/Geometry.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';

// CircleGeometry

class CircleGeometry extends Geometry {

	constructor( radius, segments, thetaStart, thetaLength ) {

		super();
		this.type = 'CircleGeometry';

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

		this.fromBufferGeometry( new CircleBufferGeometry( radius, segments, thetaStart, thetaLength ) );
		this.mergeVertices();

	}

}

// CircleBufferGeometry

class CircleBufferGeometry extends BufferGeometry {

	constructor( radius, segments, thetaStart, thetaLength ) {

		super();

		this.type = 'CircleBufferGeometry';

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

		radius = radius || 1;
		segments = segments !== undefined ? Math.max( 3, segments ) : 8;

		thetaStart = thetaStart !== undefined ? thetaStart : 0;
		thetaLength = thetaLength !== undefined ? thetaLength : Math.PI * 2;

		// 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 ) );

	}

}


export { CircleGeometry, CircleBufferGeometry };