polygonjs-engine/dist/src/core/geometry/util/Circle.js

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

import {CoreMath} from "../../math/_Module";
import {Vector2 as Vector22} from "three/src/math/Vector2";
import {Float32BufferAttribute} from "three/src/core/BufferAttribute";
import {BufferGeometry as BufferGeometry2} from "three/src/core/BufferGeometry";
export class CoreGeometryUtilCircle {
  static positions(radius, segments_count, arc_angle = 360) {
    const radian_per_segment = CoreMath.degrees_to_radians(arc_angle) / segments_count;
    const positions = [];
    for (let i = 0; i < segments_count; i++) {
      const point_radian = radian_per_segment * i;
      const x = radius * Math.cos(point_radian);
      const y = radius * Math.sin(point_radian);
      positions.push(new Vector22(x, y));
    }
    return positions;
  }
  static create(radius, segments_count, arc_angle = 360) {
    const positions_2d = this.positions(radius, segments_count, arc_angle);
    const positions = [];
    const indices = [];
    let position_2d;
    for (let i = 0; i < positions_2d.length; i++) {
      position_2d = positions_2d[i];
      positions.push(position_2d.x);
      positions.push(position_2d.y);
      positions.push(0);
      if (i > 0) {
        indices.push(i - 1);
        indices.push(i);
      }
    }
    indices.push(segments_count - 1);
    indices.push(0);
    const geometry = new BufferGeometry2();
    geometry.setAttribute("position", new Float32BufferAttribute(positions, 3));
    geometry.setIndex(indices);
    return geometry;
  }
}