@animech-public/playcanvas/build/playcanvas.dbg/src/scene/geometry/dome-geometry.js

PlayCanvas WebGL game engine

import { SphereGeometry } from './sphere-geometry.js';

/**
 * A procedural dome-shaped geometry.
 *
 * The size and tesselation properties of the dome can be controlled via constructor parameters.
 * Radius is fixed to 0.5.
 *
 * Note that the dome is created with UVs in the range of 0 to 1.
 *
 * @category Graphics
 */
class DomeGeometry extends SphereGeometry {
  /**
   * Create a new CylinderGeometry instance.
   *
   * @param {object} [opts] - An object that specifies optional inputs for the function as follows:
   * @param {number} [opts.latitudeBands] - The number of divisions along the latitudinal axis of the
   * sphere (defaults to 16).
   * @param {number} [opts.longitudeBands] - The number of divisions along the longitudinal axis of
   * the sphere (defaults to 16).
   */
  constructor(opts = {}) {
    var _opts$latitudeBands, _opts$longitudeBands;
    // create a sphere geometry
    const radius = 0.5; // the math and constants are based on a unit sphere
    const latitudeBands = (_opts$latitudeBands = opts.latitudeBands) != null ? _opts$latitudeBands : 16;
    const longitudeBands = (_opts$longitudeBands = opts.longitudeBands) != null ? _opts$longitudeBands : 16;
    super({
      radius,
      latitudeBands,
      longitudeBands
    });

    // post-process the geometry to flatten the bottom hemisphere
    const bottomLimit = 0.1; // flatten bottom y-coordinate
    const curvatureRadius = 0.95; // normalized distance from the center that is completely flat
    const curvatureRadiusSq = curvatureRadius * curvatureRadius; // derived values

    const positions = this.positions;
    for (let i = 0; i < positions.length; i += 3) {
      const x = positions[i] / radius;
      let y = positions[i + 1] / radius;
      const z = positions[i + 2] / radius;

      // flatten the lower hemisphere
      if (y < 0) {
        // scale vertices on the bottom
        y *= 0.3;

        // flatten the center
        if (x * x + z * z < curvatureRadiusSq) {
          y = -bottomLimit;
        }
      }

      // adjust y to have the center at the flat bottom
      y += bottomLimit;
      y *= radius;
      positions[i + 1] = y;
    }
  }
}

export { DomeGeometry };