sphere.js

export function sphere (radius, meridians, parallels) {
  const vertices = []
  for (let i = 0; i < parallels; ++i) {
    const polar = Math.PI * i / (parallels - 1)
    for (let j = 0; j < meridians; ++j) {
      const azimuth = 2.0 * Math.PI * j / meridians
      vertices.push(sphericalToCartesian(radius, azimuth, polar))
    }
  }

  const indices = []

  for (let i = 0; i < parallels - 1; ++i) {
    const currentRowStart = meridians * i
    const nextRowStart = (meridians * (i + 1))

    for (let j = 0; j < meridians; ++j) {
      indices.push(
        currentRowStart + j,
        nextRowStart + j,
        nextRowStart + (j + 1) % meridians,

        currentRowStart + j,
        nextRowStart + (j + 1) % meridians,
        currentRowStart + (j + 1) % meridians
      )
    }
  }

  return {
    vertices,
    indices
  }
}

function sphericalToCartesian (radius, azimuth, polar) {
  return [
    radius * Math.sin(polar) * Math.cos(azimuth),
    radius * Math.cos(polar),
    radius * Math.sin(polar) * Math.sin(azimuth)
  ]
}