react-native-arkit Cylinder from a to b

ARLineSegment.js

import { ARKit } from 'react-native-arkit'
import React from 'react'

import type { Point3D } from '../../../types'
import { length, center, diff, distance } from '../libs/vectorUtils'

const PI_2 = Math.PI / 2

// thx https://stackoverflow.com/a/37948988/1463534
const eulerAnglesCylinder = (a, b) => {
  const w = diff(a, b)
  const l = length(w)
  let pitchB
  const lxz = Math.sqrt(w.x ** 2 + w.z ** 2)
  if (w.y < 0) {
    pitchB = Math.PI - Math.asin(lxz / l)
  } else {
    pitchB = Math.asin(lxz / l)
  }
  let pitch
  if (w.z === 0) {
    pitch = pitchB
  } else {
    pitch = Math.sign(w.z) * pitchB
  }
  let yaw
  if (w.x === 0 && w.z === 0) {
    yaw = 0
  } else {
    const inner = w.x / (l * Math.sin(pitch))
    if (inner > 1) {
      yaw = PI_2
    } else if (inner < -1) {
      yaw = PI_2
    } else {
      yaw = Math.asin(inner)
    }
  }

  const roll = 0
  return {
    x: pitch || 0,
    y: (yaw || 0) + 0.01, // small offset
    z: roll || 0,
  }
}

export default ({ from, to }) => (
  <ARKit.Cylinder
    position={center(from, to)}
    eulerAngles={eulerAnglesCylinder(from, to)}
    shape={{
      height: distance(from, to),
      radius: 0.01,
    }}
    material={{
      lightingModel: ARKit.LightingModel.Constant,
      color: "red"
    }}
  />
)

vectorUtils.js

// @flow

import type { Point3D } from '../../../types'

export const distance = (a: Point3D, b: Point3D): number =>
  Math.sqrt((b.x - a.x) ** 2 + (b.y - a.y) ** 2 + (b.z - a.z) ** 2)

export const center = (a: Point3D, b: Point3D): Point3D => ({
  x: (b.x + a.x) / 2,
  y: (b.y + a.y) / 2,
  z: (b.z + a.z) / 2,
})

export const diff = (a: Point3D, b: Point3D) => ({
  x: b.x - a.x,
  y: b.y - a.y,
  z: b.z - a.z,
})

export const length = (a: Point3D) => Math.sqrt(a.x ** 2 + a.y ** 2 + a.z ** 2)

/**
 * Returns the angle (rad) of the given line relative to the x axis.
 *
 * @param {Point} start
 * @param {Point} end
 */
export const getLineAngle = (start: Point3D, end: Point3D) => {
  const d = diff(end, start)
  const theta = Math.atan2(d.z, d.x)
  return Math.PI - theta
}