src/LaserCutter.ts

import type { Mesh, Scene } from '@babylonjs/core'
import { Animation, Color3, Color4, CubicEase, GlowLayer, Matrix, MeshBuilder, ParticleSystem, StandardMaterial, Texture, TransformNode, Vector3 } from '@babylonjs/core'

export class LaserCutter {
  scene: Scene
  pivot: Mesh
  beam: Mesh
  sparkEmitter: Mesh
  sparks: ParticleSystem

  constructor(scene: Scene) {
    this.scene = scene

    const pivot = this.createLasePivot(scene)
    const sparkEmitter = this.createSparkEmitter(scene)
    const beam = this.createBeam(pivot.position, sparkEmitter.position, scene)
    const sparks = this.createSparks(sparkEmitter, scene)
    const gl = new GlowLayer('GlowLayer', scene)
    gl.addIncludedOnlyMesh(beam)
    gl.intensity = 2

    this.pivot = pivot
    this.sparkEmitter = sparkEmitter
    this.beam = beam
    this.sparks = sparks
  }

  async cut(path: Vector3[]) {
    this.beam.isVisible = true
    this.sparks.start()
    for (let i = 1; i < path.length; i++)
      await this.move(path[i - 1], path[i])
    this.sparks.stop()
    this.beam.isVisible = false
  }

  private async move(from: Vector3, to: Vector3) {
    const { scene } = this
    const SPEED = 1.0
    const frameRate = 1 / (to.subtract(from).length() / SPEED)
    const anim = new Animation('Move', 'position', frameRate, Animation.ANIMATIONTYPE_VECTOR3, Animation.ANIMATIONLOOPMODE_CONSTANT)
    anim.setKeys([
      { frame: 0, value: from },
      { frame: 1, value: to },
    ])
    anim.setEasingFunction(new CubicEase())
    const tn = new TransformNode('Target')
    tn.animations.push(anim)
    const animatable = scene.beginAnimation(tn, 0, 1)
    const trackTarget = () => {
      this.attachTo(tn.position)
    }
    const observer = scene.onBeforeRenderObservable.add(trackTarget)
    await animatable.waitAsync()
    observer?.remove()
  }

  private attachTo(target: Vector3) {
    const start = this.pivot.getAbsolutePosition()
    const direction = target.subtract(start).normalize()
    const offset = direction.negate().scale(0.01)
    this.sparkEmitter.setAbsolutePosition(target.add(offset))

    this.createBeam(this.pivot.getAbsolutePosition(), this.sparkEmitter.getAbsolutePosition(), this.scene, this.beam)
  }

  private createLasePivot(scene: Scene) {
    const laserPivot = MeshBuilder.CreateSphere('Target', { diameter: 0.1 }, scene)
    laserPivot.position = new Vector3(0, 0, 0)
    laserPivot.isVisible = false
    return laserPivot
  }

  private createSparkEmitter(scene: Scene) {
    const sparkEmitter = MeshBuilder.CreateSphere('Spark', { diameter: 0.1, segments: 32 }, scene)
    sparkEmitter.position = new Vector3(0, 0, 0)
    sparkEmitter.isVisible = false
    return sparkEmitter
  }

  private createBeam(start: Vector3, end: Vector3, scene: Scene, mesh?: Mesh) {
    const beam = MeshBuilder.CreateTube('Laser', { path: [start, end], radius: 0.05, instance: mesh }, scene)
    beam.bakeTransformIntoVertices(Matrix.Translation(0, 0, 0))
    const laserBeamMtl = new StandardMaterial('Emissive')
    laserBeamMtl.emissiveColor = new Color3(1, 0, 0)
    beam.material = laserBeamMtl
    return beam
  }

  private createSparks(emitter: Mesh, scene: Scene) {
    const sparks = new ParticleSystem('Sparks', 1000, scene)
    sparks.createPointEmitter(new Vector3(1, 1, 1), Vector3.Up())
    sparks.particleTexture = new Texture('textures/flare.png')
    sparks.emitter = emitter
    sparks.emitRate = 160
    sparks.color1 = new Color4(1, 0.12, 0)
    sparks.color2 = new Color4(1, 0.37, 0)
    sparks.maxSize = 0.15
    sparks.minSize = 0.1
    sparks.minEmitPower = 2
    sparks.maxEmitPower = 6
    sparks.maxLifeTime = 3
    sparks.minLifeTime = 0.5
    sparks.gravity = new Vector3(0, -3, 0)
    return sparks
  }
}