@box2d/lights with box2d-wasm

[scott-cornwell]

If you are trying to use this with box2d/lights and you looked at the Raycasting docs for box2d-wasm you might be trying to do return 0 in your RayHandler ReportFixture(). This will cause lights to sometimes go through walls. You want it to look more like this:

import { RayHandler as Box2DLightsRayHandler } from "@box2d/lights";

class RayHandler extends Box2DLightsRayHandler {
  constructor(box2d, world, gl, fboWidth, fboHeight, viewportWidth, viewportHeight) {
    super(gl, fboWidth, fboHeight, viewportWidth, viewportHeight)
    this.box2d = box2d // the box2d-wasm Box2D instance
    this.world = world // the box2d-wasm b2World instance
  }

  createRayCastCallback(light) {
    let { wrapPointer, b2Fixture, b2Vec2, JSRayCastCallback, destroy, LeakMitigator } = this.box2d
    const { freeLeaked, recordLeak } = new LeakMitigator()
    const baseCallback = new JSRayCastCallback()

    baseCallback.ReportFixture = (fixture_p, point_p, normal_p, fraction) => {
      const fixture = recordLeak(wrapPointer(fixture_p, b2Fixture))
      const point = recordLeak(wrapPointer(point_p, b2Vec2))
      const filterData = recordLeak(fixture.GetFilterData())
      const body = recordLeak(fixture.GetBody())
      light.reportFixture(filterData, body, point, fraction)
      freeLeaked()
      return fraction // very important, do not return 0 or it will go through walls sometimes
    }

    return (point1, point2) => {
     // these HAVE to be b2Vec2 from box2d-wasm, passing the point1, point2 in directly will be ignored
      const start = new b2Vec2(point1.x, point1.y)
      const end = new b2Vec2(point2.x, point2.y)
      this.world.RayCast(baseCallback, start, end)
      destroy(start)
      destroy(end)
    }
  }

  getBodyPosition(body) {
    return body.GetPosition()
  }

  getBodyAngle(body) {
    return body.GetAngle()
  }
}

export { RayHandler }