BUG: Perfomance bug in ClippingPolygonCollection

CesiumJS
1

Hi!

ClippingPolygonCollection.computeIntersectionWithBoundingVolume causes a massive performance hit in the default sandcastle. Something is wrong with the implementation there. Tested on Windows, Nvidia RTX 4090, framerate is about 10fps and a solid +120fps without the clip!

Re-produce:

2

There are some performance issues with clipping polygons. This is already tracked in Improve Clipping Polygon Performance · Issue #12258 · CesiumGS/cesium · GitHub , which contains some additional details about the source. (I don’t see computeIntersectionWithBoundingVolume in the stack trace there, but there are several functions that may be involved here…)

3

Thanks! Thats great info in the ticket about this… I ended up adding a “dirty flag”-style temporary solution:

ClippingPolygon.prototype.computeRectangle = function (result) {
  // TODO: Make it possible to edit the polygons.
  if (!this._computedRectangle) {
    this._computedRectangle = new Rectangle();
    PolygonGeometry.computeRectangleFromPositions(
      this.positions,
      this.ellipsoid,
      undefined,
      this._computedRectangle,
    );
  }
  const res = defined(result) ? result : new Rectangle();
  Rectangle.clone(this._computedRectangle, res);
  return res;
};