getFlatInteriorPoints() {
    if (this.flatInteriorPointsRevision_ != this.getRevision()) {
      const flatCenters = linearRingssCenter(
        this.flatCoordinates,
        0,
        this.endss_,
        this.stride,
      );
      this.flatInteriorPoints_ = getInteriorPointsOfMultiArray(
        this.getOrientedFlatCoordinates(),
        0,
        this.endss_,
        this.stride,
        flatCenters,
      );
      this.flatInteriorPointsRevision_ = this.getRevision();
    }
    return /** @type {Array<number>} */ (this.flatInteriorPoints_);
  }
@return {Array<number>} Flat interior points.