code: public Geometry getPartialEnvelopeGeometry(int indexFrom, int indexTo) {
  		Geometry onePoly = null;
  		Geometry prevPoly = null;
  		if (indexFrom > indexTo || indexFrom < 0 || indexFrom > this.trajectory.getPoseSteering().length-1 || indexTo < 0 || indexTo >= this.trajectory.getPoseSteering().length) throw new Error("Indices incorrect!");
  		for (int i = indexFrom; i <= indexTo; i++) {
  			PoseSteering ps = this.trajectory.getPoseSteering()[i];
  			Geometry rect = makeFootprint(ps);
  			if (onePoly == null) {
  				onePoly = rect;
  				prevPoly = rect;
  			}
  			else {
  				Geometry auxPoly = prevPoly.union(rect);
  				onePoly = onePoly.union(auxPoly.convexHull());
  				prevPoly = rect;
  			}
  		}
  		return onePoly;
  	}
docs: Get a {@link Geometry} representing the spatial envelope between two given indices.
  @param indexFrom The starting index (inclusive).
  @param indexTo The ending index (inclusive).
  @return A {@link Geometry} representing the spatial envelope between two given indices.