Re: Clipping og polylines

From: Rene Brun (Rene.Brun@cern.ch)
Date: Wed May 20 1998 - 16:54:37 MEST


Cyril Broude wrote:
> 
> --
> Hi,
> 
> When painting TCutG's in line mode on a TH2 in a pad, everything is fine
> when all
> of the polyline is within the range of the pad or it is completely
> outside of the range. However, if only some of the points are in the
> pad, then TGraph::PaintGraph discards all of the external points and
> happily joins up those which are inside. This would be alright for
> PolyMarkers but not for PolyLines.
> 
> What I would like to do is remove the above feature and add the
> capability for
> user SetClipRectangles to clip on the frame of the histogramme.  Any
> comments?
>

You are right about the expected TGraph behaviour. However, a correct
clipping algorithm should work in the following situations:
  - polyline mode
  - polymarker mode
  - fill area mode
  - smooth mode for the 3 cases above
  - Graph with errors (in x and y)
  - Graph with associated fits.
  - histogram frame or not
  - clip by necessity (log scales)
  - clip on screen & Postscript

The current "naive" algorithm is a minimum implementation
for all cases above. Better algorithms will come with time.

Rene Brun



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