[Rd] Re: forwarded message from Ross Ihaka

Kevin Buhr buhr@stat.wisc.edu
29 Jul 2001 21:48:41 -0500

Ross Ihaka wrote to Tom Cook (who CCed it to me):
[ regarding "density" and "angle" for polygon hatching ]
> I have just found a student volunteer to do this.  I will
> know more about how long this will take in about a week.  (Its not a
> huge task, but the student make take while to up to speed on graphics.)


You move fast!  However, I'm in Tom's group and have already done some
work on this.

I have what I believe is a pretty good polygon hatching algorithm
written and running in R.  It's robust when implemented in floating
point arithmetic, runs in time at worst linear in the diameter of the
area and O(n log n) in the number of sides of the polygon, and works
well on my ugly testcases (like 500-point random starbursts,
self-intersecting polygons, and so on).  I don't expect any difficulty
in implementing it as a part of R's "graphics.c".

Unless your student is really, really excited about polygon hatching
(and who wouldn't be!), maybe there's something else you want to force
him or her to volunteer to do.  ;)

With a couple days to clean up the code and write some interface glue,
I should be able to send a pure R implementation to the list for
people to play with and critique, if that sounds okay.


Kevin <buhr@stat.wisc.edu>
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