Metapost intersections (offtopic)

Metapost intersections (offtopic)

[Michal Kvasnicka]

Hallo!

Excuse me plese to ask this offtopic, but I know some of you are quite
experienced
in Metapost.

I do have some general curve. I want to draw just th part of it that
lies inside some
box. This is simple enough if you use the clip command. But such results
I don't like
because ends of the lines are spoiled as cropped.

I thought it would be easy to find the first intersection between the
curve and the box
and draw the part of line (from the beginning to the intersection point)
if the line
is outside the box. Then to cut this part of the path off and repeat the
process. But
the time is changed by subpath command in such a way I don't understand.
Moreover
I don't know what result I can get if the curve would be linear and
would go over
the box.

Has some of you some working code that handles this (or similar)
problem?

Many thanks for any answer and one more excuse for the offtopic.

Your sincerely
Michal Kvasnicka

--
Economics is the only field in which two people can get a Nobel Prize
for saying exactly the opposite things.

Re: Metapost intersections (offtopic)

[Hans Hagen]

At 01:45 PM 5/23/2000 +0200, Michal Kvasnicka wrote:

>process. But
>the time is changed by subpath command in such a way I don't understand.

It is a rather manual job I fear (some color and points added for
educational purposes): 

input mp-tool ;

beginfig(1) ;

path some_line ; some_line := (-100,-100)..(0,50)..(100,100) ;
path some_circ ; some_circ := fullcircle scaled 150 ;
path some_curv ; some_curv := some_circ cutafter point 2  of some_circ ;

pickup pencircle scaled 2 ; draw some_line ; draw some_circ ;

pair point_one ; point_one := some_line intersectionpoint some_circ ;
pair point_two ; point_two := some_line intersectionpoint some_curv ;

pickup pencircle scaled 5 ;
draw point_one withcolor red  ;
draw point_two withcolor blue ;

some_line := some_line cutbefore point_one ;
some_line := some_line cutafter  point_two ;

pickup pencircle scaled 2 ;
drawarrow some_line withcolor green ;
drawarrow reverse some_line withcolor green ;

endfig ;

end .

(It's about time I start writing that book about graphics -) 

Hans

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                                          Hans Hagen | PRAGMA ADE
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Re: Metapost intersections (offtopic)

[Ed L Cashin]

Hans Hagen <pragma@wxs.nl> writes:

> (It's about time I start writing that book about graphics -) 

Sign me up for a copy!

-- 
--Ed Cashin                     PGP public key:
  ecashin@coe.uga.edu           http://www.coe.uga.edu/~ecashin/pgp/