Thanks.
R.E. Boss > -----Oorspronkelijk bericht----- > Van: [email protected] [mailto:programming- > [email protected]] Namens Marshall Lochbaum > Verzonden: vrijdag 8 oktober 2010 22:52 > Aan: 'Programming forum' > Onderwerp: Re: [Jprogramming] Puzzle: line-circle/sphere intersection > > The last line should be R>: ... . Otherwise you just test whether R is > greater than 1. > > Marshall > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of R.E. Boss > Sent: Friday, October 08, 2010 4:39 AM > To: 'Programming forum' > Subject: Re: [Jprogramming] Puzzle: line-circle/sphere intersection > > intrsct=: 4 : 0 > R =. x > 'C S E'=.y > t=. -(S-C) (+/@:* % ] +/@:* ]) E-S > P=. S + t * E - S NB. perihelion > R>= +/&.:*: (-&C) (S,P,:E) {~ (0 < t) + 1 < t > ) > > 2 intrsct 0 0 0;2 1 1;2 2 2 > 1 > > > R.E. Boss > > > -----Oorspronkelijk bericht----- > Van: [email protected] > [mailto:[email protected]] Namens R.E. Boss > Verzonden: donderdag 7 oktober 2010 13:52 > Aan: 'Programming forum' > Onderwerp: Re: [Jprogramming] Puzzle: line-circle/sphere intersection > > That was bad reading from my side. > The formulas should be: > > ((S-C)<R)*.((E-C)<R) -...@+. ((S-C)>R)*.((E-C)>R) > > D=: +&.*:/"1 (S,:E)-"1 C > > (D<R) -...@+.&(*./) D>R > > Apart from that, the mathematics is not correct either. I will give it > another thought. > > > R.E. Boss > > > > -----Oorspronkelijk bericht----- > > Van: [email protected] [mailto:programming- > > [email protected]] Namens Bo Jacoby > > Verzonden: donderdag 7 oktober 2010 13:02 > > Aan: Programming forum > > Onderwerp: Re: [Jprogramming] Puzzle: line-circle/sphere intersection > > > > Hello Boss. > > > > I do not understand your notation. Henry wrote "startpoint S and > > endpoint E". You wrote "endpoints A and B", but you use E in your > pseudo > code. > > Please explain. > > > > It seems to me that you must compute the distances (s) from C to S, > > (e) from C to E and (p) from C to the closest point P, (the > > perihelion), and you must determine (b) if P is between S and E. > > Intersection occurs if (s<R and e>R) or (s>R and e<R) or (b and p<R > and > (s>R or e>R)). > > > > --- Den tors 7/10/10 skrev R.E. Boss <[email protected]>: > > > > Fra: R.E. Boss <[email protected]> > > Emne: Re: [Jprogramming] Puzzle: line-circle/sphere intersection > > Til: "'Programming forum'" <[email protected]> > > Dato: torsdag 7. oktober 2010 09.49 > > > > Since the word 'intersect' is used, I assume you mean the boundary of > > the circle/sphere (and not the area), so that a line segment which is > > completely inside is not intersecting. One point at the boundary > means > > intersecting, I assume. > > So the segment is not intersecting if and only if it is completely > > inside or completely outside the circle/sphere. > > > > > > If the line segment is given by the endpoints A and B, the pseudo > code > > is rather straightforward: > > > > ((A-E)<R)*.((B-E)<R) -...@+. ((A-E)>R)*.((B-E)>R) > > > > so ones gets > > > > D=: +&.*:/"1 (A,:B)-"1 E > > > > (D<R) -...@+.&(*./) D>R > > > > (untested) > > > > > > R.E. Boss > > > > > > > -----Oorspronkelijk bericht----- > > > Van: [email protected] [mailto:programming- > > > [email protected]] Namens Henry Rich > > > Verzonden: woensdag 6 oktober 2010 22:54 > > > Aan: Programming forum > > > Onderwerp: [Jprogramming] Puzzle: line-circle/sphere intersection > > > > > > Given circle/sphere with center C and radius R, and a line-segment > > > with startpoint S and endpoint E, write the J code to tell whether > > > the line-segment intersects the circle/sphere. > > > > > > R is an atom, the rest are lists with 2 or 3 atoms. > > > > > > This problem arises in collision detection for games and > simulators, > > > or if you are trying to see whether a path intersects a round > obstacle. > > > > > > I found a solution whose brevity surprised me. > > > > > > Henry Rich > > > ------------------------------------------------------------------- > - > > > -- For information about J forums see > > > http://www.jsoftware.com/forums.htm > > > > --------------------------------------------------------------------- > - > > For information about J forums see > http://www.jsoftware.com/forums.htm > > > > > > --------------------------------------------------------------------- > - > > For information about J forums see > http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
