From: Jonathan Gutow <gutow@uw...>  20100608 22:04:00

I'm working on a slicer tool and want to make sure I'm clear about how planes are defined within the transform manager as I want to adjust the slab and depth planes in real time based on user input. Here's my understanding. 1) Planes are defined by point4f's where the x, y, z coordinates define a vector from the origin that is perpendicular to the plane. 2) I assume the plane includes the point at the end of the vector. 3) I'm most confused about the meaning of w (the fourth coordinate) for planes that are not parallel to the screen surface, but fixed in the molecule coordinate system. Can anybody clarify? Thanks, Jonathan Dr. Jonathan H. Gutow Chemistry Department gutow@... UWOshkosh Office: 9204241326 800 Algoma Boulevard FAX:9204242042 Oshkosh, WI 54901 http://www.uwosh.edu/facstaff/gutow 
From: Robert Hanson <hansonr@st...>  20100610 15:32:27
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On Tue, Jun 8, 2010 at 5:03 PM, Jonathan Gutow <gutow@...> wrote: > I'm working on a slicer tool and want to make sure I'm clear about how > planes are defined within the transform manager as I want to adjust the slab > and depth planes in real time based on user input. Here's my understanding. > > 1) Planes are defined by point4f's where the x, y, z coordinates define a > vector from the origin that is perpendicular to the plane. > 2) I assume the plane includes the point at the end of the vector. > 3) I'm most confused about the meaning of w (the fourth coordinate) for > planes that are not parallel to the screen surface, but fixed in the > molecule coordinate system. > > Can anybody clarify? > > plane: ax + by + cz + d = 0 "w" is "d". Then the distance to the origin of the plane is d / sqrt(a^2 + b^2 + c^2) and d is the length of the vector (a, b, c) times the directed distance of the plane to the origin. So in xyzw notation, w is the length of the vector (x,y,z) times the directed distance of the plane to the origin. BOb Thanks, > Jonathan > Dr. Jonathan H. Gutow > Chemistry Department gutow@... > UWOshkosh Office: 9204241326 > 800 Algoma Boulevard FAX:9204242042 > Oshkosh, WI 54901 > http://www.uwosh.edu/facstaff/gutow > > > >  > ThinkGeek and WIRED's GeekDad team up for the Ultimate > GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the > lucky parental unit. See the prize list and enter to win: > http://p.sf.net/sfu/thinkgeekpromo > _______________________________________________ > Jmoldevelopers mailing list > Jmoldevelopers@... > https://lists.sourceforge.net/lists/listinfo/jmoldevelopers >  Robert M. Hanson Professor of Chemistry St. Olaf College 1520 St. Olaf Ave. Northfield, MN 55057 http://www.stolaf.edu/people/hansonr phone: 5077863107 If nature does not answer first what we want, it is better to take what answer we get.  Josiah Willard Gibbs, Lecture XXX, Monday, February 5, 1900 
From: Robert Hanson <hansonr@st...>  20100610 15:32:48
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http://mathworld.wolfram.com/PointPlaneDistance.html On Thu, Jun 10, 2010 at 10:32 AM, Robert Hanson <hansonr@...> wrote: > > > On Tue, Jun 8, 2010 at 5:03 PM, Jonathan Gutow <gutow@...> wrote: > >> I'm working on a slicer tool and want to make sure I'm clear about how >> planes are defined within the transform manager as I want to adjust the slab >> and depth planes in real time based on user input. Here's my understanding. >> >> 1) Planes are defined by point4f's where the x, y, z coordinates define a >> vector from the origin that is perpendicular to the plane. >> 2) I assume the plane includes the point at the end of the vector. >> 3) I'm most confused about the meaning of w (the fourth coordinate) for >> planes that are not parallel to the screen surface, but fixed in the >> molecule coordinate system. >> >> Can anybody clarify? >> >> > plane: ax + by + cz + d = 0 > > "w" is "d". Then the distance to the origin of the plane is > > d / sqrt(a^2 + b^2 + c^2) > > and > > d is the length of the vector (a, b, c) times the directed distance of the > plane to the origin. > > So in xyzw notation, > > w is the length of the vector (x,y,z) times the directed distance of the > plane to the origin. > > BOb > > > Thanks, >> Jonathan >> Dr. Jonathan H. Gutow >> Chemistry Department gutow@... >> UWOshkosh Office: 9204241326 >> 800 Algoma Boulevard FAX:9204242042 >> Oshkosh, WI 54901 >> http://www.uwosh.edu/facstaff/gutow >> >> >> >>  >> ThinkGeek and WIRED's GeekDad team up for the Ultimate >> GeekDad Father's Day Giveaway. ONE MASSIVE PRIZE to the >> lucky parental unit. See the prize list and enter to win: >> http://p.sf.net/sfu/thinkgeekpromo >> _______________________________________________ >> Jmoldevelopers mailing list >> Jmoldevelopers@... >> https://lists.sourceforge.net/lists/listinfo/jmoldevelopers >> > > > >  > Robert M. Hanson > Professor of Chemistry > St. Olaf College > 1520 St. Olaf Ave. > Northfield, MN 55057 > http://www.stolaf.edu/people/hansonr > phone: 5077863107 > > > If nature does not answer first what we want, > it is better to take what answer we get. > >  Josiah Willard Gibbs, Lecture XXX, Monday, February 5, 1900 >  Robert M. Hanson Professor of Chemistry St. Olaf College 1520 St. Olaf Ave. Northfield, MN 55057 http://www.stolaf.edu/people/hansonr phone: 5077863107 If nature does not answer first what we want, it is better to take what answer we get.  Josiah Willard Gibbs, Lecture XXX, Monday, February 5, 1900 