Subject:
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Re: Rotating a part?
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Newsgroups:
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lugnet.cad
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Date:
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Thu, 21 Jan 1999 21:35:04 GMT
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Viewed:
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726 times
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Ah. You can't apply the solution given, because you need to find the
axis of rotation. That axis is the vector which is normal to the
vertical line through the current insertion point and the ending
insertion point. There's probably also information about finding that
vector in the c.g.a FAQ.
Steve
> > At this point, it's more a math question than a computer graphics question.<<
Generally, computer graphics questions *are* math questions.
Steve
On Thu, 21 Jan 1999 20:28:28 GMT, "John VanZwieten"
<john_vanzwieten@msn.com> wrote:
> This seems designed to rotate points given an angle and a rotation axis.
> I'm trying to determine what angle(s) to use given a line between two
> points. Also, I'm not a programmer, so I'm basically stuck with formulas I
> can use in a spreadsheet.
>
> Perhaps being more specific will help. Each segment of the flexible hose is
> a cylinder with a hemisphere sticking out the bottom end. The insertion
> point is at the "apex" of the hemisphere. The cylinder is oriented around
> the y axis. To look right, each segment should be oriented around a line
> from its own insertion point to the insertion point of the next segment.
>
> Using a beizier spline formula, I have calculated the insertion points of
> all 50 segments of the hose. I have also used Linc's spreadsheet (and your
> e-mail on the subject) to enable me to transform the part given angles of
> rotation about x,y, and z axes. The "missing link" is that my initial
> attempt to calculate how many degrees to rotate each segment (and on what
> axes) was incorrect. At this point, it's more a math question than a
> computer graphics question. Or, maybe I'm going about this the wrong way
> and there is a way to transform the part directly based on it's insertion
> point and the next insertion point.
>
> -John Van
>
>
> Steve Bliss wrote in message <36a76ead.7975214@lugnet.com>...
> > On Thu, 21 Jan 1999 15:00:57 GMT, "John VanZwieten"
> > <john_vanzwieten@msn.com> wrote:
> >
> > > L-cad is down, and I really would like help with this:
> > >
> > > I have point A (x,y,z) and point B (x',y',z'). I want to rotate a part
> > > (with its insertion point at A) so that it is perpendicular to the line • AB.
> > > How do I calculate the angles of rotation about each axis? Do I need to
> > > rotate on three axes, or is two sufficient?
> >
> > Here's a better answer than the one I sent to L-CAD (which I assume is
> > still in listserv limbo). This is a quote from the
> > comp.graphics.algorithms FAQ. But first, info on where to get the
> > complete FAQ:
>
>
>
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Message is in Reply To:
 | | Re: Rotating a part?
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| This seems designed to rotate points given an angle and a rotation axis. I'm trying to determine what angle(s) to use given a line between two points. Also, I'm not a programmer, so I'm basically stuck with formulas I can use in a spreadsheet. (...) (25 years ago, 21-Jan-99, to lugnet.cad)
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