Re: Help for a beginner!!

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Gan Wang (rock.csd.sgi.com!sgi.com!uunet.uu.net!ds9!cavalier!gan)
Tue, 8 Apr 1997 19:43:58 -0700

On Apr 8, 10:13am, Andy Shein wrote:
> Subject: Re: Help for a beginner!!
> On Apr 8, 9:27am, Christopher R Volpe wrote:
> > Subject: Re: Help for a beginner!!
> > > The base performer coordinates are y into the screen, x to the right
> > > and z up. This is different from OpenGL
> >
> > Just out of curiosity, why would the Performer designers use a different
> > coordinate system from that used by OpenGL?
>
> I think it was because that is the coordinate system
> used in a lot of graphics books.
> It would have been nice if it was x fwd (into the screen)
> y right and z down. This is the coordinate system used in
> most books I have seen on vehicle dynamics. This way
> positive yaw is to the right like a compass, and
> pitch is positive up.
> BTW how many people would like to see this
> coordinate system supported in the follow on product
> to Perfomer ???
>

In modeling of aircraft/vehicle motion, the coordinates as you mentioned makes
more sense. The convention is positive Gz (z component of G force) points
downward (conveniently to the earth so you don't float to the space under
gravity or high G pulls your blood downward), positive Gx forward and Gy the
side force. Performer must have its reasons for its coordinate system
convention.

Gan

> Andy "too long silent on z-down coordinates" Shein
>
>
> >
> >
> > --
> >
> > Chris Volpe Phone: (518) 387-7766
> > GE Corporate R&D Fax: (518) 387-6560
> > PO Box 8 Email: volpecr++at++crd.ge.com
> > Schenectady, NY 12301 Web: http://www.crd.ge.com/~volpecr
> >-- End of excerpt from Christopher R Volpe
>
>
>
> --
> Andrew Shein SE Stout email: ashein++at++boston.sgi.com
> Silicon Graphics Inc. phone: (508) 562 - 4800
> 1 Cabot Road fax: (508) 562 - 4755
> Hudson, MA 01749 vmail: 59688
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>-- End of excerpt from Andy Shein

-- 


Gan Wang


Cambridge Research Associates            Voice:  703-790-0505 ext.7210
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