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Re: IDLgrPoly[line|gon] and cv_coord [message #33494 is a reply to message #33492]

Wed, 08 January 2003 05:23

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Thomas Gutzler (tgutzler@ee.uwa.edu.au) writes:

> I used to scale every Object to have max 2 Units in each dimension and
> translating it to have 0/0/0 in its center because I discovered that the
> visible area is only [-1..1] in each dimension. I tried to enlarge it
> but without any success. Did I miss something or is that the way to do
> it correctly?

I think you missed something. What you describe is
the default viewplane rectangle. It is certainly
not "wrong" to scale everything to it. It's just
that this particular coordinate system is not
always convenient.

If you are working with images of a particular
size, for example, it is sometimes convenient to
have an "image" coordinate system (0 to 512, say).
I often prefer to have a "normalized" coordinate
system of 0 to 1, since I am more familiar with
how to scale things into this coordinate system
than one that goes from -1 to 1.

The thing about object graphics is, you can do
whatever you like and whatever is convenient for
the problem at hand. But, if you are like me, I
find all of this terribly confusing, and it took
me literally weeks before I could get the components
of a line plot (axes, titles, the line plot itself)
with all the bits showing up in the proper relationship
to one another.

That's why I wrote the NORMALIZE function. That little
guy, which you see in every object graphics program I've
ever written, is magical. It just seems to *know* how
to put things where they need to go. I'm sure I couldn't
write an object graphics program without it, Ronn Kling's
excellent book on the subject not withstanding. :-)

Cheers,

David

--
David W. Fanning, Ph.D.
Fanning Software Consulting, Inc.
Phone: 970-221-0438, E-mail: david@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155

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		Re: IDLgrPoly[line\|gon] and cv_coord By: David Fanning on Wed, 08 January 2003 10:37
		Re: IDLgrPoly[line\|gon] and cv_coord By: Rick Towler on Wed, 08 January 2003 09:55
		Re: IDLgrPoly[line\|gon] and cv_coord By: paul wisehart on Wed, 08 January 2003 05:58
		Re: IDLgrPoly[line\|gon] and cv_coord By: David Fanning on Wed, 08 January 2003 05:23
		Re: IDLgrPoly[line\|gon] and cv_coord By: Thomas Gutzler on Tue, 07 January 2003 23:16
		Re: IDLgrPoly[line\|gon] and cv_coord By: Rick Towler on Tue, 07 January 2003 15:15
		Re: IDLgrPoly[line\|gon] and cv_coord By: David Fanning on Tue, 07 January 2003 14:58
		Re: IDLgrPoly[line\|gon] and cv_coord By: Rick Towler on Wed, 08 January 2003 13:04

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		Re: IDLgrPoly[line\|gon] and cv_coord By: David Fanning on Wed, 08 January 2003 10:37
		Re: IDLgrPoly[line\|gon] and cv_coord By: Rick Towler on Wed, 08 January 2003 09:55
		Re: IDLgrPoly[line\|gon] and cv_coord By: paul wisehart on Wed, 08 January 2003 05:58
		Re: IDLgrPoly[line\|gon] and cv_coord By: David Fanning on Wed, 08 January 2003 05:23
		Re: IDLgrPoly[line\|gon] and cv_coord By: Thomas Gutzler on Tue, 07 January 2003 23:16
		Re: IDLgrPoly[line\|gon] and cv_coord By: Rick Towler on Tue, 07 January 2003 15:15
		Re: IDLgrPoly[line\|gon] and cv_coord By: David Fanning on Tue, 07 January 2003 14:58
		Re: IDLgrPoly[line\|gon] and cv_coord By: Rick Towler on Wed, 08 January 2003 13:04