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Re: Object graphics questions [message #43014 is a reply to message #9709]

Fri, 11 March 2005 16:54

Michael Wallace
Messages: 409
Registered: December 2003

Senior Member

> (3) Is it a hard-and-fast rule that if I am viewing a 240x250 image, I
> just have to set the viewplane rectangle to [0,0,240,250]? I have done
> that but the results don't look right.

No. The VIEWPLANE_RECT is not related to the size of an image. The
coordinates are with respect to normalized space. If you do not do any
normalization, the viewplane will need to be sized according to the data
space (i.e. [xmin, ymin, xmax - xmin, ymax - ymin] for a VIEWPLANE that
fits your plot exactly).

Typically, I will instead calculate the scaling factors for converting
the X and Y data ranges into normalized space. These scaling factors
are set via the [XYZ]COORD_CONV keywords of your graphics objects. The
area of my plot fills the normalized space of [0, 0, 1, 1]. I'll add
some buffer space around this viewplane to allow for annotations and the
like.

I do remember seeing a specific example in the IDL documentation
referring to coordinate transformations with object graphics. Try and
find that section -- it really is buried in there somewhere.

> (4) I have followed David Fanning's advice on how to create symbols,
> but I still don't see any, just a line plot.
> Thanks in advance,

I believe this problem will be resolved when you take care of you
viewplane issues. In your current situation, I sure wouldn't expect to
see normal looking symbols. So, get the VIEWPLANE right and then we'll
revisit this if need be.

-Mike

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[Message index]

		Object graphics questions and comment By: Paul van Delst on Fri, 08 August 1997 00:00
		Re: object graphics question By: btt on Wed, 04 February 2004 06:54
		Re: object graphics question By: David Fanning on Wed, 04 February 2004 06:08
		Re: Object graphics questions By: Michael Wallace on Fri, 11 March 2005 16:54

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