| Object graphics questions and comment [message #9709] |
Fri, 08 August 1997 00:00  |
Paul van Delst
Messages: 364
Registered: March 1997
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Senior Member |
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Hello,
I'm in the process of writing a viewer for atmospheric absorption
spectra - the data files of which often contain 1000's of spectra. I
decided to use IDL object graphics for a number of reasons:
- makes it easy to do zoom boxes
- makes it easy to do overplotting on resizeable window (sort of like
David Fannings XWINDOW but without the need for a wrapper)
- makes it easy to add annotation
- in the words of Mr. Fanning, makes me look like an "up-to-date and
with-it IDL programmer".
Anyway, I create a zoom box on a left button down event, add it to my
plot_model and draw the resulting view (info_ptr is a pointer to the
info structure ala D.F. and is stored in the user value of the top level
base) :
(*info_ptr).zbox = obj_new( 'IDLgrPolygon',
$
(*info_ptr).zbox_norm_xcoords, $
(*info_ptr).zbox_norm_ycoords, $
color = [ 0, 255, 0 ], style = 1 )
(*info_ptr).plot_model -> add, (*info_ptr).zbox
(*info_ptr).window -> draw, (*info_ptr).view
For motion events I do the following after updating the dynamic corner
of the zoombox:
old_zbox = (*info_ptr).zbox
(*info_ptr).plot_model -> remove, (*info_ptr).zbox
obj_destroy, old_zbox
(*info_ptr).zbox = obj_new( 'IDLgrPolygon', $
(*info_ptr).zbox_norm_xcoords, $
(*info_ptr).zbox_norm_ycoords, $
color = [ 0, 255, 0 ], style = 1 )
(*info_ptr).plot_model -> add, (*info_ptr).zbox
(*info_ptr).window -> draw, (*info_ptr).view
Now all this works great. I get a lovely zoom box except IT IS SOOOOO
SLOW? I test my code on a 1000 element data set and the zoom box can't
keep up with the mouse motion events. Increase the number of points and
it's unusable.
MY QUESTIONS: Is the snail pace response implicit of IDLs of object
graphics (another e.g. IDLs Insight. Good lord) or is there another way
to do this without having to do a
(*info_ptr).window -> draw, (*info_ptr).view
every time? In Direct Graphics you simply erase ONLY the box and then
redraw ONLY the new box, you don't redraw the entire view. Can this be
done using Object Graphics? The documentation is obtuse and unhelpful.
MY COMMENT: IMO, IDLs Object Graphics is necessary for easier
programming of user friendly data visualisation tools. However, the
speed of Object Graphics verges on being laughable (my perhaps poorly
programmed example above notwithstanding). It is a step backwards and
does not encourage the average IDL programmer (me) to utilise this
powerful tool. My (hopeful) assumption is that future incremental
releases of IDLv5 will contain Object Graphics that produce graphics as
fast or faster than Direct Graphics.
Phew!
I'm curious - who out there are actually using IDLs Object Graphics
capability?
regards,
Paul van Delst
Space Science and Engineering Center
University of Wisconsin-Madison
(608) 265-5357
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| Re: object graphics question [message #37869 is a reply to message #9709] |
Wed, 04 February 2004 06:54  |
btt
Messages: 345
Registered: December 2000
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Senior Member |
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Karsten Rodenacker wrote:
>
> I have a problem with coordinated transformations of IDLgrImage and
> other objects, e.g. IDLgrContour.
>
> Does anybody know why rotating behaves like it does?
> In the small example:
>
> img=read_png( filepath('mineral.png', SUBDIR=['examples','data']))
> m=obj_new('IDLgrModel')
> m->add,obj_new('IDLgrImage',img)
> m->add,obj_new('IDLgrContour',img,color=[255,0,0])
> xobjview,m,/block
>
> rotation shows a quite bizar behaviour.
>
> I would expect that the image moves like one level of the contour object.
>
Hi Karsten,
Yes, that is wierd... but there is a solution.
You should really be rendering a polygon with the image as a texture
map. IDLgrImage are always displayed at Z=0 (or some such place.) To
give the image a real coordinate system you have to attach it to some
spatial object, like a polygon or a surface.
img=read_png( filepath('mineral.png', SUBDIR=['examples','data']))
m=obj_new('IDLgrModel')
oimg = obj_new('IDLgrImage',img)
oimg -> GetProperty, dim = dim
poly = obj_new("IDLgrPolygon", [0,0,dim[0]-1, dim[0]-1], $
[0,dim[1]-1,dim[1]-1, 0], $
color = [255,255,255], $
Texture_Map = oImg,$
Texture_Coord = [[0,0],[0,1], [1,1], [1,0]])
m->add, poly
m->add,obj_new('IDLgrContour',img,color=[255,0,0])
xobjview,m,/block
Cheers,
Ben
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| Re: object graphics question [message #37870 is a reply to message #9709] |
Wed, 04 February 2004 06:08 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Karsten Rodenacker writes:
> I have a problem with coordinated transformations of IDLgrImage and
> other objects, e.g. IDLgrContour.
>
> Does anybody know why rotating behaves like it does?
> In the small example:
>
> img=read_png( filepath('mineral.png', SUBDIR=['examples','data']))
> m=obj_new('IDLgrModel')
> m->add,obj_new('IDLgrImage',img)
> m->add,obj_new('IDLgrContour',img,color=[255,0,0])
> xobjview,m,/block
>
> rotation shows a quite bizar behaviour.
>
> I would expect that the image moves like one level of the contour object.
You will have to put your image on a polygon as
a texture map to get it to rotate. Images
have *never* rotated. I don't know why.
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: Object graphics questions [message #43014 is a reply to message #9709] |
Fri, 11 March 2005 16:54 |
Michael Wallace
Messages: 409
Registered: December 2003
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Senior Member |
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> (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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