| Re: Mysterious disappearing objects (bugs in IDLgrWindow::Draw) [message #26419 is a reply to message #26412] |
Wed, 29 August 2001 08:05   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Martin Lowry (m.lowry@hull.ac.uk) writes:
> I'm new to this group but have been watching for a couple of weeks and
> seen the expertise that is present here DF, CM ... So maybe somebody
> cam help me out.
> I've constructed an object that displays medical images acquired in
> 4D, ie x, y, z & time (typical dimensions 256 x 256 x 10 x 35). Onto
> the display I can draw ROIs and attach them to the models. Now come
> the tricky bit, the regions can be viewed on all slices in the volume
> OR only on that slice on which they were drawn (slice number stored in
> UVALUE of IDLgrROI). I call this 2D & 3D mode respectively and provide
> a button to toggle between them. Sometimes when I do this some of the
> ROIs don't get redrawn! When I interogate the graphics model hierachy
> (?sp.) they are clearly in the right place but dont appear on the
> screen! Are there either bugs in IDLgrWindow::Draw or am I missing
> something in the transfer?
> The following diagram might help:
> oView
> |
> --------------------------------------------------
> | | |
> TextModel 2D_ROI_Model [array of ImageModels]
> | | |
> ------------ ---------- 3D_ROI_Models
> | | | | | | |
> Txt Txt Txt ROI ROI ROI -----------
> | | |
> ROI ROI ROI
>
> Only 1 imagemodel is connected to the view at any one time and this
> carries with it its own 3D_ROI_Model and ROIs. The trick in the 2D/3D
> switch is to remove ROIs from 3D_ROI_Model and add them to
> 2D_ROI_Model, or vice-versa.
> Q: Why do some of the ROIs disappear?
It is really hard to say why things disappear in object
graphics. Perhaps you are using the wrong magical incantations. :-)
But I suspect the problem may relate to rendering order,
especially if you are moving things around in the graphics
hierarchy. I suggest you put the ROI objects at a slightly
positive Z value. This will put them in front of the image,
which I presume is a Z=0. Then they should show up clearly
all the time.
Best Regards,
David
P.S. Let's just say the proper incantations can
sometimes be found in Tolkin's wonderful trilogy.
--
David W. Fanning, Ph.D.
Fanning Software Consulting
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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