[vtkusers] getting pointids from an imagedata

Tue Jul 10 05:37:21 EDT 2001

Hello John,

thanks for answering my questions. I am using a renderwindow. Its actually a
self-written imageviewer by using the Actor2D and setting the origin.

I've the x y coords from the mouse click.

I tried them to convert it with setdisplaypoint, displaytoworld and then get
the worldpoint. Maybe thats the wrong way of conversion?

Could you give me more details / infos on what you mean by computing the
pixel location from origin + offset and scaling?

Well, its very helpful for me to set the scalar so that I can see whether my
point is the correct one...

Matt
----- Original Message -----
From: "John Biddiscombe" <jbiddiscombe at skippingmouse.co.uk>
To: "Matthias Zangl" <zangl at ism-austria.at>; <vtkusers at public.kitware.com>
Sent: Tuesday, July 10, 2001 11:04 AM
Subject: Re: [vtkusers] getting pointids from an imagedata

> Matt
>
> I'm not sure I'm able to help you really. There are so many details of how
> you are displaying your image data (renderwindow or imagewindow -
> drawpixels or imageactor) if you're using an imagewindow then I never
touch
> them so can't help, they may not implement the worldpoint-displaypoint
> features in the same way as the renderwindow. Check also that the slice
> number you're using is being set into your SetDisplayPoint(x,y,lastY)
call.
> I generally do something like this
>
> MouseClick->
>    Get X,Y coords
> Compute pixel location from origin+offsetx/y and scaling
>    pointID follows,
> but as I mentioned in an earlier post last week I think, I don't use an
> imagewindow and have implemented all the image display code myself from
> scratch - this means I know exactly where pixel 0,0 is etc etc and there
> are no problems. I'm afraid you're going to have to use a lot of trial and
> error but if you do have a dataset and want to see if the pixel you've got
> is correct, the easiest way is probably
> imagedata->GetPointData()->GetScalars()->SetScalar(mydubiousPointID,255)
> or something along those lines. Then it should change colour and you can
at
> least test it - n'est pas?
>
> JB
>
> At 14:59 09/07/2001, Matthias Zangl wrote:
> >Hello John,
> >
> >I tried out your suggestion and I am not clear, if everything is working
> >properly:
> >
> >float worldPoint[4];
> >
> >  this->GetRenderer()->SetDisplayPoint(x,y,lastY);
> >  this->GetRenderer()->DisplayToWorld();
> >  this->GetRenderer()->GetWorldPoint(worldPoint);
> >
> >  int pointId =
data->FindPoint(worldPoint[0],worldPoint[1],worldPoint[2]);
> >
> >  float coord[3];
> >  data->GetPoint(pointId,coord);
> >
> >The function FidnPoint seems to return a valid pointId (although the
> >worldPoint-coords are not very familiar for me (0.001....)). But at least
I
> >am getting a pointId. For checking if its valid I tried to get the coords
> >from the point id (with getpoint). But the coords stored in the
coord-array
> >are always 0,5 or -0,5 for all axes.. There should definitly be a way for
> >transforming them to useful coordinates,right?
> >
> >Is there another way for doing something with my point for ensuring that
I
> >got the right one?
> >
> >thx,
> >Matt
> >----- Original Message -----
> >From: "John Biddiscombe" <jbiddiscombe at skippingmouse.co.uk>
> >To: "Matthias Zangl" <zangl at ism-austria.at>;
<vtkusers at public.kitware.com>
> >Sent: Saturday, July 07, 2001 12:25 PM
> >Subject: Re: [vtkusers] getting pointids from an imagedata
> >
> >
> > > Sorry, I misread your request. You'll need to get the window->World
> > > coordinate conversion from
> > > vtkViewPort::DisplayToWorld
> > > and then use findpoint...
> > >
> > >
> > > At 15:29 06/07/2001, John Biddiscombe wrote:
> > > >vtkDataSet::
> > > >int FindPoint (float x, float y, float z)
> > > >int FindPoint (float x[3])
> > > >
> > > >all subclasses (ImageData) implement it and given a 3space
coordinate,
> >you
> > > >can find the point ID of the one you want.
> > > >
> > > >JB
> > > >
> > > >
> > > >At 14:16 05/07/2001, Matthias Zangl wrote:
> > > >>Hello!
> > > >>
> > > >>I am displaying a volume (vtkImageData) - slice by slice on my
screen. I
> > > >>realized it by changing the outputorigin on slicing. Well, that
works
> >well
> > > >>so far. Now I want to get the pointid from a point the user is
selecting
> >on
> > > >>the screen. All I got are the coordinates in the renderwindow. I
suppose
> > > >>I've to take care that they 're calculated dependend on the
resolution
> >and
> > > >>current zoomfactor of my image. Maybe someone have some hints for
me.
> > > >>
> > > >>greatly appreciated,
> > > >>
> > > >>bye,
> > > >>Matt
> > > >>
> > > >>
> > > >>_______________________________________________
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