[vtkusers] Re: casting one ray

[Nico Vermaas]

Hi John,

That is what I tried also. In fact I take a line from the camera worldcoords to the picked point worldcoords. I do get some good results when I display that probe in a xyplot, I can see the values on the ray then (and I can see that the pick indeed does not stop at the max pixel, but goes right through).

But.. how do I loop over those values? How do I get to that data in the probe?

Nico

====================================================
Nico Vermaas
ASTRON - Westerbork Synthesis Radio Telescope
Schattenberg 1 - 9433 TA Zwiggelte - The Netherlands

tel: +31 593 598710                 
vermaas at astron.nl 
====================================================

>>> "John Biddiscombe" <john.biddiscombe at mirada-solutions.com> 08/27/03 10:53 AM >>>
Just use a probefilter and a linesource with plenty of samples on it, then loop over each probed value to find the max. You can set the line source based on camera view direction and pixel location of screen pixel in world space.

JB


> -----Original Message-----
> From: Nico Vermaas [mailto:vermaas at astron.nl]
> Sent: 27 August 2003 08:37
> To: vtkusers at vtk.org
> Subject: [vtkusers] Re: casting one ray
> 
> 
> Hi,
> 
> But then I am back to square 1 with my original problem for 
> which I am trying to find a solution. 
> Let me explain.
> 
> I am picking on a MIP raycasted volume, but the result is not 
> the maximum pixel along the ray, but a pixel somewhere in the 
> middle of the volume. I don't know where and why the ray 
> stops or why it takes that particular pixel.
> 
> Is there some way to configure the pick? To tell it to go on 
> until it finds some threshhold? Or to return the pixel with 
> the maximum/minimum/average value along the ray?
> 
> Or is there another way to cast one ray and get back the MIP result?
> 
> Nico
> 
> 
> -------------
> Date: Tue, 26 Aug 2003 17:49:22 +0200
> From: "Jean M. Favre" <jfavre at cscs.ch>
> Organization: CSCS
> To: Nico Vermaas <vermaas at astron.nl>
> Cc: vtkusers at public.kitware.com
> Subject: Re: [vtkusers] casting one ray?
> 
> Nico Vermaas wrote:
> > 
> > How can I cast one ray from one screen location?
> > 
> 
> How about the following manual page:
> 
> virtual int vtkPicker::Pick(float selectionX, 
>                             float selectionY, 
>                             float selectionZ, 
>                             vtkRenderer *renderer) 
>        
>       Perform pick operation with selection point provided. 
> Normally the
> first two values for the selection point are x-y pixel coordinate, and
> the third value is =0. Return non-zero if something was successfully
> picked.
>  
> -- 
> Dr. Jean M. Favre,                            email:favre at cscs.ch
> http://www.cscs.ch/people/Favre.html
> CSCS, Swiss Center for Scientific Computing | Tel:  +41 (91) 610.82.40
> Via Cantonale, 6928 Manno, Switzerland      | Fax:  +41 (91) 610.82.82
> 
> --__--__--
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