[vtkusers] Visualizing multiple isosurfaces using vtkContourFilter

[Thommen Korah]

Hi Christian,
I noticed your thread where you were trying to do the same. Similar to your example, I ended up calling generateValues to create N contours and mapped it to colors in a lookup table. Thanks for your example.
While this method works correctly for a 125x125x50 volume, a larger 312x312x300 volume of short int causes a segmentation fault in vtkDiscreteMarchingCubesComputeGradient(). The volume has approximately 250 disconnected ROIs labeled from 0-N. Is there a limit on how large the volume can be? Or will the labels cause this error since the class expects the scalars to adhere to a specific layout? 
Thanks,Thommen

Date: Thu, 24 Feb 2011 14:15:35 +0530
Subject: Re: [vtkusers] Visualizing multiple isosurfaces using vtkContourFilter
From: karthik.krishnan at kitware.com
To: thkorah at hotmail.com
CC: vtkusers at vtk.org

 Since this is a labelled image with several label (ids), you could use vtkDiscreteMarchingCubes once on each label of interest instead of vtkContourFilter. This will extract just the interface between the cells containing the label of interest and its neighbors, whatever id they may have.

 
--
karthik


On Thu, Feb 24, 2011 at 4:39 AM, Thommen Korah <thkorah at hotmail.com> wrote:


Thanks for your help. I decided to use the first method with separate filters. I have multiple segmented regions, and each voxel stores the id that it belongs to. So all cells belonging to object 3 will store the number 3. 


But when I create cf3 filter and call cf3->setValue(0,3), it creates the isosurface using all cells. My intent is to create the surface only using cells storing 3. Any idea why this might be?


Thanks.

> Date: Wed, 23 Feb 2011 08:23:29 -0500
> Subject: Re: [vtkusers] Visualizing multiple isosurfaces using vtkContourFilter
> From: bill.lorensen at gmail.com

> To: thkorah at hotmail.com
> CC: vtkusers at vtk.org 



> 
> There are two ways to do this:
> 
> 1) Create two ContourFilters. Use cf1->SetValue(0,val1) and
> cf2->SetValue(0,val2).
> You will need 2 mappers and actors.

> 2) Create one ContourFilter. Use cf->SetValue(0,val1) and cf->SetValue(1,val2).
> You will need 1 mapper and actor.
> 
> Both use share the same memory.
> 
> Coloring is easier in case 1).

> mapper1->SetInput(cf1->GetOutput());
> mapper1->ScalarVisibilityOff();
> actor1->SetMapper(mapper1);
> actor1->GetProperty()->SetDiffuseColor(r,g,b);
> mapper2->SetInput(cf2->GetOutput());

> mapper2->ScalarVisibilityOff();
> actor2->SetMapper(mapper2);
> actor2->GetProperty()->SetDiffuseColor(r,g,b);
> 
> Case 2 is trickier and involves mucking with lookup tables.
> 

> 
> 
> On Wed, Feb 23, 2011 at 1:16 AM, Thommen Korah <thkorah at hotmail.com> wrote:
> > Hi,
> > I have a pointcloud on which I perform segmentation to extract different

> > structures projecting out of a flat surface (a table for example). The
> > pointcloud is stored in a voxel data structure. I would now like to
> > visualize these segmented regions by creating  isosurfaces using

> > vtkContourFilter for each object. How can I generate multiple surfaces (eg.
> > book and a cup lying on the table) using the same shared data in memory? I
> > would also like to visualize each segmented region in a different color.

> > Thanks.
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