[vtkusers] A Simple Question on vtkContourFilter

[Hayden Smith]

Hi,
    I am not quite clear about binary volume. The original images were gray scale images. But I think definitely some binarization took place when "skinExtractor 0 127.5" is called. If I use "skinExtractor 0 30", the output is quite different. I just want to know how the threshold has been selected. Also I would like to know whether vtkImageCast or vtkImageReader do any filtering of images as I also used these to read and process the images.
   It would be great if I get some clarification.
 
Thanks,
Hayden.
 
  

________________________________
 From: Bill Lorensen <bill.lorensen at gmail.com>
To: Hayden Smith <s_hayden_28 at yahoo.com> 
Cc: VTK Users <vtkusers at vtk.org> 
Sent: Sunday, July 7, 2013 7:04 AM
Subject: Re: [vtkusers] A Simple Question on vtkContourFilter
   


It is not a binary volume, correct?

I would expect that the 127 and 255 isosurfaces would be different.



On Sat, Jul 6, 2013 at 10:03 PM, Hayden Smith <s_hayden_28 at yahoo.com> wrote:

Hi,
>   It is 0 to  255. 
> 
>Thanks,
>Hayden.
>
> 
> From: Bill Lorensen <bill.lorensen at gmail.com>
>To: Hayden Smith <s_hayden_28 at yahoo.com> 
>Cc: "vtkusers at vtk.org" <vtkusers at vtk.org> 
>Sent: Saturday, July 6, 2013 7:05 AM
>
>Subject: Re: [vtkusers] A Simple Question on vtkContourFilter
>   
>
>
>What is the range of your scalar data?
>
>
>
>
>
>On Fri, Jul 5, 2013 at 6:44 PM, Hayden Smith <s_hayden_28 at yahoo.com> wrote:
>
>Hello,
>>      I have attached two images: the first one using "skinExtractor SetValue 0 127.5" and the second one "skinExtractor SetValue 0  255". Both showing the very similar output. My question as binarization on image is performed, how the threshold has been calculated as both values showing the similar output.
>>
>>Thanks,
>>
>>Hayden.
>>
>>
>>
>>
>> 
>> From: Bill Lorensen <bill.lorensen at gmail.com>
>>To: Hayden Smith <s_hayden_28 at yahoo.com> 
>>Cc: "vtkusers at vtk.org" <vtkusers at vtk.org> 
>>Sent: Thursday, July 4, 2013 6:04 AM
>>
>>Subject: Re: [vtkusers] A Simple Question on vtkContourFilter
>> 
>>
>>
>>If your data is 8 bit data, then the effect is similar to thresholding. Set the value to 127.5 and you will see an isosurface that has more character. 
>>
>>
>>
>>On Wed, Jul 3, 2013 at 4:14 PM, Hayden Smith <s_hayden_28 at yahoo.com> wrote:
>>
>>Hello,
>>>     Thanks for the reply. But I need a little  bit clarification. When I use 'skinExtractor SetValue 0 255', it generates one iso-surface. Does it threshold the image into a binary image?
>>>
>>>Thanks again.
>>>
>>>Hayden.
>>>
>>>
>>>
>>>
>>>
>>>
>>> 
>>> From: Bill Lorensen <bill.lorensen at gmail.com>
>>>To: Hayden Smith <s_hayden_28 at yahoo.com> 
>>>Cc: "vtkusers at vtk.org" <vtkusers at vtk.org> 
>>>Sent: Tuesday, July 2, 2013 3:45 PM
>>>Subject: Re: [vtkusers] A Simple Question on vtkContourFilter
>>>  
>>>
>>>
>>>skinExtractor GenerateValues 4 0 255 will extract 4 isosurfaces 
>>>     Value 0: 0
>>>      Value 1: 85
>>>      Value 2: 170
>>>      Value 3: 255
>>>
>>>where
>>>skinExtractor SetValue 0 255
>>>will extract 1 isosurface with value
>>>255
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>On Tue, Jul 2, 2013 at 4:17 PM, Hayden Smith <s_hayden_28 at yahoo.com> wrote:
>>>
>>>Hello,
>>>>         I have a simple question on vtkContourFilter. What is the difference between  the following two pieces of code: 
>>>>
>>>>
>>>>        vtkContourFilter skinExtractor
>>>>                                    skinExtractor SetInput [v16
 GetOutput]
>>>>                                    eval skinExtractor GenerateValues 4 0 255
>>>>                                    skinExtractor Update
>>>>
>>>>
>>>>
>>>>
>>>>       vtkContourFilter skinExtractor
>>>>                                   skinExtractor SetInput [v16 GetOutput]
>>>>                                   skinExtractor SetValue 0 255
>>>>                                   skinExtractor Update 
>>>>
>>>>
>>>>
>>>>
>>>>If I use  'eval skinExtractor GenerateValues 4 0 255' in vtkContourFilter, the reconstructed output is noisy whereas if I use 'skinExtractor SetValue 0 255', the output is better and much clear. Could any one clarify me how these two commands are making the difference in output? 
>>>>
>>>>Thanks in advance.
>>>>
>>>>
>>>>
>>>>Hayden
>>>>
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>>>
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>>>   
>>
>>
>>
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>>   
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