[vtkusers] Number of points in the surface generated from vtkContourFilter

[Bryn Lloyd]

> 
> Thank you for your detailed information. I just found the points are much
> denser than I expected. My input is an image and the resolution is not high
> actually. By the way, I set the resolution of the image in the unit of
> centimeter. Is the default unit of resolution for the input image the
> millimeter?

I meant pixels/voxels - the units are irrelevant. For instance if you
have an image of 512x512 you will have many more points than if you have
an image of 50x50!



> 
> Thanks,
> -Jinzhong
> 
> 
> -----Original Message-----
> From: Bryn Lloyd [mailto:blloyd at vision.ee.ethz.ch] 
> Sent: Friday, August 07, 2009 12:51 AM
> To: Yang, Jinzhong
> Cc: vtkusers at vtk.org
> Subject: Re: [vtkusers] Number of points in the surface generated from
> vtkContourFilter
> 
> No, the point density of the output of contour filter depends on the 
> density of it's input (image/mesh/what is your input?).
> 
> For images it is running marching cubes (squares), and similar 
> algorithms for other input such as unstructured meshes. The edges of the 
> input grid are checked for a sign change between the two end points. If 
> there is a sign change the edge is bisected and a new point is added. 
> These points define the resulting contour surface.
> 
> You would have reduce the resolution of the input (resample if it is an 
> image), or as you have done use a decimation filter on the output.
> 
> /Bryn
> 
> 
> 
> 
> Yang, Jinzhong wrote:
>> Hi,
>>
>> I just wonder if there is any way to control the number of points in the 
>> surface generated from vtkContourFilter. I use vtkContourFilter to 
>> generate one surface, but the surface has too many points. Currently I 
>> use vtkDecimationPro to reduce the number of points, but this requires 
>> extra time.
>>
>> Thanks a lot if you can help.
>>
>>  
>>
>> -Jinzhong
>>
>>  
>>
>>
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> 


-- 
-------------------------------------------------
Bryn Lloyd
Computer Vision Laboratory
ETH Zürich, Sternwartstrasse 7, ETF C110
CH - 8092 Zürich, Switzerland
Tel: +41 44 63 26668
Fax: +41 44 63 21199
-------------------------------------------------