[vtkusers] vtkThreshold: how to change the parameter to colour instead of remove the areas

[Polly Lina]

Hello Doug,

Thank you so much for your response. 

-----Please refer to the images attached-----

Referring to your suggestion (3), I understand this is the fastest method as
you mentioned. 

I rendered the mean curvature by applying the lut colour. But the areas
shown are not as clean as how I wanted as in extracted by ThresholdByLower.
The areas in Green colour are extracted clearly from vtkThreshold. Actually,
I want to utilize the threshold for this research. 
<http://vtk.1045678.n5.nabble.com/file/t341727/test.jpg> 

My work is to visualize the "hole areas" then calculate the centroids of
them.


I am thinking if there is anyway to change the function of vtkThreshold from
either (a) or (b)

a) NOT to remove the areas but to PAINT the areas with a different colour 

OR 

b) DELETE the areas which meet the criterions but KEEP the areas which DOES
NOT meet the criterions 

It is because the areas that do not meet the criterions are meaningful for
my research.



And also I followed your suggestion (1), I created two mappers and two
actors, (ThresholdByLower=0.085 and ThresholdByUpper=0.085). 

However, the areas extracted by ThresholdByLower are exhibited correctly
(Red colour). But the areas that exhibited by ThresholdByUpper 

(This is the area that I need) are not shown preferably (Blue colour).
Adjacent areas disappeared. So I wonder how this should be connected.

<http://vtk.1045678.n5.nabble.com/file/t341727/above_below.jpg> 
"ThresholdByLower-Criterion is cells whose scalars are less or equal to
lower threshold.

ThresholdByUpper-Criterion is cells whose scalars are greater or equal to
upper threshold."

Thank you again! Happy New Year!

Best wishes,
Polly



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