[vtkusers] How do I interpolate scalars along the geometric surface?

[Fabio Meneghini]

You're welcome. Please let me (and us all) know when you do it, I
guess it will be very usefull an interpolation method.

Fabio

2009/2/19 Takayoshi Kurachi <kurakurara at gmail.com>:
> Hello Fabio,
>
> Thank you very much for your reply!!
>
> It really helps to understand how to go through the point by point
> operation in VTK. It's very valuable to see the working code! I'll
> do the very similar operation, making it the interpolation across
> the surface.
>
> Thank you!!
> Taka
>
>
>
> Fabio Meneghini wrote:
>>
>> Hi!
>> few weeks ago I faced almost the same kind of problem.
>> The piece of source code I wrote, in C++, act as a moving average
>> filter across the surface. The average is weighted by the distance
>> between the current point and his neighbors. It's quite slow during
>> the execution, since no optimization has been performed (I'm always in
>> short time...).
>> I'm not sure this is what you need, since you have to interpolate
>> scalars across a surface, which is a complete different thing, but I
>> hope this could be of inspiration for you.
>> Good luck!
>>
>> Fabio
>>
>>
>>
>>
>> ---------- Forwarded message ----------
>> From: Fabio Meneghini <fab.meneghini at gmail.com>
>> Date: 2009/1/18
>> Subject: Re: [vtkusers] Fwd: How to smooth (or filter) polydata scalars?
>> To: "Kevin H. Hobbs" <hobbsk at ohiou.edu>, vtkusers at vtk.org
>>
>>
>> To whom it may concern,
>> Thanks to help from Kevin H. Hobbs, I wrote a routine performing
>> PolyData scalar values smoothing.
>>
>> That is, it takes as the actual point value the mean of the neighbor
>> points values (but including also himself) , weighting their values
>> mean by the RATIO of their distance from the actual point AND a
>> maximum tolerance distance.
>> Specifically, It takes into account the current point value, with
>> maximum weighting (that is 1), and the neighbors points values with
>> weighting equal to (1 - d/dmax). This only if d<dmax, otherwise the
>> weighting for that point is null.
>>
>> Please, I would be glad if anyone could give a look at this algorithm:
>> it could be implemented as a method (or even a class). It's working
>> fine for my purposes, but I think it's not very much optimized, since
>> I'm not exactly a hero in programming, yet, so fell free to suggest me
>> how to boost and improve performances...
>> I wrote both the C++ and TCL  versions, of the algorithm, so you don't
>> have excuses! ^__^ Have fun!!!
>>
>> Fabio Meneghini
>>
>>
>> 2009/1/14 Kevin H. Hobbs <hobbsk at ohiou.edu>
>>>
>>> On Wed, 2009-01-14 at 13:38 +0100, Fabio Meneghini wrote:
>>>>
>>>> Thank you very much for your reply. I really appreciated it!
>>>
>>> You're welcome.
>>>
>>>> So, for every vertex of the polydata,
>>>
>>> "Vertex" has a specific meaning in VTK it means a cell with one point.
>>> I'm not much of a jargon nut but this could prevent some confusion as
>>> you search through classes.
>>>
>>>>  I could compute the mean of the scalar values of its neighbors
>>>> (possibly with some weights, depending on their distance from the
>>>> current vertex, and then replace the actual scalar value of current
>>>> vertex with the mean.
>>>
>>> In general yes that's how I'd do it. Do the replacement in a temporary
>>> scalar array or calculate the average from a copy of the scalar array.
>>> That way you won't contaminate the average of the neighbors of later
>>> points with the average of the neighbors of earlier points.
>>>
>>>> waiting for a better suggestion about wich classes do this job
>>>> better,
>>>> Thanks again for the hint...
>>>>
>>> Use of the gradient or gradient magnitude filters might help you with
>>> highpass filters.
>>>
>>>> Fabio
>>>
>>> I'm attaching code that does point (position) smoothing in a particular
>>> way that I need. It should help you walk the polydata.
>