[ncl-talk] What is the spatial interpolation method used by "contouring 1-D data"?

[Mary Haley]

Hi Wenshan,

You're right that the code that does the Delaunay mesh is "triangle.c", and
the code that calls it is in CnTriMeshRenderer.c.  Look for places where
you see:

#ifdef BuildTRIANGLE
. . .
#endif

and this will show you the code that is calling the triangle code.

Note that the triangle.c, triangle.h files are from Jonathan Shewchuk of
Berkeley, and you can find out more about the code at:

http://www.cs.cmu.edu/~quake/triangle.html

--Mary



On Wed, Oct 10, 2018 at 5:04 PM, Wenshan Wang <wenshanw at uci.edu> wrote:

> Hi Dennis,
>
> Thank you for the reply!
> I am so sorry for the delay. I was traveling.
>
> What I tried to understand is the following description of contour1d_1.ncl
> on the webpage 'Contouring one-dimensional X, Y, Z (random) data' (
> https://www.ncl.ucar.edu/Applications/contour1d.shtml):
> "By default, NCL will generate smoothed contours (see first frame) in an
> area enclosed by a convex hull
> <https://en.wikipedia.org/wiki/Convex_hull>of the data".
>
> Based on the links you included and a little digging into the NCL code, is
> it safe to say that:
> 1, the smoothing method is: cubic spline interpolation
> 2, the convex hulls are created using the Delaunay triangulation (the dual
> of Voronoi diagram) by calling 'triangle'?
> But I didn't find the actual calling commands in NCL code.
>
> Best,
> Wenshan
> ------------------------------------------------------------
> ------------------
> Post-doctoral Scholar
> Zender Research Group
> Department of Earth System Science
> University of California, Irvine
> https://sites.google.com/a/uci.edu/wenshanwang/
>
>
> On Sun, Sep 16, 2018 at 3:14 PM Dennis Shea <shea at ucar.edu> wrote:
>
>> Without going into the code, a guess would be:
>> *http://ngwww.ucar.edu/supplements/conpack/#Intro2DSmoothing*
>> <http://ngwww.ucar.edu/supplements/conpack/#Intro2DSmoothing>
>> *http://ngwww.ucar.edu/supplements/dashpack/*
>> <http://ngwww.ucar.edu/supplements/dashpack/>
>> Correct:  it is not "simple 9-point smoothing"
>> ====
>> Not sure what you mean by: "Triangulated irregular networks"
>>
>> * http://www.cs.cmu.edu/~quake/triangle.
>> <http://www.cs.cmu.edu/~quake/triangle.html>html
>> <http://www.cs.cmu.edu/~quake/triangle.html>*
>> <http://www.cs.cmu.edu/~quake/triangle.html>
>>
>>
>>
>> *https://www.ncl.ucar.edu/Document/Graphics/contour_grids.shtml
>> <https://www.ncl.ucar.edu/Document/Graphics/contour_grids.shtml>*
>>
>>
>> <http://www.cs.cmu.edu/~quake/triangle.html>
>>
>>
>> On Wed, Sep 12, 2018 at 4:16 PM, Wenshan Wang <wenshanw at uci.edu> wrote:
>>
>>> Hi NCL-talk,
>>>
>>> What is the spatial interpolation method used in this example
>>> contour1d_1.ncl?
>>> Is it "Triangulated irregular networks"?
>>> Where can I find a more detailed description?
>>>
>>> Also, what is the smoothing method here?
>>> seems not a simple 9-point smoothing.
>>>
>>> Thank you!
>>>
>>> Best,
>>> Wenshan
>>> ------------------------------------------------------------
>>> ------------------
>>> Post-doctoral Scholar
>>> Zender Research Group
>>> Department of Earth System Science
>>> University of California, Irvine
>>> https://sites.google.com/a/uci.edu/wenshanwang/
>>>
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>>
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