[Scilab-users] mesh2d - finding identical points
Stéphane Mottelet
stephane.mottelet at utc.fr
Fri Nov 20 13:22:32 CET 2020
Yes, just mesh the set of (u,v) coordinates corresponding to your
(x,y,z) reference points.
S.
Le 20/11/2020 à 13:05, P M a écrit :
> I guess I do have such an u-v-plane.
>
> The background of the background :
>
> The task is to map an image onto a 3D geometry.
>
> The image includes reference points, which correspond to known x-y-z
> coordinates.
>
> So the image plane is (my guess) the u-v-plane.
>
> BR
> Philipp
>
>
>
>
> Am Fr., 20. Nov. 2020 um 12:16 Uhr schrieb Stéphane Mottelet
> <stephane.mottelet at utc.fr <mailto:stephane.mottelet at utc.fr>>:
>
> In order to use mesh2d with your data, there must exist a plane
> (u,v) on which you could project your (x,y,z) data. The mesh
> obtained on projected data (u,v) would give you the triangulation
> of the (x,z,y) data. This won't be possible with mesh2d if you
> take for example scattered points on a sphere. However, any
> non-linear transformation "unfolding" the data could also help to
> use pure 2d tools like mesh2d.
>
> S.
>
> Le 20/11/2020 à 12:05, P M a écrit :
>>
>>
>> Am Fr., 20. Nov. 2020 um 11:47 Uhr schrieb Stéphane Mottelet
>> <stephane.mottelet at utc.fr <mailto:stephane.mottelet at utc.fr>>:
>>
>> Hi again,
>>
>> Le 20/11/2020 à 11:30, P M a écrit :
>>> OK,
>>> some more background:
>>>
>>> I actually want to perform a delaunay triangulation on a set
>>> of X-Y-Z-coordinates.
>> I suppose you mean a triangulation of scattered X-Y-Z but you
>> call mesh2d with X-Y only ?
>>
>>
>> Yes, indeed. And there is the bug in my data.
>> As x-y coordinates repeat, they do have a different z in the
>> original data.
>> But since I call mesh2d with x-y only there are indeed identical
>> points.
>>
>>>
>>> I know of CGLAB, but it seems only available to Scilab
>>> 6.0.x, while I am on Scilab 6.1.0
>> CGLAB is based on a very old version of CGAL and thus is very
>> hard to maintain as is. There is a lot of work...
>>
>>
>> I am currently installing Scilab 6.0 to try CGLAB...
>>
>>>
>>> So the nearest thing to a delaunay triangulation I found is
>>> mesh2d...
>> Yeah. Suboptimal choice indeed...
>>> Because of the delaunay triangulation, I am not sure if the
>>> order of points may change.
>> What do you mean ?
>>
>>
>> The scattered points represent a 3D surface geometry.
>> If the points will be resorted, I could imagine that the
>> triangulation does not fit to the surface geometry anymore.
>>
>>>
>>> About unique:
>>>
>>> The result I get is actual of same size as the input
>>> matrix...I therefore do assume that each point is unique in
>>> the first place (which they actually should).
>>>
>>> What does repeat are individual x, y, z coordinates, but in
>>> different combinations.
>>> So the actual point is different.
>>>
>>>
>>> e.g.: x may repeat, but than the y-z-coordinates are
>>> different from point to point
>>
>> Could you share the data (you can send me a private message) ?
>>
>> S.
>>
>>>
>>> Thanks,
>>> Philipp
>>>
>>>
>>>
>>> Am Fr., 20. Nov. 2020 um 10:57 Uhr schrieb Stéphane Mottelet
>>> <stephane.mottelet at utc.fr <mailto:stephane.mottelet at utc.fr>>:
>>>
>>> Hi Philipp,
>>>
>>> Glad to hear that some people use mesh2d. I know we have
>>> to improve the error message by getting the numbers at
>>> the Fortran level... There is also other errors which
>>> are not easy to fix without knowing the number of the
>>> problematic point (point too close to the boundary, for
>>> example). Can you file a bug on BZ ?
>>>
>>> S.
>>>
>>> Le 20/11/2020 à 10:03, P M a écrit :
>>>> Dear all,
>>>>
>>>> using the mesh2d - function I get an error:
>>>> mesh2di: some points are identical.
>>>>
>>>>
>>>> How to identify these points and remove the duplicates?
>>>>
>>>> There are roughly 500'000 coordinates....
>>>>
>>>> Thank you,
>>>> Philipp
>>>>
>>>> _______________________________________________
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>>>
>>> --
>>> Stéphane Mottelet
>>> Ingénieur de recherche
>>> EA 4297 Transformations Intégrées de la Matière Renouvelable
>>> Département Génie des Procédés Industriels
>>> Sorbonne Universités - Université de Technologie de Compiègne
>>> CS 60319, 60203 Compiègne cedex
>>> Tel : +33(0)344234688
>>> http://www.utc.fr/~mottelet <https://antispam.utc.fr/proxy/2/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/antispam.utc.fr/proxy/2/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/antispam.utc.fr/proxy/1/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/www.utc.fr/~mottelet>
>>>
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>>
>> --
>> Stéphane Mottelet
>> Ingénieur de recherche
>> EA 4297 Transformations Intégrées de la Matière Renouvelable
>> Département Génie des Procédés Industriels
>> Sorbonne Universités - Université de Technologie de Compiègne
>> CS 60319, 60203 Compiègne cedex
>> Tel : +33(0)344234688
>> http://www.utc.fr/~mottelet <https://antispam.utc.fr/proxy/2/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/antispam.utc.fr/proxy/1/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/www.utc.fr/~mottelet>
>>
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>
> --
> Stéphane Mottelet
> Ingénieur de recherche
> EA 4297 Transformations Intégrées de la Matière Renouvelable
> Département Génie des Procédés Industriels
> Sorbonne Universités - Université de Technologie de Compiègne
> CS 60319, 60203 Compiègne cedex
> Tel : +33(0)344234688
> http://www.utc.fr/~mottelet <https://antispam.utc.fr/proxy/1/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/www.utc.fr/~mottelet>
>
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>
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--
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet
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