[Scilab-users] A plane intersecting a surface

[Stéphane Mottelet]

Hello Paul,

Le 10/09/2018 à 09:29, Carrico, Paul a écrit :
>
> Dear all
>
> Thanks Christophe, Rafael and Stéphane for the first feedback;
>
> Only obvious things in the code hereafter, but it highlights I guess 
> what I would like to do (to cross section the surface); the results 
> are not really noisy and their number is of about few hundred.
>
> Concerning the Delaunay approach, I thought about it but I've been 
> thinking a simplest solution may exist if I can plot the surface 
> (interpolation from the grid) ?
>
in your set of (x_i,y_i,z_i) 3D points, are the (x_i,y_i) organized on a 
grid, i.e. cartesian product [discrete values of x] times [discrete 
values of y] ?

S.

> Paul
>
> ###########################################
>
> mode(0)
>
> function[*z*]=_saddle_(*x*, *y*)
>
> *z* = *x*^2 - *y*^2
>
> endfunction
>
> function[*z*]=_x_square_(*x*, *d*)
>
> *z* = *x*^2 - *d*^2
>
> endfunction
>
> function[*z*]=_y_square_(*y*, *d*)
>
> *z* = *y*^2 - *d*^2
>
> endfunction
>
> /// surface making ... of course in the real life the surface comes 
> from experimental data (no Cartesian equation is attached on))/
>
> n= 50;
>
> x= linspace(-2,2,n)';
>
> y= linspace(-1,3,n)';
>
> z= feval(x,y,_saddle_);
>
> scf(0);
>
> plot3d(x,y,z);
>
> /// obvious cases/
>
> /// n = (0 1 0) then z = x^2 - d^2/
>
> d= 0;
>
> z1= _x_square_(x,d);
>
> scf(1);
>
> plot(x,z1);
>
> /// n = (1 0 0) then z = d^2 - y^2/
>
> d= 0;
>
> z2= _y_square_(y,d);
>
> scf(2);
>
> plot(x,z2);
>
> -----Message d'origine-----
> De : users [mailto:users-bounces at lists.scilab.org] De la part de Dang 
> Ngoc Chan, Christophe
> Envoyé : lundi 10 septembre 2018 09:15
> À : Users mailing list for Scilab
> Objet : [EXTERNAL] Re: [Scilab-users] A plane intersecting a surface
>
> Hello,
>
> > De : users [mailto:users-bounces at lists.scilab.org] De la part de 
> Rafael Guerra
>
> > Envoyé : samedi 8 septembre 2018 14:52
>
> >
>
> > If your cloud of points behaves well enough, you can interpolate it 
> first into a dense
>
> If nobody is expert in this field, then I could invoke a memory when I 
> was a student.
>
> I've heard about an algorithm using intercept with tetrahedrons,
>
> it was used for surface rendering.
>
> So you might perform a Delaunay tessellation of your cloud,
>
> determine which tetrahedrons are cut
>
> and determine the coordinates of the intercepts.
>
> Or ask some CGI  specialists.
>
> HTH
>
> Regards
>
> --
>
> Christophe Dang Ngoc Chan
>
> Mechanical calculation engineer
>
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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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