[Scilab-users] A plane intersecting a surface

[Carrico, Paul]

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) ?



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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