Defining Triangular mesh with delaunay and inpolygon ?

Hello everyone;

I want to draw my shape functions in 3D over triangular domain:

S1=-1+2x+2y, shape functions contains x and y values.

I can triangulize the mesh (obtain 2 triangle)

[x,y] = meshgrid(0:1,0:1);

tri = delaunay(x,y);

trisurf(tri,x,y,zeros(size(x)))

But I want to only use points from one triangle.

I tried to use inpolygon but I dont understand how it works ?

Answer 1

[John D'Errico]

Easy peasy. And there is no need to bother with inpolygon here.

[x,y] = meshgrid(0:.1:1);
xy = [x(:),y(:)];
xy(xy(:,1) > xy(:,2),:) = [];
tri = delaunayn(xy);
zfun = @(x,y) 1 + 2*x + 2*y;
z = zfun(xy(:,1),xy(:,2));
H = trisurf(tri,xy(:,1),xy(:,2),z);
H.EdgeColor = 'none';
H.FaceColor = 'interp';
xlabel X
ylabel Y
grid on
box on

Note that my use of a finer mesh allows you to have had a more complicated surface, with some curvature in there, even though the function you indicated was purely planar.

As necessary IF that shape function is nonlinear, make sure you know how to use the .* and .^ and ./ operators to allow for vectorized evaluation in the function.

[eda yilmas]

Thank you so much :)

I try to understand what u did in your code step by step, I only change the following step

xy(xy(:,1) > xy(:,2),:) = [];

to define another triangular mesh :)

Have a good day