Move a Point on a 3D surface

Hello,

I have a 3D surface with the information on the vertices and faces in a matrix. I also have a point that is located on the surface. I would like to move this point in x direction on the surface. So that I can be sure that the new point is also on the surface.

Could someone please help me with that problem?

Thank you,

Theresa

Answer 1

[Bruno Luong]

% Generate test mesh
x = 1:15; y = 1:15;
[X,Y] = meshgrid(x,y);
Z = peaks(15);
F = delaunay(X,Y);


% Your points to be projected, with moving xq constant yq
% NOTE: In your case just take the (xknown,yknown) to
% xq = xknown + 2; yq = yknown; to move them at distance 2
xq = linspace(min(x),max(x),101);
yq = 8+zeros(size(xq));

% Build some useful matrices and coordinates in arrays
xyz = [X(:) Y(:) Z(:)]';
xyzF = reshape(xyz(:,F'), 3, 3, []);
baryMat = xyzF;
baryMat(3,:,:) = 1;

figure
trisurf(F,X,Y,Z);
colormap gray
hold on
for k = 1:length(xq)
    xyq = [xq(k); yq(k); 1];
    w = pagemldivide(baryMat, xyq);
    i = find(all(w >= 0, 1), 1); % which face contain the point
    if isempty(i)
        % point outside the mesh
        continue
    end
    xyzq = xyzF(:,:,i) * w(:,:,i);
    plot3(xyzq(1), xyzq(2), xyzq(3), 'g.', 'Markersize', 10)
end

[Theresa Kandels]

Thank you for your help Bruno!

I just have problems to apply the script to my data, as I only have the coordinates of the vertices. Do you know how i can convert the informations of the vertices and the faces to your format?

[Bruno Luong]

But earlier you wrote "I have a 3D surface with the information on the vertices and faces in a matrix."

So what do you have?

In my code Vertice is

 xyz' % n x 3

and face is

F % m x 3

If you only have vertices you might be able to reconstruct connectivity with delaunay as I did.

Explain exactly what you have if you don't want me to guess and fail.

[Theresa Kandels]

Thank you for your answer, this will help!

I'm sorry I'm still very new to this subject.