Create a 3D patch faces matrix from vertices matrix

Hello,

im trying to convert 2D patches to 3D patches (extrude the 2D poligon) . for that purpose i already have a vertices matrix but im trying to build the faces matrix as said in the MATLAB documentation, but i cant follow the logic for 'n' lines polygon, (for example a star shape) . im looking for a function that gets the left matrix and returnes the right matrix. many thanks to the helpers

[KSSV]

Attach/ copy the data .... image snippet will not help us to help you.

[Guy Trakht]

pentagon_3d_vertices = [-0.293 -0.404 0;
                         -0.475 0.154 0;
                                0 0.5 0;
                          0.475 0.154 0;
                         0.293 -0.404 0;
                        -0.293 -0.404 1;
                         -0.475 0.154 1;
                                0 0.5 1;
                          0.475 0.154 1;
                         0.293 -0.404 1]
                     
            %% the first 5 rows are the bottom vertices , the last 5 are the upper 

[KSSV]

Where are the connections?

[Guy Trakht]

sorry for the missing data.. the 6'th point is above the 1'st , 7th' is above 2nd' and so on.. two identicle polygons - one on top the other. i hope this is more clear now

Answer 1

[Guy Trakht]

function [faces_matrix] = vertices2faces (vertices_matrix)
%this function recives vertices matrix for an 'n' lines polygon and
%returnes the faces matrix - only works with extruded straight up polygons 
wall_faces = zeros(length(vertices_matrix)/2,4);
    for i=1:(length(vertices_matrix)/2-1)
        wall_faces(i,:) = [i, i+1, i+1+length(vertices_matrix)/2, i+length(vertices_matrix)/2];
    end
wall_faces (i+1,:) = [length(vertices_matrix)/2, 1, length(vertices_matrix)/2+1, length(vertices_matrix)];
top_and_bottom_faces = [1:length(vertices_matrix)/2;length(vertices_matrix)/2+1:length(vertices_matrix)];

%in a case that the tom and bottom faces are with less vertices then the walls    
    if length(vertices_matrix)/2<4
        faces_matrix =[wall_faces; top_and_bottom_faces, top_and_bottom_faces(:,1)];
    else
        for j=5:length(vertices_matrix)/2
            wall_faces(:,j) = wall_faces(:,1);
        end 
        faces_matrix = [wall_faces; top_and_bottom_faces]; 
    end
end

Answer 2

[KSSV]

Are you looking for something like this?

data = [-0.293 -0.404 0;
                         -0.475 0.154 0;
                                0 0.5 0;
                          0.475 0.154 0;
                         0.293 -0.404 0;
                        -0.293 -0.404 1;
                         -0.475 0.154 1;
                                0 0.5 1;
                          0.475 0.154 1;
                         0.293 -0.404 1]
                     
            %% the first 5 rows are the bottom vertices , the last 5 are the upper 
            
x = data(:,1) ; y = data(:,2) ; z = data(:,3) ; 

yi = linspace(min(y),max(y),10) ; 
zi = linspace(min(z),max(z),10) ; 
[Y,Z] = meshgrid(yi,zi); 
X = griddata(y,z,x,Y,Z) ; 
surf(X,Y,Z)

[Guy Trakht]

no, just want to create the face matrix from the given vertices. without meshing any data.

i appreciate your help