MATLAB: Colouring Tetramesh – Element wise

delauneyfinite elementsMATLABtetrahedratetramesh

I'm working with tetrahedral finite elements. I can happily set up a mesh and work with said mesh. A really simple example code then gives the following with 72 elements:
clear,close all; clc; dbstop if error;
Nx = 4; Ny =3; Nz = 3; %No. Nodes Nx*Ny Ny = odd
%Variables to create Mesh:

a = 1; b = 1; c = 2;
X = linspace(0,a,Nx); Y = linspace(0,c,Ny); Z = linspace(0,a,Nz);
[X,Y,Z] = meshgrid(X,Y,Z); X = X(:); Y = Y(:); Z=Z(:);
%Meshing:
TRI = delaunay(X,Y,Z);
N = [X,Y,Z];              %Node Coordinates Vector
%figure; triplot(TRI,X,Y);
figure; tetramesh(TRI,[X(:),Y(:),Z(:)]), xlabel('x'),ylabel('y'),zlabel('z');
As a part of my model, each individual element is assumed to be homogoenous and as such has a material property associated with it which for the example here is given by:
NE = size(TRI,1); %Number of Elements
Elements = 1:NE;
Rho_e = zeros(NE,1);
Rho_e(Elements(sum(Y(TRI) <= b,2)==3)) = rho;
When I'm working with triangles in 2D. I can make use of trisurf and create a plot of the material properties:
Nx = 13; Ny =13; %No. Nodes
%Variables to create Mesh:
a = 1; b = 1; c = 2;
X = linspace(0,a,Nx); Y = linspace(0,c,Ny);    
[X,Y] = meshgrid(X,Y); X = X(:); Y = Y(:);
TRI = delaunay(X,Y); %Simple Mesh
figure;
trisurf(TRI,X,Y,0*X,Rho_e,'edgecolor','k','facecolor','interp');
Capture.PNG
I'm currently trying then to create this plot for a 3D mesh of delauney tetrahedra as set up in the previous code. My current attempt looks like:
tetramesh(TRI,[X,Y,Z],Rho_e,'facecolor','interp');
view(2); 
axis equal; colorbar; xlim([0,a]); ylim([0,c]); zlim([0,a]);
Which results in the following error message:
Warning: Error creating or updating Patch
 Error in value of property  FaceVertexCData
 Number of colors must equal number of vertices 
> In defaulterrorcallback (line 12)
  In Oct8_3DFEM (line 56)
My guess is that I somehow need to manipulate my Rho vector from reprsenting individual elements to individual vertices. However for physical purposes it is important I find Rho_e first. The final image I'm searching for will essentially be a 3D projection of the 2D one attached above. Any thoughts, advice or other suggestions would be greatly appreciated

Best Answer

Manipulate with faceVertexCData property if you want to assing some colors
get(p)
    %%
    FaceVertexCData = [ (72 by 1) double array]
    %%
    Vertices = [ (169 by 3) double array]
Example
p1 = tetramesh(TRI,[X,Y,Z]);
set(p1,'facevertexcdata',jet(numel(X)),'facecolor','interp');
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