I am beginning with XTK. I would like to load a .vtk file in order to make volume rendering into XTK.

This .vtk file has been created with a matlab function which saves a 3D data array (voxel) into vtk format :

Code :
  function savevtk(array, filename)
    %  savevtk Save a 3-D scalar array in VTK format.
    %  savevtk(array, filename) saves a 3-D array of any size to
    %  filename in VTK format.
        [nx, ny, nz] = size(array);
        fid = fopen(filename, 'wt');
        fprintf(fid, '# vtk DataFile Version 2.0\n');
        fprintf(fid, 'Comment goes here\n');
        fprintf(fid, 'ASCII\n');
        fprintf(fid, '\n');
        fprintf(fid, 'DATASET STRUCTURED_POINTS\n');
        fprintf(fid, 'DIMENSIONS    %d   %d   %d\n', nx, ny, nz);
        fprintf(fid, '\n');
        fprintf(fid, 'ORIGIN    0.000   0.000   0.000\n');
        fprintf(fid, 'SPACING    1.000   1.000   1.000\n');
        fprintf(fid, '\n');
        fprintf(fid, 'POINT_DATA   %d\n', nx*ny*nz);
        fprintf(fid, 'SCALARS scalars float\n');
        fprintf(fid, 'LOOKUP_TABLE default\n');
        fprintf(fid, '\n');
        for a=1:nx
            for b=1:ny
                for c=1:nz
                    fprintf(fid, '%d ', array(a,b,c));
                end
                fprintf(fid, '\n');
            end
        end
        fclose(fid);
    return

Once the `'output.vtk'` file is created, I try to load it this way :
Code :
    window.onload = function() {
 
    var r = new X.renderer3D();
    r.init();
 
    // create a mesh from a .vtk file
    var skull = new X.mesh();
    skull.file = 'output.vtk';
 
    // add the object
    r.add(skull);
 
    // .. and render it
    r.render();
 
    };
But nothing displays in the browser.

Is my 'output.vtk' is not a valid .vtk file for volume rendering ?

How to load into XTK this kind of file ?