title: xtk volume rendering with .vtk file created from matlab
body: <p>I am beginning with XTK. I would like to load a .vtk file in order to make volume rendering into XTK.</p>
  
  <p>This .vtk file has been created with a matlab function which saves a 3D data array (voxel) into vtk format :</p>
  
  <pre><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
  </code></pre>
  
  <p>Once the <code>'output.vtk'</code> file is created, I try to load it this way :</p>
  
  <pre><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();
  
  };
  </code></pre>
  
  <p>But nothing displays in the browser.</p>
  
  <p>Is my 'output.vtk' is not a valid .vtk file for volume rendering ?</p>
  
  <p>How to load into XTK this kind of file ?</p>