<h1>Results</h1>

The program execution produces a series of mesh files <code>3d_mesh_*.vtk</code>
that we can visualize with any of the usual visualization programs that can read the VTK
file format.

The following table illustrates the results obtained employing the normal projection strategy. The first two
rows of the table show side views of the grids obtained for progressive levels
of refinement, overlain on a very fine rendering of the exact geometry. The
dark and light red areas simply indicate whether the current mesh or the fine
geometry is closer to the observer; the distinction does not carry any
particularly deep meaning. The last row
of pictures depict front views (mirrored to both sides of the geometry) of the
same grids shown in the second row.


<table style="width:90%">
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.common_0.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_1.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_2.png" alt="" width="400"></td>
  </tr>
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_3.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_4.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_5.png" alt="" width="400"></td>
  </tr>
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_front_3.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_front_4.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_front_5.png" alt="" width="400"></td>
  </tr>
</table>

As can be seen in the pictures---and as we anticipated---the normal refinement strategy is unable to produce nicely shaped elements
when applied to surfaces with significant curvature changes. This is
particularly apparent at the bulb of the hull where all new points have been
placed in the upper part of the bulb and the lower part remains completely
unresolved.

The following table, which is arranged as the previous one, illustrates
the results obtained adopting the directional projection approach, in which the projection direction selected was the y-axis (which
is indicated with a small yellow arrow at the bottom left of each image).


<table style="width:90%">
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.common_0.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.directional_1.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.directional_2.png" alt="" width="400"></td>
  </tr>
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.directional_3.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.directional_4.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.directional_5.png" alt="" width="400"></td>
  </tr>
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.directional_front_3.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.directional_front_4.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.directional_front_5.png" alt="" width="400"></td>
  </tr>
</table>

The images confirm that the quality of the mesh obtained with a directional projection is sensibly higher than that obtained projecting along the
surface normal. Yet, a number of elements elongated in the y-direction are observed around the bottom of the bulb, where the surface is almost parallel to the
direction chosen for the projection.

The final test shows results using instead the projection normal to the faces:

<table style="width:90%">
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.common_0.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_to_mesh_1.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_to_mesh_2.png" alt="" width="400"></td>
  </tr>
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_to_mesh_3.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_to_mesh_4.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_to_mesh_5.png" alt="" width="400"></td>
  </tr>
  <tr>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_to_mesh_front_3.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_to_mesh_front_4.png" alt="" width="400"></td>
    <td><img src="https://www.dealii.org/images/steps/developer/step-54.normal_to_mesh_front_5.png" alt="" width="400"></td>
  </tr>
</table>

The pictures confirm that the normal to mesh projection approach leads to grids that remain evenly spaced
throughout the refinement steps. At the same time, these meshes represent rather well the original geometry even in the bottom region
of the bulb, which is not well recovered employing the directional projector or the normal projector.
