3D interface constructed by Delaunay triangulation (16 cases)
<table width="800">
<tr>
<td>  <img border="0" src="blk_3d_case_0.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_1.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_2.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_3.jpg" width=200> </td>
</tr><tr>
<td>  <img border="0" src="blk_3d_case_4.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_5.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_6.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_7.jpg" width=200> </td>
</tr><tr>
<td>  <img border="0" src="blk_3d_case_8.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_9.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_10.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_11.jpg" width=200> </td>
</tr><tr>
<td>  <img border="0" src="blk_3d_case_12.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_13.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_14.jpg" width=200> </td>
<td>  <img border="0" src="blk_3d_case_15.jpg" width=200> </td>
</tr>
</table>