Problems when performing the trunc operator in 3d

General Discussion
1

Hello FreeFem community,

A few weeks ago, I posted a question about defining adjacencies in a 3d mesh. Also I asked how to assign logical values to each element using a P0 fespace function in 2d. Both cases were implemented succesfully in 2d. However, I found difficulties to assign logical values to 3d elements according to the criteria of number of adjacencies.

When I use this logical function to remove tethrahedra according to the trunc operator, it reaches a certain point that they dont remove any elements at all, although there are still some tethrahedra remaining. This situation doesnt happen in 2d since the algorithm could remove all the elements.

I have created a output file text where you can see after 11 iterations, that the number of elements remain stable until the end of the execution.

Number of remaining elements accumulated disolved volume

         71331                                                        167.531             
         61523                                                        456.471             
         49101                                                        841.763             
         36141                                                        1268.32             
         27109                                                        1585.53             
         23390                                                        1723.45             
         22440                                                        1759.66             
         22128                                                        1770.23             
         22022                                                         1773.76             
         21979                                                          1775.2             
         21964                                                          1775.69             
         21957                                                          1775.9             
         21957                                                          1775.9             
         21957                                                          1775.9             
         21957                                                          1775.9             
         21957                                                          1775.9             
         21957                                                          1775.9             
         21957                                                          1775.9             
         21957                                                          1775.9             
         21957                                                          1775.9

Here you have attached the link with the .edp code and .mesh file

https://1drv.ms/u/s!AqQdZogsFfj9gbFR3c8mjKjF5MjLHw?e=HwetCO

Any suggestion would be very appreciated.
Best regards
Jacob

2

When I had tried using the last mesh generated as a input in the same code, I saw that the trunc command started to work again. Why did this happen? Is it due to the difficulties of the program to handle the resultant non-manifold meshes?

Regards