Hi everyone!

I’m experimenting with the HPRefinement function in Netgen.

In particular, I’m trying to construct a Powell-Sabin split. To achieve this I’ve constructed a new refinement reference triangle, i.e.

```
int reftrig_Powell_splitedges[][3] =
{
{ 1, 2, 4 },
{ 2, 3, 5 },
{ 3, 1, 6 },
{ 0, 0, 0 },
};
int reftrig_Powell_splitfaces[][4] =
{
{ 1, 2, 3, 7 },
{ 0, 0, 0, 0 }
};
HPREF_ELEMENT_TYPE reftrig_Powell_newelstypes[] =
{
HP_TRIG, HP_TRIG, HP_TRIG, HP_TRIG, HP_TRIG, HP_TRIG,
HP_NONE,
};
int reftrig_Powell_newels[][8] =
{
{ 1, 4, 7 },
{ 4, 2, 7 },
{ 2, 5, 7 },
{ 5, 3, 7 },
{ 3, 6, 7 },
{ 6, 1, 7 },
};
HPRef_Struct reftrig_Powell =
{
HP_TRIG,
reftrig_Powell_splitedges,
reftrig_Powell_splitfaces,
0,
reftrig_Powell_newelstypes,
reftrig_Powell_newels
};
```

Now the structure I get out is more or less correct, but I don’t understand why the edge splits don’t match across two elements.

Any ideas?