cavity.f

It is done in the following way:

• determine the cavity for the new node
  • start from the base element
  • add elements one by one through adjacency; only element whose circumcircle enclose the new node are taken into account
  • check for nodes within the cavity; if any, remove the element to which they belong from the cavity
  • check that the cavity is convex in the sense that each cavity face is visible from the new node, else the element bordering the face is removed from the cavity
• remove the cavity elements
• create new elements connecting the new node with each of the cavity faces
• if any element has a very small volume or at least one very small height the original mesh of the cavity is restored
• since elements have been deleted and created the base element numbers of the nodes still te be inserted may not be correct any more: perform a check on these nodes and correct the base element numbers if necessary.