How did they make Voldemorts face in the Deathly Hallows?

Answer 1

Tom Riddle was known as Voldemort during his time at Hogwarts School to a few close friends. He essentially went through two transformations:

His first transformation was leading up to his first defeat when the protection charm backfired the Killing Curse he cast on Harry when he was a one year old. Up until this time he had created several Horcruxes each of which altered his physical features (for example: the white in his eyes being permanently blood red, and having a piece missing from his cheek).

His second transformation was after his resurrection when he appeared to be more serpent like than human. It is assumed that the injuries he incurred during the creation of his Horcruxes were some what healed after his resurrection due to them not being present. His soul however was still as damaged as it was over a decade before.

It is also assumed that his resurrection form is similar to his previous form as his followers appear to recognise him in the Riddle Graveyard. This is not specifically known however.

Answer 2

Voldemort's face was a combination of makeup effects and computer generated graphics. The color and texture were done by hand, but other items, like the removal of the full nose were done by computer.