Now we come to the time-consuming part of the process: the triangular mesh. There’s no secret trick to this – you need to do it by hand. Why? Because your brain is better than any script or automated process at determining the contours of the face.
Here are some guides though. Small parts require small triangles. Never make quadrilaterals – they just look wrong. Stick to triangles. It’s easier if your subject has has a straight nose like me. Rounded noses are fiddly.
Create your mesh using a small brush on an empty layer above the image. Use a light colour that contrasts with the portrait. I prefer blue or green, since these are are two colours your subject probably hasn’t got in his or her face (unless they have a tattoo of a praying mantis on their neck).