Calculate the normal for the 'facet normal' in STL file format

Question

So I have my STL code and I have been putting the normal as 0 0 0 for each triangle, as you can imagine this means that only certain software can utilise the code.

What is the method for working out the normal

i.e. the vector maths

Hookup

Answer 1

You should take vertices of the outer loop and calculate surface normal as described here.

Asti