Question regarding pixels outside a triangle, where the fragment shader is solely executed for the purposes of evaluating derivatives for use in non-helper fragment-shader invocations inside the triangle:
How are the interpolated varying variable values computed in those fragments? Do they use special barycentric coordinates not in range [0,1]? Or how is it possible to achieve varying values that still make sense (i.e. are continuous in relation to their adjacent pixel varying values)?
Clarification is very appreciated!