I can't create a Pipe 3D without annoying shrinkage in the corner of my bezier curve using bevel object. Those are my step. I create a bezier curve (on 3 axes) transforming two corner in Vector corner (to have a perfect angle)
I generate a circle and using bevel object I sweep the circle along the bezier (3d).
Easy...BUT I can't undestand how to solve the shrinkage in the corners. Other artifacts (such as compenetration) comes when instead using a Vector corner I use a normal (automatic) corner and model it in 90 degree shape.