Question: I have an origin point and a normal vector and wish to determine three points to create a reference plane. How can I calculate the third point using normal and origin?
Answer: This is very elementary geometry. If you have an origin point and a normal vector, you can easily calculate three points in a plane. Conversely, if you have three points in a plane, it is easy to calculate the normal vector.
Let 'x' denote the vector cross product.
Given an origin point P and a normal vector N:
Given three points P, Q and R in the plane:
I published a number of posts demonstrating this. The most useful ones for you might be the ones describing the GetCurveNormal method: