Question

projection point on plane" defined by parametric form along direction

Answer 1

The position of a point in engineering drawing is defined with respect to its distance from the three principle planes i.e., with respect to the VP, HP, & PP. The point is assumed to be in the respective.

Answer 2

A line is determined by a point and a direction. ... which leads to the parametric equations of the line passing through the point P_0=(x_0,y_0,z_0) and parallel to the vector v.