Let a line in three-dimensional space be given by two points A and B. The coordinates of these two points (in a Cartesian coordinate system) can be varied by using the input fields at the top right; integers from −5 to +5 are allowed. The buttons in the lower part of the panel are for controlling the projection direction.
The app draws a projection of the coordinate system and the line (black); a vector that determines the direction of the line is represented by the violet arrow. Below the drawing a vector equation (with parameter λ) is given.