Once A Basic Shape Such As A Cube Or A Rectangular Prism Is Drawn Correctly It Can Become The Guide
The Basic Cube Can Become The Basis For An Endless Variety Of Objects 
And So Can The Basic Brick Shape - Look Around And See
The ties of the railroad and the black lines of the structure at the right are parallel to the picture plane; therefore they do not converge. The rails and the fancy lines of the structure are perpendicular to the picture plane; therefore they do converge, and since the observer's central visual ray points exactly in their direction, their vanishing point must be in the center of the picture. This is one-point perspective. Now look at the suitcase. Both sets of its horizontal lines are oblique to the picture plane; therefore they converge to left and right. The observer (top view) points in their direction to locate their vanishing points. This is two-point perspective.