Here is a demonstration
of a constructive
drawing technique,
without the use of a camera
or computer. As been applied in
early paintings. Understanding
the illustration from A. Dürer
makes you aware of the
possibility to move
the drawing pane
behind the object.
Also using a light for
projecting a perspective
shadow, instead of
using a thread and screw/eye.
Measuring
height and width
can be done in the map
of the floor and wall,
both flattened. As also
the projection wall.
The most effective are
the V(anishing) points,
which can be constructed with
parallel radiants out
from center eye point O.