I drew an interior doorway within my home just using my eyes to judge perspective initially. This was done using a black ball point pen – line drawing only. Once I was happy with the drawing, I drew in where I thought my eye level was, on the actual drawing. I used this to draw a horizontal line across the page (drawn in blue ballpoint pen) from which I then checked the perspective using a ruler and pencil.
I checked the perspective of the door, the interior corners of the door frame and the vertical lines of the floor boards. I found that the upper part of the drawing was more accurate than the lower (apart from the floorboards which were totally off!), which is interesting, I wonder if this is partly because to look at the bottom half required adjustment of my eye line?
I re-drew the parallel lines in red ballpoint where appropriate and comparing this with my original indicates that I wasn’t too far off. It also showed that because of the angle of the door there were 2 vanishing points (one where the interior door frame angles and horizontal floor board lines meet and the other where the door angles meet) which threw me a bit for a while, but worth bearing in mind for future reference.
Below is the drawing with all amendments.
Deborah McAulay 