I did some work on linear perspective in Drawing 1 and that helped me to grasp the basics of the vanishing point and horizon line so I now feel much less wary of this topic!
My Drawing 1 tutor recommended a book ‘Perspective for Artists’ by Rex Vicat Cole which I bought and have just pulled off the shelf. I feel like putting it straight back as it is 300 virtually impenetrable pages – maybe that is because it is an unabridged, unaltered republication of the original 1921 edition. Perhaps I will come back to it when feeling more patient or if I get well and truly stuck later down the line, which I might.
A short precis of the OCA Drawing 1 workbook notes on this topic seems to be a reasonable way to revise this topic as they were clear and helpful:
Linear perspective can be explained by picturing a door opened away from you. First, look at it straight on, so that the closed door and its door-frame are perfect rectangles. Now get someone to open the door slowly. As soon the door is opened even a fraction, it appears to become a different shape. It is no longer a rectangle, it no longer fits the doorframe and it has become reduced in size. Now look again at the open door first from a sitting position and then standing, the door will appear to be a different shape from each position as in the figures below.
This demonstrates the two basic principles of linear perspective. The receding parallel lines (in this case the top and bottom of the door) when extended meet at a point; secondly, the point at which they meet changes if you look at them from different heights. This is because the eye level horizon line shifts.
The horizon line divides your line of vision. The horizon line is directly in front of you even when you move and is also referred to as your eye level.
The vanishing point is an imaginary point on the horizon line to which all lines, above and below the horizon line, meet. These are not real lines but lines that if followed through in your mind from any object, will converge at the vanishing point.
All objects above the horizon line appear to have lines that angle downwards towards the vanishing point. All objects below the horizon line appear to have lines that angle upwards towards the vanishing point.
Looking back at my blog, I am reminded that when tackling the parallel perspective exercise of an interior view (see right)II had some difficulty in coming to terms with the fact that what your eye thinks it sees isn’t what you need to put down on paper in order to capture the perspective. I found that to get to grips with the compression of objects in the receding distance (the foreshortening) I needed to do some measuring because I couldn’t trust my eye alone. Each time I was surprised at just how compressed the objects need to be, the radiator and curtains, for example.
So what I’m say to myself is “don’t wing it, measure it!”