Parallel vs. central
SŠ7 minWhen parallels stay parallel and when they converge.
What is happening
Every ray leaves one centre S. The farther the object from π, the smaller its image – which is why central projection does not preserve size.
Kind of projection
Scene
Spatial view
Theory
Depending on where the rays come from we distinguish two kinds of projection. In central projection all rays leave a single point S. In parallel projection they are mutually parallel – the centre is imagined at infinity.
The difference is not cosmetic. Parallel projection preserves ratios of lengths on parallel segments, so a drawing can be measured. Central projection does not – more distant objects shrink.
That is why engineering draws in parallel (Monge projection, axonometry), while architecture reaches for central projection where a lifelike impression is wanted – in perspective.
Step-by-step construction
Practice
Build the construction yourself
What is the next step?
1 / 5Choose the step that comes next. The drawing only advances on a correct choice.
Check your understanding
Where do the rays come from in central projection?
Which projection lets you measure straight from the drawing?
What happens to the image when the solid moves away from the picture plane in central projection?
Downloadable material
A PDF for this lesson is in preparation.
Need help?
Book a lesson and we will go through it together, step by step.