Computer and Machine Vision by Davies E. R

Author:Davies, E. R.
Language: eng
Format: epub
ISBN: 9780123869913
Publisher: Elsevier Science
Published: 2012-02-29T16:00:00+00:00

17.11 Perspective Effects in Art and Photography*

An artist is painting a picture somewhere on the countryside. Every now and again he looks up from his easel and surveys the scene, then he turns back to his picture and adds a few more touches. He has chosen his location carefully, and has set his easel at the right angle for best effect. We will suppose that he is not aiming to be impressionist, but wishes to present the scene as he sees it. Although his painting is in 2-D, he is able to present all the information needed for others to perceive the scene in 3-D. However, there is a problem. The picture needs to be viewed from precisely the right angle and distance that must correspond to the artist’s original viewpoint. Of course, the artist had to rotate his head and mentally rotate the scene between the moments that he viewed it and painted it (he had to do this because the canvas he was painting on was opaque: other artists such as Canaletto have used camera obscura methods to overcome this difficulty). However, we can overcome the problem by temporarily assuming that the canvas is transparent, which significantly simplifies the geometry (Fig. 17.18).

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