# A matter of perspective

Have you ever watched rugby matches on TV and noticed the advertisements on the field that looked 3-dimensional? I remember having the impression that the adverts were superimposed by the TV people. But when I told the wife, she plainly pointed out that when the players ran across the field, their bodies covered the ads and not the other way round.

An example of the 3D ad (image from here.)

That was years ago but I was reminded of this when I read “How to Take a Penalty: The Hidden Mathematics of Sport” by Rob Eastaway and John Haigh. To achieve the 3D effect, the ads people made use of projective geometry and drew the ad in such a way that it looked like 3 dimensional. The best image I can find is this plan view from google maps. Notice how the top of the rectangular shape is longer than the bottom.

BTW, the book I mentioned is quite a good read.

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### One Response to A matter of perspective

1. Mikael Vejdemo-Johansson says:

You can often (not always) see this when you watch matches and get to see one of the secondary cameras sweep over where the ad is painted — they are all clearly built to work well with the camera booth for the primary cameras; when the action is seen through secondaries, you can get quick glimpses of heavily distorted (from the wrong perspective) ads.