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Dr Ian Plummer

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Technical
Scale and Videoing Croquet Matches

There is a lot of interest in having significant croquet matches available on video.  This short note demonstrates the problems of very small hoops and balls on a very big court.

As part of another project I produced an accurate 3-D representation of a croquet court, which can be orientated and zoomed with the mouse.  What was instantly apparent was how dismal the court looked with real-size court furniture (i.e. peg, balls and hoops). 

3D lawn furniture scale x3
Court furniture at scale 1x

3D lawn furniture scale x3
Court furniture at scale 3x linear

Assuming that a web camera can be levitated over a croquet court (helium balloon, octocopter, trained kestrel... ) what sort of resolution is needed? And is it worth doing?

Web cameras are available typically at '720p': 1280x720 pixels (16:9). A croquet court is 1260 x 1008 inches (35 x 28 yards, 5:4). Consequently we are looking at one pixel = ~1 square inch. Thus balls and hoops are just 3 pixels wide! Even, however if the resolution of the camera is excellent, if you can see the court, the balls and other features are very small unless you have an immense display; aerial shots of the whole court are pretty useless. See the Appendix for modelled aerial shots.

Lawn with eye 6 feet above lawn
Scale x1 with eye height at 72" standing back 11 yards from South boundary

From the same arguments a roving camera beside the lawn is only going to show detail for things happening nearby. Above I have put the camara at head height and moved back to get in most of the lawn. Hoops 2 and 3 are near invisible. The perspective control of the virtual camera has some effect in making the remote hoops look small.

The conclusions are:

  • There is little utility in getting a 'full court' view either from above or from the side. The scale of the hoops and balls are too small to be seen at distance.
     
  • For detailed shots cameras would need to be at the closest point on the boundary to the action and hence need to move around. Whilst distant action could be viewed with a zoom lens, holding the camera still becomes a problem.

 

Appendix

The following series of pictures show a standard size court with the hoops, peg and balls scaled linearly by x1, x2… x6.  They give an indication of the scaling needed to produce useful diagrams and animations. Click on the images for full size. The modelling uses a perspective camera hence there is slight pin cushion distortion.

Lawn with furniture real size
Scale x1
Lawn with furniture x2
Scale x2
Lawn with furniture x3
Scale x3
Lawn with furniture x4
Scale x4
Lawn with furniture x5
Scale x5
Lawn with furniture x6
Scale x6

The yellow ball was animated hence it does not appear in the same position on each picture.

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Updated 28.i.16
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