Photo #40

This is a photo of the then new Birmingham tram route along Bull St that I took some time ago. I was trying out my new 55-300mm lens and I liked the way that the tram was foreshortened and also the reflections in the buildings in the background.

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Model Pig Photogrammetry

Many years ago, while digging in the garden my father came across a small metal model of a pig ( left ). We weren’t completely sure of its origins but figured that it was some sort of promotional model. At that time there was a small group of shops near to my parents’ house, one of which was a butcher’s shop and we decided that it had probably come from there.  It was obviously quite dirty when we found it but a quick wash and a spray of black paint made it a lot more presentable. I think that one of my father’s friends made the wooden plinth for it. There is some text embossed on the side which is hard to read but it says “Agent for March & Baxters famous ????”. Marsh & Baxters were a well known meat processing company in Castle Bromwich, Birmingham, UK. and so I guess that the ???? used to say “sausages” or “bacon” 🙂

The pig sat in my mother’s house for years and recently I decided that it might be an interesting photogrammetry exercise. Although it’s largely matt black I felt that there was enough texture on the surface to give the photogrammetry algorithms enough to work on. I did the usual setup in the light tent and, using openMVG and openMVS the end result is pretty good:

Photogrammetry Notes

1. I normally try to take 4 sets of photos in 10° steps all round the object with each set being at a different height. Here I found that photos taken too much above the top of the pig, looking down, didn’t match at all. I’m not entirely sure why this is but fortunately the three sets were enough for a good reconstruction ( left )

2. The pig currently sits on a plinth but I think that it originally had some sort of mount under the centre of its belly. This is long gone but there are some remains that seem to hint that this was the method. I wanted to get the all the details of the underneath so I fashioned a method to support it using a nail inserted into a small hole drilled into the original mount ( right ). This worked very well and was surprisingly stable.

3. The dense reconstruction was very good straight out of openMVS ( left ). Most of the extraneous artifacts were not connected to the model so were easy to remove. The only two that needed editing of the model were, obviously, where the mount joined the body and a small patch on one of the forelegs. I used Meshlab for all the edits and to reduce the mesh size to fit in with the Sketchfab requirements.

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