Playground - Sand and Sky: finding the detail to track

Some shots are easier to track than others. A lot of straight edges, corners and obvious contrast make choosing features straightforward, even with an ordinary tracker. But how do you find points to track when the frame is full of nothing but sand and empty sky?

This was the problem facing Paal Anand and the team at Los Angeles based Playground when they started work on a promotional film for the Saudi Arabian environmental agency NADEC.

boujou's ability to track organic textures that defeat other matchmoving applications is renowned, but the searing dunes and flat sky of Namibia presented a special challenge.

One shot filmed from a helicopter exemplified the difficulties, according to Anand: 'The shot was mostly sky and contained very little ground detail. On top of that there was a very flat tone from the telecine, so there was really nothing to lock onto to get a good track.' The solution? Enhancing the contrast of the footage by colourcorrecting it to exaggerate edge information before tracking the shot with boujou. 'Effectively we created a tracking plate,' Anand explained, 'and the enhanced detail was enough to give boujou something to work on in an otherwise featureless scene.'

'The extra horsemen, CG helicopters and banner were all added in post,' Anand explained. 'The promo was originally planned at 60 seconds but the client extended it to 120 seconds late in the project schedule: that gave us a lot of work to do in just one week from getting the plates to our deadline. All the workstations were tied up during the day, leaving no time for tracking work. Being able to batchqueue the shots to track automatically overnight with boujou was just what we needed.'

'We had a very limited time scale on this project so it was crucial that we could work on other things while boujou did the tracking automatically. Speed is the key and boujou is fast and very accurate. In the past with other matchmoving software you were lucky to get 80% towards a good track and even then you still had to finish the job by eye.'