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Drain the Oceans: Thai Cave Rescue – A Nat Geo documentary

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Drain the Oceans

Our CEO Roo Walters has been exploring and mapping caves for over 35 years. News of his endeavours, and Commendium’s reputation as intrepid explorers flourished. One particular exploration to China’s super caves can be seen online. Little did we know that Roo’s relentless pursuit of subterranean mysteries would attract the attention of a renowned television production company, MSPTV.  Mallinson Sadler Productions, asked Commendium to provide assistance for an episode of the ‘Drain the Oceans’ series on NatGeoTV. Commendium has previously worked with The National Geographic on several occasions. Working on the ‘Drain the Oceans: Thai Cave Rescue’ episode was a exciting welcome return to working together.

The Brief

Our brief was to 3D survey a 6 km stretch of the Tham Luang cave passages in Thailand, using LiDAR terrestrial scanners. The data from the scans would be processed to make a photorealistic CGI 3D model of the cave journey. The 3D model itself illustrates part of the Thailand Cave Rescue story deep in the Chiang Rai province.

Viewing the survey map Of Tham Luang

Prior to setting off we were looking at a hand-drawn cave survey map of the Tham Luang cave system, completed by its first explorers. Looking at the illustration it was immediately clear that this was going to be one of our more demanding projects, 6km of often narrow, invariably humid and muddy cave passages. We estimated it would take three weeks, to scan the caves and a complete surface survey of the area.

 

 

The Challenge

The cave system proved to be every bit as challenging as we had imagined. In the dry sections, the cave was very easy to navigate for experienced cavers, however, then came the slippery section with lots of clambering over large boulders. With each of us carrying about 20kg, the humidity was draining for the crew.

Scan Positions and Surveying

We opted to scan from the furthest point inside the cave and work our way through to the entrance. This was mainly for physical reasons, for every subsequent surveying day required less travel to the start and so became easier. Most days underground were more than ten hours.

Photography and Textures

A crucial part of the assignment was to record the cave textures. It is amusing to put one of the world’s leading caving photographers to such repetitive work, but the discipline to ensure everything is recorded meticulously, is probably the single hardest aspect of 3D data capture. We tried to work to three days and then rest on the fourth, however, in practise, our rest days and evenings were spent processing the vast amounts of scanned data. Our drone operator meanwhile was travelling above ground capturing the surface terrain data.

Capturing Data

By the end of the project we had gathered almost a terabyte of data, which takes some managing, but again, with our procedural disciplines in place we ensured we captured all the data required. We had loosely stitched 400 LiDAR scans together in the field, to check for any parts of the cave we may have missed, however, all was looking good. With all the data gathered, we found ourselves quite sad to leave Thailand at the end, having made many solid friends, it was a very emotional journey.

Back in the UK

Once back in the UK the real work of bringing the scans to life began. The photos were processed to colour-match and check level brightness. The scans were re-stitched and cleaned up to eliminate noise and unnecessary items. The scans were also adjusted with GPS co-ordinates, to ensure the cave would be orientated correctly when we merged both the surface scans and underground models. Meanwhile, we processed the drone imagery into a surface model. There were a few problems, as the conditions had been quite cloudy, but skilful low flying, cloud-dodging, and waiting for conditions to improve, meant that a superb model accurate to within 10 cm was produced.

The VFX Team

The next phase was working with the VFX (visual effects) team. Over several weeks we created several models to create CGI imagery for the film. We built an animated diver, constructed sections of the cave in meticulous detail, tested various animations and effects. The final result is superb. The broadcast of ‘Drain the Oceans: Thai Cave Rescue’  is available for viewing HERE

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