Prime Focus handles conversion for 'Gravity'
Issue: November 1, 2013

Prime Focus handles conversion for 'Gravity'

LOS ANGELES — Prime Focus World ( recently contributed to Warner Bros.'s successful outer-space feature Gravity, staring Sandra Bullock and George Clooney.  The studio served as the exclusive 3D conversion partner on the film, which was directed by Alfonso Cuaron. 
Here, Prime Focus World's senior stenographer, Richard Baker; SVP production, View-D and VFX, London, Matthew Bristowe; global technical supervisor, Rajat Roy; and global head of View-D pipeline, Eoin Greenham, detail their work on the feature.
Post: What role did each person play?
Richard Baker – Senior stereographer, Prime Focus World.
Worked with director Alfonso Cuarón and stereo supervisor Chris Parks to develop the look of the depth for Gravity, and supervised the 3D conversion.

Matthew Bristowe – SVP production, View-D and VFX, London, Prime Focus World.
Key studio contact; managed the production team and the considerable production management requirements of the project.

Rajat Roy – Global technical supervisor, Prime Focus World & Eoin Greenham – Global head of View-D pipeline, Prime Focus World.
Headed up the technical team that built the unique pipeline for Gravity, including the close collaboration and integration with Framestore.

Post: Tell us about the working relationship with Framestore?
Richard Baker: “We have a great working relationship with Framestore, and early meetings with Nikki Penney (executive producer, Gravity) and Tim Webber (VFX supervisor) allowed us to ascertain what assets were available, what assets we could share, and how we were going to approach certain technical challenges that we anticipated. We were dealing with various types of shots on Gravity – (1) full conversion shots, (2) conversion of plates into which Framestore was to add stereo CG elements to the live action, and (3) shots provided by Framestore as 2D comps with VFX elements in.”
Rajat Roy: “Due to the nature of the show, and the immense complexity of the sequences, we knew that we were going to be working on ‘live’ shots, and that there was going to be a lot of passing work-in-progress shots back and forth between Framestore and ourselves. Framestore was rendering stereo CG elements to be dropped into our converted plates — floating pens, straps, etc., to sell the effect of weightlessness inside the capsule — but the VFX was not locked when we were converting the plates. In order to ensure that the stereo rendered CG elements matched the conversion exactly, in terms of their volumetric properties, we created highly accurate stereo camera pairs that we then passed back to Framestore — allowing them to render their CG elements using our cameras, and drop them straight into our converted plates. Creating these new stereo rigs required a huge amount of mathematical effort, and entirely new mathematical modeling that was unique to this show.”

Eoin Greenham: “Another interesting part of the collaboration was our use of VFX assets in the conversion process. We used LIDAR scans of the capsule sets, and cyber-scans of lead actress Sandra Bullock’s head from Framestore to produce depth mattes, and to model early stereo ‘design frames’, with a view to producing a ‘technically exact’ stereo image as a starting point for the conversion. But even this was not without its technical complications. Because the crew was dismantling and reassembling the set around the mono camera as it moved through the tight confines of the capsule set in its long takes, the LIDAR was not completely accurate. We had to rebuild the environment in order to produce the depth mattes, which we could then use to ensure the accuracy of the conversion, and a consistency of depth across all our shots.”
Richard Baker: “From this ‘technically exact’ starting point, I worked with Chris Parks to develop the look of the converted stereo shots, manipulating the stereo in both the characters and the environments to produce a more pleasing stereo image.”
Matthew Bristowe: “Framestore was the primary VFX partner — Prime Focus World was the exclusive conversion partner — and the collaboration between our companies was key to delivering an absolutely incredible creative and technical achievement.”
Post: What were some of the challenges and unique experiences of working on the film?
Matthew Bristowe: “Anyone with an interest in filmmaking is familiar with the long seamless shots that Alfonso and cinematographer Emmanuel Lubezki created for Children of Men. On Gravity, Alfonso and Emmanuel have gone one step further. The long, unbroken, floating camera shots work spectacularly well in space, and led to us producing the longest continuous shot that I believe has ever been converted – 15,531 frames, or 10 minutes, 47 seconds.”
Richard Baker: “That length of shot is a huge challenge in any VFX process, but when you factor in the assets that we use in conversion, it is pushed to another level. The size of the Maya files, the Nuke and Fusion scripts, the sheer amount of roto, the amount of clean-plating required to remove the characters from the environment – for 3K sequences up to 11 minutes in length — these factors all add up to huge file sizes and unprecedented render times. In order to handle these longer shots, we not only augmented the pipeline with pre-comp techniques to make the work more manageable, but also broke these shots into shorter sections to parallelize the efforts of the artists, with a keen eye on the ‘joins’ where the artists’ work met, to ensure consistency to the depth.”

Eoin Greenham: “We realized immediately that asset tracking was going to be complicated — and of course hugely important — on this show. Prime Focus World and Framestore were sharing a wealth of information, and both companies use proprietary formats and tools, and various third-party tools and plug-ins. It was important that our pipe tools understood their assets, and vice versa. But also, due to the live nature of the work, any amends to a shot by Framestore had to be reflected in the assets we were using in the conversion, to ensure that our pass back was built using the latest versions. Production management was a considerable task, but we solved this early through a close and open collaboration with Framestore.”
Rajat Roy: "A further challenge was keeping all of these assets live on our servers. Alfonso is a visionary director, who builds his narrative by keeping his options open as late as possible, to ensure that he is using the best shots to support the emotional arc of the film. This makes things difficult — especially in a dual-pipeline like the one we were building — because shots don’t get finalized until a late stage in the process. We had to keep all our work in a flexible manner, so that shots could be changed, amended or reverted as the cut came together — and this means keeping a lot of assets live, with all the storage implications this brings.”
Post: How long was the process?
Matthew Bristowe: “We started talking to Nikki Penney and the rest of the Gravity team towards the end of 2010, just as we were completing the conversion of The Chronicles of Narnia: The Voyage of the Dawn Treader. Our final deliveries were in November 2012. But this show wasn’t about the time, or the money. This film is a game-changer – both in terms of 3D and in terms of filmmaking. It’s one of those movies that you’ll look back on later in your career and be extremely proud to have worked on.”

Post: How many shots were provided by PFW?
Richard Baker: “Prime Focus World delivered 85 final shots for Gravity — which may not sound like a lot, but when you consider the length of some of the shots, we’re talking almost 30 minutes, or one third, of the show. This was the most complex, most creative, most technically challenging, and most rewarding conversion that I have worked on, and I’m delighted that Alfonso chose Prime Focus World to deliver his 3D vision.”