THE DIRECTOR'S CUT
Visual Effects, part 1
Like every other aspect of post-production, we found visual effects to be complicated, technically challenging and time consuming. We thought, “Gee, we’ll just hand this off to a VFX studio and just get back a final product.”
Didn’t work out that way…
For starters, we had to deal with outputting the frames from the original data source to a format that the VFX folks could work with. Should have been simple, it was not. Our visual effects editor, “Spike” wanted the frames in a format known as “open exr” the industry standard for adding effects. Our film editor, “Gib” felt that Spike should take the original format and do the conversion. Emails went back and forth with no resolution in sight. So “Dan” the director, besides now working full time on the sound edit, became a visual effects supervisor.
Essentially, I had to convert from the raw data to the open exr format. Sounds rather straightforward, right? Almost. The process involved first importing the clip into Adobe Premiere Pro, then exporting to After Effects which supports the exr format. It took several hours of trial and error to get the resolution, color depth and aspect ratio to be consistent with the original format.
Then, we had to deal with file sizes. Each exr frame came in at 200 megabytes. Thus, a three second clip at 24 frames per second comes out to 14.4 gigabytes! We had 60 clips that ran as long as 15 seconds to deal with and bandwidth and storage became an issue. We could only upload several clips in a day as to not exceed data storage restrictions.
Okay, we got past that hurdle only to discover when Gib reinserted the final VFX clips back into Blood Pledge, the timing was off. The clips were too short, leaving these black gaps in the movie.
Again, we had to interrupt VFX production to solve this issue. Turns out open exr seems to prefer a 30 frame rate. We shot Blood Pledge in cinematic 24 frame. I assumed After Effects would follow the native frame rate of 24—No, of course not. Even after we discovered this bias, the clips were still coming back too short.
Turns out a “frame” to a computer can be quite arbitrary. Unlike real film which has fixed images, software can interpolate as many frames as it likes in one second. So Spike’s team had to adjust their software as well because VFX software also prefers 30 frames per second.
Now that we had the technical issues solved, it was time to output the visual effects. In next week’s blog, I’ll discuss the new challenges with creating the final image.
You can find out more about open exr here.
Blood Pledge had over 20 effects, you can check out the results here.