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Monday, March 19, 2012

Here is another technical test for the whole POVCam style.

This one is about 3D motion tracking - or how to add or remove objects from a point of view shot.

When you have complex motion - a camera moving in every direction and facing anywhere - it can become hard to do even the most basic of post production. Some effects, such as matting out an object, are easy when you are on a tripod. But when the image is moving everything is much harder.

This test was an effort to put something false into a shot. Again, super easy if this had been a locked off shot.

For you technie fans here was the process...

  • Film at 50 fps to get more motion information
  • Use "Icarus" to reverse engineer the motion
  • Icarus can only use non-HD footage so I give it an downscaled version of my master to work with
  • Export that camera movement data and import it into After Effects
  • Now the virtual camera in After Effects moves the same as the real camera did
  • As Icarus used a downscaled footage I bring in the HD footage again but have to adjust the virtual camera lens angle to compensate. I know my cameras field of view is 59 degrees so I enter that myself.
  • Add a 3D layer for the object that is needed in the scene. In this case the big comedy Google Maps arrow
  • Put it in the right place in the virtual world
  • Render the footage, but back at 25 fps to match other material

The render is quick fast, the Icarus part very slow, perhaps a couple of hours.

I quite like it in the end. I may try and sneak something like it into the feature film.

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