Mark Fry

[ VFX : Asylum Matchmove ]

 
 
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Asylum Matchmove
07 June 2011

Urban exploration guerilla filmmaking

I am currently working with a group of very talented CG & VFX Soho artists on a pitch for an independent film. I shot these background plates on my Canon 550D/T2i in an abandoned Asylum located in South London.

The plates were delensed in Nuke, camera tracking was done in PFTrack and final adjustments to the camera's f-curves were sorted out in Maya. I modelled some proxy geometry in Maya to gauge the quality of my camera solves with a checkerboard render composited over the plates in Nuke.

The second-to-last shot (with the cone) in the above video proved very difficult to track and solve given the wild handheld camera move, 180 degree shutter speed and its associated motion blur. I was able to get a mediocre camera solve for 1/3 of the shot duration and manually matchmoved the rest of the shot in Maya.

 

 

 
   
 

 

[ click for full-size ^]

Manual matchmoving in Maya

Sometimes you can only take a camera solve so far in the tracking software and you may need to finish it off "manually" in your 3D application. Inspired by the camera f-curve editing in PFTrack I developed a similar workflow in Maya.

I have dual monitors so I can have a fullscreen Maya camera window on the right monitor and six Graph Editor windows on the left. Use Panels > Tear Off Copy to spawn all the extra Graph Editor windows.

Using the Graph Editor and editing the f-curves gives you a very fine level of control when making adjustments to the camera, much finer than using the Translation & Rotation Tools. I found that there is a relationship between movement on certain axis and therefore stack my f-curve windows as seen in the image above.

  • Translate Y and Rotate X movements affect each other
  • Translate X and Rotate Y movements affect each other

While any movement will indeed affect the five other axis, I found those two relationships listed above to be the ones that I was mostly tweaking together. Rotate Y also has a great affect on Rotate Z but not as enough for me to re-arrange my windows.

I also found it quite useful to turn on these Camera Settings:

  • Safe Action
  • Safe Title
  • Film Origin

That extra bit of info displayed on the camera window gave me some static elements on the screen to help diagnose the changes in direction of the camera movement from frame to frame.

Finally, I find it very handy to set up some custom Hotkey assignments in Maya to step forward/backward by one frame while NOT affecting Undo/Redo.

Name PreviousFrame_noUndo
Hotkey ;
Mel undoInfo -stateWithoutFlush off;
currentTime ( `currentTime -q` - 1 );
undoInfo -stateWithoutFlush on;
   
Name NextFrame_noUndo
Hotkey /
Mel undoInfo -stateWithoutFlush off;
currentTime ( `currentTime -q` + 1 );
undoInfo -stateWithoutFlush on;

 

 
     
 

 

Copyright Mark Fry. All rights reserved.

Music used under CREATIVE COMMONS LICENSE
Music by: Kevin Macleod

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