View Full Version : Head Replacement( tracking problems)!

03 March 2004, 11:36 PM
Hello everyone,
Software: Shake 3.0
I am doing a head replacement. The first 150 frames or so there is motion motion blur just a simple track to get the head to track in. After that 150 frames the object that I need to attach the head to turns away from camera very fast and all the tracking spots that I have are gone. MOTION BLUR. Are there any work around tricks to tracking a motion blured shot.

I was wondering how you hand track an object in. How is that done in shake. Reason being if I can't get a good track I will need to track the head in by hand. If someone could explain the process to hand tracking in shake that would be great.

Thanks for all the help in advance


03 March 2004, 02:27 AM
Ok so I have tried setting keyframes every 10 frames and useing (perdict location from next keyframe, setting in the tracker. It worked ok but not great. Are there any other ways of doing this.


03 March 2004, 12:25 PM
Do you only have keyframes every 10th frame? Sorry to state the obvious but you might need more keyframes :p

03 March 2004, 05:52 PM
Yeah it going to take a key frame every frame I think. The 10 frames was just for the tracker, so when it gets lost it looks for the next keyframe 10 frames or so(it a setting in the tracker node) away, kinda like a path to follow. seems to be working ok still doing some of it by hand. SLOW!

03 March 2004, 05:52 AM
To track the object by hand, you are basically setting transformation keys by moving the object and setting a keyframe. You might call it roto or matchmove then. Tips for doing this follow. Find a way to watch the sequence that you have to match through to see the characteristics of the movement (hopefully at full speed).

Stepping through the sequence frame by frame, making a note of the frames in which the object you are tracking hits extreme points in it's movement. For example, if the object starts off in the bottom left of screen at frame 1, moves to middle right by frame 20, then moves back to top left by frame 35 you would note frame 1, 20, and 35 as possible keyframes you would want to set first. If there are curved motions (likely), then you will also probably want to note frames where the object reached the apex of the arc.

When you keyframe your object, the idea is to block out majors motions first, then progressively refine. You will keyframe the largest motions first (frame 1, 20, 35) then go back and add the more subtle movements (apex of arcs and such).

Finally, use time splitting to progressively refine once you have keyframed the major and minor motions. For example, you have the minor motions down but the object still isn't quite in the right position between frame 5 and 15. So instead of setting the next keyframe at frame 6, then 7, then 8, etc until you get the object on track you would set a keyframe at frame 10, then check to see if things are on track. If not on track between frame 5 and 10, you would set the next keyframe around frame 7 or 8. In general, if you split the difference between keyframes when choosing where to place a corrective keyframe, it will take you fewer keyframes to get the motion done.

Bart Robinson

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