Roto Tips

Creating usable shape animations can be a bit tricky, the most common problem being edge chatter. Here are a few tips to help you on your way.

• Analyze the sequence. View your sequence to determine the frame that requires the greatest number of points to create the shape. It is easier to draw your shape on the most complex frame than to start on a simpler frame and add points later.
  
  
• Create shapes with fewer points. Use as many points as needed to create the shape, but avoid using more than necessary. The fewer the points, the easier it is to successfully animate the shape. Unnecessarily complex shapes are inevitably difficult to edit.
  
  
• Create multiple shapes. Draw multiple shapes and combine them into complex roto objects. Drawing separate shapes for the major parts of an object gives you finer control over motion, especially when separate objects intersect each other.
  
  
• Edit the shape in groups. Try not to individually move points in a shape unless absolutely necessary. Moving points in groups will maintain consistency and eliminate edge chatter.
  
  
• Keyframe, keyframe, keyframe. When you edit your shape at various frames in the sequence, Shake animates the shape between those keyframes. This saves you work. Make as few keyframes as possible, but include enough so that the shape properly follows the object that you are rotoing. For instance, on an 80-frame clip, start by adding keyframes at frames 1, 20, and 40. If more animation is needed, add keys at frames 10 and 30. Get the idea? Creating too many keyframes will cause the shape to jitter or chatter.
  
  
• Use a tracker. A Tracker, which is a node that analyzes the motion of a clip, can be attached to a shape or selected points. The motion from the Tracker is used to animate the horizontal and vertical positioning of the shape or point. It sure beats animating frame by frame. To attach a Tracker to a shape, right-click the shape transform control and choose Attach Tracker to Shape. To attach a Tracker to selected points, right-click one of the selected points and choose Attach Tracker to Selected Points. This calls up a list of pre-created Trackers for you to choose from. Tracking is covered in Lesson 7.