Rotoscoping is the process of tracing over footage, frame by frame, in order to create a matte to be used as an element for compositing over another background. Think of it this way; say you have a three second video clip of a golfer hitting a ball. If you wanted to place that golfer on an alien planet, or deep underwater, playing a round of golf, then you would need to go frame by frame tracing around the golfer swinging his club and then composite over the new background. Rotoscoping is a time intensive process. With the example of the three second video clip of the golfer, at the standard rate of 24 frames per second, that means you would need to rotoscope 72 frames to complete the sequence. In the past, I’ve showed you how to use the rotobrush in After Effects. However, with longer sequences, it’s better to use a dedicated roto program such as Silhouette FX. In this tutorial, I am going to show you the basics of roto with Silhouette FX in two simple steps:
– Breaking the image down into Shapes
– Moving Shapes throughout the Sequence
*Before we begin, if you need help setting up your shot, or need some initial background on Silhouette FX, I would recommend you refer to a previous tutorial I posted titled “Creating an Alpha in Silhouette FX” which you can review here.
BREAKING THE IMAGE DOWN INTO SHAPES
Once you import your media and setup a new session, you will need to select your spline tool from the left hand side of the canvas window. Your options are B spline, X spline, or Bezier. Please note that if you intend to import the roto’d footage into NUKE for compositing, then you will want to avoid using the X spline tool as there seems to be issues with NUKE interrupting those particular splines. I would recommend going with the B spline in that instance.
Whichever tool you decide to use is up to you, however, the technique is universally the same. A successful roto is built upon breaking the image down into a series of shapes. In this example of a video clip of some hands, I will focus on the left hand first and break down each finger into a series of ovals and curves that contours around the joints.
This is because as the video clip progresses and the hand begins to move and flex, moving individual shapes located around the anatomical joints is much easier than trying to create one large outlining shape around the entire hand and trying to move that frame by frame. It doesn’t matter what the roto subject is – a hand, a face, a machine, a book – it is your job as the roto artist to visually break down the subject into a series of shapes and animate those shapes over the course of the footage.
MOVING SHAPES THROUGHOUT THE SEQUENCE
At the bottom of Silhouette you will see the TIMELINE. This is where you will be able to visually see all the keyframes and movements you are making with the shapes throughout the sequence.
Here are the playback controls:
X – Move one frame forward
Z – Move one frame backward
L – play video forward
K – pause video playback
J – rewind video playback
You can also zoom in and out of your image with ‘I’ and ‘O,’ and SPACEBAR allows you to pan around the image as needed.
As you move forward frame by frame you will not be using the X spline or Bezier tool to move the shapes you created. Instead, you will be using the Transform tool or the Reshape tool:
T – transform Tool > creates a box form around your shape allowing you to manipulate the corners of the box in order to stretch and form the shape. This is ideal for most simple movements between frames. The more basic movements you make, the less chance there is for “jitter,” which is an anchor point from one of your shapes jumping around from being manipulated wrong throughout the sequence.
R – Reshape Tool > this tool allows you to manipulate the individual anchor points of each shape. This should be a last resort method of moving a shape and only needs to be used in shapes that have extreme changes that cannot be captured using the transform tool. An example would be an article of clothing where a wrinkle appears for a few frames and then disappears.
To summarize, you will be using the X and Z keys to move forward and backward one frame at a time and using the Transform tool to move the shapes to capture broad movements, or the Reshape tool to capture fine details. Once your finished, use the J,K, and L keys to playback the footage and watch the shapes to make sure they stay on track with the roto subject. If there is an issue, simply stop the play back and make the adjustment as needed.