Scientific Rotoscoping : Scientific Rotoscoping in Maya

Some useful preparations before you start rotoscoping:

• Each object in Maya is moved relative to its pivot (A). This pivot is usually in an inconvenient location when imported from a CT scan. It is best not to change the CT pivot, but rather to create an animation pivot for rotoscoping. But if you wish to change the location of the pivot, select the translate tool (labeled C in image above), press and hold D on your keyboard and move the pivot, or select Modify/Center Pivot from top menus.

• To create an animation pivot, select Create -> Locator from the top menus. Move the locator to the point on/in the bone around which you would like it to pivot. Select the bone and then the locator. Press P to parent the bone (child) to the locator (parent). Now rotoscope by selecting the locator and not the bone. The locator will contain the animation curves for your bone.

• Remove the wireframe (green grid around the bone contours), go to Window -> Settings / Preferences -> Preferences -> Display. Select: Wireframe on shaded: none.

• Hot keys are W (translate) and E (rotate).

• Use Window/Animation Editor/Graph Editor to see 6 DOF animation curves (with your animation locator selected)

• Now lock the bone so you do not accidentally move it relative to the animation pivot.

  • Press button in farthest right top corner of the Maya window to open Channel Box/Layer Editor (if it is not already open)

  • Select your bone in the hypergraph (not the locator)

  • Shift-select the three Translate, Rotate and Scale attribute names (the words), then right click and select Lock Selected (image below)

Rotoscoping

• Use Pan and Scan Tool for Rotoscoping. This is a tool in the XROMM toolshelf, which allows you to Pan, Scan, Rotate, and Drag the camera view while you are rotoscoping.

• Start with a frame at the beginning of the animation sequence, and move the bone (via its animation pivot), with translate and rotate tools so it lines up with the xray bone displayed in the xray camera.

• Making the bone a bright color (e.g. green or pink) and semi-transparent can make rotoscoping easier.

• Once you are satisfied with the alignment of the bone, press S on your keyboard. This sets a Key Frame in the animation, which means Maya marks the characteristics of the bone at that moment. A red line should appear in the animation bar at the bottom of the screen.

• Move forward 5 or 10 frames, and repeat the process again.

• Make sure to always press S before changing frames.

• Maya will interpolate between the Key Frames, filling in your whole animation. Depending on your animation, you may wish to go back and tweak some of the intermediate frames.