Workflows

Workflows

Geo Mask

Draw a mask once and let it follow the shot, stuck to tracked 3D geometry.

Rotoscoping by hand means moving the same points on frame after frame. Geo Mask does that part for you. You draw the shape once, tell it which geometry the shape is sitting on, and it sticks there for the rest of the shot.

It works by casting each mask point onto your 3D geometry, then projecting those points back through the solved camera on every frame. The shape moves because the geometry and camera move.

You'll find it in the Movie Clip Editor sidebar under the Dope Track tab.

Before You Start

  • A solved camera in the scene, from Auto Track into Output 3D
  • A mesh that lines up with whatever you're masking. It doesn't need to be detailed. A plane or a rough box is usually enough.
  • A mask with at least one layer, created in the Clip Editor's Mask mode

Sticking A Shape To Geometry

  1. Find a frame where the thing you're masking is clearly visible. This becomes your reference frame.
  2. Draw your mask shape on that frame, as you normally would.
  3. Open the Geo Mask panel and pick your Camera and Geometry.
  4. Press Link Shape to Geometry.

That's it. Scrub through the shot and the shape follows.

What happened under the hood: every point and handle got cast onto the mesh, and their projected positions were baked across the whole shot as mask shape keys.

Fixing Frames That Drift

Geometry is never a perfect match for what's in the plate, so some frames will need a nudge.

  1. Go to the frame that's off.
  2. Move the points where they should be.
  3. Press Set Keyframe.

Your correction gets keyed on that frame and eases off toward the neighboring keyframes, so you don't get a sudden jump. The reference frame stays at zero correction, and past the outermost keyframes the correction holds steady. The baked 3D motion keeps running underneath all of it.

Fix the worst frame first, then check whether the frames around it still need work. They often don't.

Working With Layers

Every button acts on the active mask layer, which is the one highlighted in the list. Layers stay completely independent, so you can link one to a wall and another to a door, each with its own geometry.

Add, remove and rename layers using the buttons beside the list.

Starting Over

Unlink Shape removes the baked keys and every correction for the active layer, and puts the points back where you originally drew them.

To relink a shape, unlink it first. That way you're always recasting from a shape you can actually see, rather than from something baked.

Seeing Your Keyframes

Turn on Keys in Timeline to mark your correction keyframes in the timeline, and pick whatever color reads best against your footage.

When It Doesn't Work

"No active mask." Switch the Clip Editor to Mask mode and create or pick a mask first.

"Choose the solved Camera." The panel needs a camera. Leave the picker empty and it falls back to the scene camera, but there has to be one somewhere.

"Must be a mesh." Curves and surfaces won't work. Convert to a mesh first.

The shape sits in the wrong place after linking. Your geometry probably isn't lined up with the plate. Check it against the reference frame in the viewport, then unlink, fix the geometry, and link again.

The shape drifts everywhere. Usually a weak camera solve rather than a Geo Mask problem. Check the solve first.