SmoothMotion

Smooth Motion belongs to Fusion's Optical Flow toolset and is designed for temporal smoothing of channel data carried inside an image stream. A classic use is reducing high-frequency temporal jitter in Disparity, but the node can also smooth Color, Z, normals, vectors and other AOV groups.

Smooth Motion does not generate motion vectors. Its input stream must already contain both Vector and Back Vector data, normally from an upstream Optical Flow node or from an EXR sequence that stores the vectors.

Blackmagic explicitly states that missing Vector/Back Vector data causes Smooth Motion to print error messages in the Console. MediaIn directly into Smooth Motion is therefore not a valid baseline graph unless that stream already carries vectors.

The node has one physical orange image input. Color, vectors and AOV data travel inside that same image/multilayer stream; there is no separate green Vector input and no second Layer Data socket.

This matters when reading a Flow: MediaIn → OpticalFlow → SmoothMotion is a serial chain of image nodes. Motion vectors are data in the stream, not separate cables between nodes.

The Channels section exposes Color, Background Color, Z, Texture, Coverage, Normal, Vector, Back Vector, World Position and Disparity. These checkboxes select the channel groups that Smooth Motion will temporally smooth.

Vector and Back Vector checkboxes do not enable the required guidance data. The vectors must exist at the input regardless; checking those boxes means the vector fields themselves become smoothing targets.

A missing selected target channel behaves differently from missing motion vectors: Blackmagic notes that Smooth Motion does not fail and does not print an error just because a checked smoothing channel is absent.

That distinction makes channel inspection essential. First verify Vector and Back Vector, then verify the target AOV, and only then judge whether Smooth Motion changes the intended data.

One Smooth Motion node examines the previous, current and next frame for a total neighborhood of three frames. Two nodes in sequence examine five frames; three nodes examine seven.

Unlike Smear, Smooth Motion has no user-facing Frames Either Side control. Effective temporal reach grows through cascading nodes, while sample alignment is driven by optical-flow vectors.

Smooth Motion can also smooth Vector and Back Vector themselves. Blackmagic warns that this can make interpolation worse when a shot contains conflicting motions, erratic movement, jitter or rapid bouncing.

A documented two-stage technique is to use the first Smooth Motion node to smooth Vector and Back Vector, then use a second Smooth Motion node to smooth a target such as Disparity with the already-smoothed motion field.

That two-stage method is not automatically superior. Occlusions, crossing objects and abrupt direction changes can make smoothed vectors less accurate, so the vector-smoothing stage should survive only if an A/B comparison proves it helps.

Color can be selected as a temporal-smoothing target, but Smooth Motion is not a general stabilizer, retiming tool or motion-blur effect. It smooths channel values across motion-aligned neighboring frames.

Disparity is one of Smooth Motion's original and most useful applications. Small frame-to-frame instability in stereo disparity can create edge/fringing artifacts; temporal smoothing can make that channel more coherent.

Z can be smoothed when a depth pass contains temporal noise or jitter. Depth discontinuities still need close review because excessive smoothing can bleed depth behavior between separate surfaces.

Normal and World Position are CG/AOV use cases. Their smoothing is useful only when the passes are valid and registered to the beauty image; Smooth Motion cannot repair fundamentally misaligned render passes.

Coverage and Texture are additional channel groups. Do not enable them speculatively: confirm the stream actually contains those data and that a downstream process benefits from their temporal smoothing.

Background Color is a channel group, not a second Background connector. Smooth Motion still has only one image input.

Resolve 21 updated the motion-vector pipeline so Optical Flow can output Vector and Back Vector as discrete layers compatible with Fusion's multilayer system. Smooth Motion is one of the tools that can consume those layers.

The captured Controls panel includes Use Layers for Input Vectors. Treat this as a data-layout choice that must match how the upstream vectors are stored, rather than as a quality or strength mode.

Do not copy the Layers state blindly. Inspect whether your upstream source carries vectors as Resolve 21 layers or as legacy auxiliary channels, then match the input-vector mode and verify the Console is clean.

The captured screenshot shows all channel boxes and Use Layers unchecked. That is evidence of one saved UI state, not a claim about factory defaults or a recommended preset.

Smooth Motion outputs an image/multilayer stream. Unselected channels pass without the chosen smoothing operation while selected channels may be modified and remain available to downstream tools.

Judge Smooth Motion over time. A still frame can reveal a local edge artifact, but it cannot tell you whether temporal jitter improved or whether rubbery/lagging behavior was introduced.

A production check should cover channel inspection, Console status, bypass/active playback, frame stepping at occlusions/fast motion, and the actual downstream use of the AOV rather than only the beauty image.

If the real task is retiming, motion blur or frame reconstruction, switch to TimeSpeed/TimeStretcher/SpeedWarp, Vector Motion Blur or Repair Frame instead of forcing Smooth Motion into a different role.