DirectionalBlur

DirectionalBlur [DrBl] is a 2D processor for directional motion streaks, light trails and fast transitions. It receives an ordinary image and outputs 2D RGBA. No 3D scene, optical flow or motion-vector pass is needed.

The Controls tab has six main settings: Type, Center, Length, Angle, Glow and Clipping Mode. Two genuine Inspector screenshots illustrate the controls and Type menu. The separate blue Effect Mask input limits the effect; it is not a direction input.

Type offers four modes: Linear, Radial, Centered and Zoom. They are not just four cosmetic presets of the same straight blur; each distributes the sampled image differently.

Linear stretches the image along a straight direction. It is useful for background speed streaks and camera-motion styling. Angle defines the orientation, and the sign of Length can reverse the heading.

Centered also uses a straight path but distributes blur on both sides of the original position. Use it when a title or graphic should have a more symmetric smear rather than a trailing streak.

Radial creates blur relative to a chosen Center. Place Center on the subject or visual focal point before increasing Length. A non-zero Angle can make the result look like a rotating vortex.

Zoom changes the scale of the smear relative to Center to imitate camera-zoom streaking during a slow exposure. It shares the Center control with Radial but produces a different pattern.

The critical naming trap is that Center X/Y works only in Radial and Zoom. Despite its name, Centered does not use the Center coordinate. In both straight modes, Angle controls the direction.

Length sets strength and heading. At 0 the blur path has no extent, making it a useful reference and a clean endpoint for animated transitions. Negative Length reverses the heading relative to Angle; it is not simply a weaker amount.

Angle changes meaning with Type. In Linear and Centered it points the straight streak; in Radial and Zoom it adds a rotational component. With non-zero Length, Angle can turn a clean radial or zoom shape into a spin/whirlpool.

For that reason, begin a Radial or Zoom test with Angle=0. Set Center and Length first, then deliberately introduce spin if the design calls for it.

Glow increases the brightness of the established streak and can suggest extra light exposure during a longer shutter interval. It does not correct Type or Angle. Set Glow=0 while diagnosing geometry and add it afterward.

DirectionalBlur processes all four RGBA channels. On Text+, PNG and keyed elements it also changes alpha coverage. Inspect the alpha channel in the Viewer and judge the composited edge against a contrasting background.

Strong blur of transparent graphics may reveal unwanted colored fringes. These can come from source RGB hidden under alpha or premultiplication behavior; more Glow or a different Type is not necessarily the remedy.

Effect Mask connects to the separate blue input and mixes the already-computed result locally. Rectangle or Polygon can gate the streak, but their shapes do not become blur paths and cannot replace Center or Angle.

Placement in the graph matters. Blur a background branch before Merge and a Text+ foreground can remain sharp. Put DirectionalBlur after Merge and the already-assembled composite is blurred instead.

Clipping Mode governs image boundaries and the Domain of Definition (DoD). Its choices — Frame, Domain and None — are technical boundary policies, not blur-quality options or a substitute for Crop.

Frame expands processing to the full frame and treats regions outside the incoming DoD as black/transparent. Domain respects the incoming DoD and can clip large streaks. None performs no source clipping; unavailable samples are treated as black/transparent.

A limited-DoD Text+ or PNG element with a substantial Length is more useful for comparing Clipping Mode than full-frame footage, where switching modes may have little visible effect.

For a transition, establish clean endpoints at Length=0 and animate a burst between them. Change one control at a time: Length first, then Angle, Center or Glow if required. Judge motion in playback rather than only on stills.

DirectionalBlur cannot infer different speeds and directions for separate objects. For blur driven by actual per-pixel motion, evaluate Vector Motion Blur or an optical-flow workflow instead of trying to approximate it with a single global node and many masks.

Quality control: compare Linear and Centered on a thin line, compare Radial and Zoom at Angle=0, inspect alpha and image edges at 100%, and check placement relative to Merge. Play the entire animation to catch jumps or unexpected bursts.

The article includes two original Inspector captures, showing Controls and the open Type menu. They document visible labels and layout, but do not establish performance or extreme-value behavior for every Resolve release.

For automated and portable setups, confirm serialized Type and Clipping Mode values through a .setting/.comp export from the target Resolve build. A static reference describes the intent; live Fusion is required to certify exact compatibility.