Runway

Runway Motion Brush Not Working — How to Fix It

Runway's Motion Brush tool allows you to paint motion onto specific regions of an image before generating video, but many users find that their selected areas show no movement in the final output. This issue typically affects creators using Gen-2 who have overlapping brush zones, low-contrast selections, or too many motion areas defined. If your Motion Brush strokes seem to be ignored during generation, the steps below will help you resolve it quickly.

Why does this error happen?

The Motion Brush feature relies on Runway's Gen-2 model to interpret spatially distinct, high-contrast painted regions and map directional motion vectors to each one. When brush areas overlap, use low opacity, or exceed the model's recommended limit of five zones, the generation pipeline struggles to disambiguate which pixels belong to which motion instruction. Additionally, using Motion Brush on an unsupported model version — such as Gen-1 — will silently discard all brush data, causing the output video to appear static. The model also requires clear edge boundaries between brushed and unbrushed regions to correctly isolate and animate the intended subject.

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How to fix it

Use a High-Contrast Brush for Clear Selection

When painting your motion zones, use the brush at full opacity and ensure the painted area clearly covers your intended subject without bleeding into the background. High-contrast, well-defined brush strokes give the Gen-2 model the clearest signal about which region should receive motion. Avoid semi-transparent or feathered edges, as these can cause the model to ignore or misinterpret the selection.

Confirm You Are Using Gen-2 with Motion Brush Support

Motion Brush is exclusively supported on Runway's Gen-2 model, so verify that Gen-2 is selected in your generation settings before painting any brush strokes. If you are on Gen-1 or another model variant, the Motion Brush panel may appear available but will have no effect on the output. Switch to Gen-2 in the model selector, then reapply your brush strokes before regenerating.

Limit Motion Brushes to 5 or Fewer Areas

Runway's Motion Brush system is optimized to handle up to five distinct motion zones per image. Defining more than five areas can cause the model to drop or merge motion instructions unpredictably, resulting in static or incorrectly animated regions. Clear all existing brush layers and repaint only the most essential motion zones, keeping the total count at five or below.

Try a Different Motion Direction

Some motion directions may conflict with the natural geometry of the subject in your image, causing the model to suppress the movement to avoid unrealistic output. If a particular directional arrow produces no visible motion, reset the brush for that zone and experiment with an adjacent or opposite direction. Horizontal and subtle diagonal motions tend to produce the most consistent results across varied image types.

Pro tip

Before generating, zoom into your Motion Brush canvas and confirm that each painted zone is fully opaque, non-overlapping, and covers the subject cleanly — taking 30 seconds to audit your brush layers before hitting Generate can save multiple failed generation credits.

Frequently asked questions

Why does my Motion Brush selection disappear after I switch settings?

Changing the model version or certain advanced settings can reset the Motion Brush canvas in Runway's interface. Always apply your brush strokes as the final step before clicking Generate to ensure your selections are preserved.

Can I use Motion Brush on uploaded videos or only on images?

Motion Brush in Runway Gen-2 is designed for use with static images as the generation starting point, not uploaded video clips. If you are working with a video input, you will need to extract a key frame as an image and use that as your base for Motion Brush generation.

Does Motion Brush work on the free Runway plan?

Motion Brush is available on the free tier but generation credits are limited, which can make troubleshooting costly. Upgrading to a paid plan gives you more credits to iterate and refine your Motion Brush settings without running out mid-session.

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