How to Blend Animation Strips in Blender NLA Editor

This guide covers how to create smooth transitions between animation strips using the Non-Linear Animation (NLA) editor in Blender. You will learn the setup required to convert actions into editable NLA strips, how to overlap strips across tracks, and how to configure blending properties such as Blend In, Blend Out, and blend modes for seamless transitions.

1. Convert Actions to NLA Strips

Before blending, your keyframed animations must be converted into NLA strips:

  1. Open the Dope Sheet and switch the mode to Action Editor.
  2. Select the Action you want to use.
  3. Click the Push Down button to send the action to the NLA Editor as an active strip.
  4. Repeat this process for the second animation you want to blend.

2. Arrange Strips in the NLA Editor

  1. Switch your workspace or editor window to the Non-Linear Animation editor.
  2. Ensure both strips are placed on separate tracks, one stacked above the other.
  3. Drag the second strip horizontally along the timeline so that its beginning overlaps with the end of the first strip. The length of this overlap represents the duration of your transition.

3. Configure Blend In and Blend Out Values

  1. Select the top (or incoming) animation strip.
  2. Press N to open the properties sidebar on the right side of the NLA Editor.
  3. Go to the Strip tab and expand the Active Strip drop-down menu.
  4. Locate the Blend In and Blend Out fields:
    • Blend In: Set this value (in frames) to match the number of overlapping frames. This creates a smooth fade-in from the underlying strip.
    • Blend Out: Use this setting if the strip transitions into another strip further down the timeline.
  5. In the same panel, set the Blending mode to Replace for standard sequential transitions, or Add / Combine if you are layering secondary motion (such as breathing or gestures) on top of a base animation.

4. Use Automatic Blending (Alternative Method)

Blender can also calculate transitions automatically:

  1. Select the strip you want to blend.
  2. In the N panel under the Strip tab, check the box labeled Auto Blend In/Out.
  3. Blender will automatically adjust the blend duration based on the overlap between adjacent strips.