Understanding Constant Interpolation in Blender

Constant interpolation in Blender is a keyframe transition mode that causes an object or property to instantly jump from one value to the next without any smooth motion in between. Unlike standard interpolation types that calculate gradual changes over time, constant interpolation holds the exact value of a keyframe until the playhead hits the very next keyframe. This results in abrupt, stepped transitions, making it an essential tool for blocking out character animations, creating stop-motion effects, and toggling binary settings like object visibility.

How Constant Interpolation Works

In animation software, interpolation refers to how the system calculates intermediate values (the "in-betweens") between user-defined keyframes.

  • Bezier Interpolation creates smooth curves with gradual acceleration and deceleration.
  • Linear Interpolation creates straight-line transitions at a steady, fixed speed.
  • Constant Interpolation completely eliminates intermediate calculations.

When constant interpolation is applied, the property value remains entirely static following Keyframe A until the timeline reaches Keyframe B. The exact instant the playhead lands on Keyframe B, the property snaps immediately to the new value.

Primary Use Cases in Blender

1. Blocking Out Animations (Pose-to-Pose)

Animators frequently use constant interpolation during the initial "blocking" phase of an animation. By switching keyframes to constant, animators can focus purely on key poses and timing without being distracted by Blender's automatic, smooth transitions. This prevents the software from adding unwanted movement before the main poses are finalized.

2. Stop-Motion and Stylized Animation

For projects requiring a low frame rate or hand-drawn aesthetic (such as 2D-style 3D animation or stop-motion LEGO styles), constant interpolation keeps poses rigid across specific frame counts. This allows creators to hold poses for two or three frames at a time ("animating on twos" or "threes") to mimic classic frame-by-frame techniques.

3. Hard Camera Cuts

When animating cameras, constant interpolation allows you to switch camera positions or angles instantly on a single frame, simulating traditional cinematic scene cuts within a single shot.

4. Toggling Discrete and Binary Properties

Certain properties in Blender do not have meaningful mid-points. Examples include:

  • Object hide/show visibility in the viewport or render.
  • Modifier switches (turning a modifier on or off).
  • Stepped texture indices or material swaps.

Using constant interpolation ensures these settings trigger precisely on the target frame without unexpected behavior on surrounding frames.

How to Apply Constant Interpolation

  1. Open the Dope Sheet, Timeline, or Graph Editor in Blender.
  2. Select the keyframe(s) you wish to modify.
  3. Press T on your keyboard to open the Set Interpolation Mode menu.
  4. Select Constant from the list (or press 1 on the main keyboard).

Alternatively, you can change your default interpolation mode for all newly created keyframes by going to Edit > Preferences > Animation > Default Interpolation and setting it to Constant.