How do I change an animation curve to linear in Unity?

To change an animation curve to linear in Unity, you need to select the animation keys and adjust their tangents. A linear tangent creates a straight line between two keys, resulting in a constant rate of change.

Steps to Make Animation Curves Linear in Unity

Making your animation curves linear ensures a smooth, constant transition between keyframes, avoiding acceleration or deceleration. Follow these steps within Unity's Animation window:

1. Open the Animation Window: Select the GameObject with the animation you want to edit. Open the Animation window (Window > Animation > Animation).
2. Select the Property: In the Animation window, select the specific property (e.g., Position.x, Rotation.y) whose curve you want to modify. This will display the animation curve in the graph view.
3. Select All Keys: To apply the linear tangent to the entire curve, Push Ctrl+A to select all curves and keys. This highlights all keyframes on the displayed curve(s).
4. Access Tangent Options: With the keys selected, Right-Click on any one of the keys. A context menu will appear with various options for the selected key(s).
5. Choose Tangent Type: From the context menu, navigate to the tangent options. Click “Both Tangents”. This option allows you to set the tangent type for both the incoming and outgoing sides of the selected key(s) simultaneously.
6. Apply Linear Tangent: In the submenu that appears after clicking "Both Tangents", Click “Linear”.

Once you click "Linear", the tangent handles for all selected keys will adjust, and the curve segments between them will become straight lines, representing a linear transition.

Understanding Tangents in Unity Animations

In Unity's Animation window, keys represent specific values at certain points in time. The curve between these keys determines how the value changes over time. Tangents control the shape of this curve as it enters and exits a keyframe.

• Linear Tangents: Create a constant speed of change between keys. The graph segment is a straight line. This is useful for uniform motion or transitions.
• Free Tangents: Allow manual manipulation of tangent handles for complete control over curve shape.
• Broken Tangents: Allow independent control over the incoming and outgoing tangents of a single key.
• Auto Tangents: Unity attempts to automatically smooth the curve.
• Clamped Tangents: Similar to Auto, but prevents overshoots.

By selecting "Both Tangents" and then "Linear", you enforce a linear interpolation across the entire selected portion of the curve using the steps outlined in the reference: Push Ctrl+A to select all curves and keys. Right-Click on any one of the keys. Click “Both Tangents”. Click “Linear”.

This process is essential for animators who need precise control over timing and value changes, ensuring predictability and consistency in their animations.