Timelines

Timelines in Unreal Engine are a versatile tool used to create smooth, time-based animations or transitions for objects and properties. They allow you to define custom curves and events that can modify variables like position, rotation, scale, or material properties over time. This makes them perfect for tasks such as opening doors, moving platforms, or changing light intensity.

How to Use a Timeline

1. Add a Timeline Node: Open your Blueprint (Level Blueprint or Actor Blueprint). In the Event Graph, right-click and search for Add Timeline. This creates a new Timeline node. Double-click it to open the Timeline Editor.
2. Create Tracks: Inside the Timeline Editor, you can add different types of tracks depending on what you want to animate:
   • Float Track: Animates a single value, like the intensity of a light or the movement along one axis.
   • Vector Track: Animates three values, such as position (X, Y, Z) or color (R, G, B).
   • Event Track: Triggers specific events at chosen times.
   • Color Track: Changes color properties over time.
   Click the + Add Track button to choose the type of track you need.
3. Define Keyframes: Add keyframes to specify how the value changes over time:
   • Right-click in the graph area to add a keyframe.
   • Set the time and value for each keyframe.
   • Adjust the curve between keyframes to create smooth transitions.
4. Customize the Timeline: In the Timeline Editor’s Details panel, you can set the total duration and looping behavior of the Timeline:
   • Length: Defines how long the animation lasts.
   • Loop: If enabled, the Timeline will repeat continuously.
5. Use Timeline Output: In the Event Graph, the Timeline node provides execution pins and outputs for each track you create. Connect the outputs to nodes that control your desired properties.

Example: Moving a Door

1. Add a Timeline: Create a Timeline node named “DoorMovement” in your Blueprint.
2. Add a Float Track: Open the Timeline Editor and add a Float Track. Add keyframes at:
   • Time = 0, Value = 0 (door closed).
   • Time = 2, Value = 1 (door fully open).
   This will smoothly animate a value from 0 to 1 over 2 seconds.
3. Modify the Door’s Position: Back in the Event Graph, connect the Timeline’s update pin to a Set Relative Location node. Use the float output from the Timeline to interpolate the door’s position between its closed and open states using a Lerp (Vector) node.
4. Trigger the Timeline: Add an event, such as a key press or a trigger box overlap, to start the Timeline. Connect the event to the Play input pin of the Timeline node.

Example: Changing Light Intensity

1. Add a Timeline: Create a Timeline node named “LightFade” in your Blueprint.
2. Add a Float Track: Add keyframes for light intensity:
   • Time = 0, Value = 3000 (low brightness).
   • Time = 5, Value = 10000 (high brightness).
3. Modify the Light’s Intensity: Connect the float output to the Set Intensity node of the light.
4. Start the Timeline: Trigger the Timeline using an event, such as when the player enters a specific area.

Tips for Using Timelines

• Reversing the Timeline: Use the Reverse input pin to play the Timeline backward, which is useful for closing doors or fading out effects.
• Pausing and Resuming: Use the Pause and Play from Start pins for more control over the animation.
• Triggering Events: Use Event Tracks to trigger specific actions, like playing a sound or spawning objects, at certain points during the Timeline.

Timelines provide precise control over time-based changes, making them essential for creating smooth and engaging animations in your Unreal Engine projects.