Keys and Curves

A Curve (UCurveBase) defines a track of interpolated points to evaluate over a given range. Curves can be vectors, floats, and colors. Each track can have any number of keys that define a time and value. The data can be interpolated between these keys to calculate the value at any point during the Timeline.

Working with Keys and Curves

In this example, you will create a UCurveFloat that defines a curve of interpolated float points to evaluate over a given range.

To create and instantiate a UCurveFloat to a Timeline Component, follow the steps below:

1. Navigate to the Content Browser, click C++ Classes folder, then click Add (+) button and select New C++ Class.

2. Select Actor as a Parent Class.

   Click for full view.

3. Name created Actor as ExampleTimelineComponent.

   Click for full view.

4. When new Actor is created, Visual Studio automatically opens ExampleTimelineComponent.h and ExampleTimelineComponent.cpp files. Navigate to the ExampleTimelineComponent.h file and add the following to the #include section:

   ExampleTimelineComponent.h

       #include "Components/TimelineComponent.h"

5. Next, in the ExampleTimelineComponent class definition, add the following code:

   ExampleTimelineComponent.h

       protected:
   
           UPROPERTY(EditAnywhere, BlueprintReadWrite)
           UTimelineComponent* ExampleTimelineComp;
   
       public:
   
           UPROPERTY(EditAnywhere)
           UCurveFloat* ExampleTimelineCurve;

6. Compile your code.

7. Navigate to the Content Browser, select Add (+) > Miscellaneous > Curve.

8. Select CurveFloat and name it ExampleFloatTrack.

9. In Content Browser navigate to the folder with your ExampleTimelineComponent class, right click it and select Create Blueprint Class based on ExampleTimelineComponent. Name it BP_ExampleTimelineComponent.

10. Open the BP_ExampleTimelineComponent class defaults, navigate to the Detail panel and assign your Example Timeline Curve with your ExampleFloatTrack.

11. Double-click your Example Float Track from the Content Browser to open the Timeline Editor.

Adding Keys

Keys are added by pressing the Enter key, or by right clicking on the gray bar and selecting the action Add Key from the context menu.

Editing Keys

The time and value of the key can be set by clicking the key and entering the values into the time and value fields near the top of the track.

Deleting Keys

Selected keys can be deleted by pressing the Delete key on the keyboard, or by right clicking on the key you want to delete and selecting the action Delete from the context menu.

Moving Keys

To move a key along the timeline, select the key, then drag it. Multiple keys can be selected using the Ctrl key. Dragging horizontally will update the Time value of the key, while dragging vertically will update the Value.

Key Interpolation

By right-clicking a key, a context menu menu appears to choose the interpolation type for selected key.

Key interpolation only affects the curve between the key you interpolate for and the next key after that. For example, with all other keys set to Linear, and the center key set to Cubic-Auto, the track will look similar to the image below.

Available interpolation types are:

• Auto

• User

• Break

• Linear

• Constant