4. Rotating Props

Another platforming obstacle common to the genre is objects that rotate, such as a spinning platform you have to constantly move on, or a bar that moves back and forth that you have to jump over.

The second component of an object’s transform is its rotation, and you can manipulate an object to rotate around an axis. There are several different ways you can use rotation to make unique platforming challenges, and you’ll learn how to code them in this section.

Making Props that Rotate

Follow these steps to build code that rotates your props:

1. Create a new Verse class named rotating_prop that inherits from movable_prop using Verse Explorer. Add the <concrete> specifier to this class to expose its properties to UEFN.

   Verse

        # A prop that rotates by an additional rotation or rotates to match
        # a Creative prop's rotation.
        rotating_prop<public> := class<concrete>(movable_prop):

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2. Add the using { /Fortnite.com/Devices/CreativeAnimation } and using { /UnrealEngine.com/Temporary/SpatialMath } statements to the top of the file to import these modules. You’ll need these to animate your prop. The tooltips used in this section are also included here.

   Verse

        using { /Fortnite.com/Devices }
        using { /Fortnite.com/Devices/CreativeAnimation }
        using { /Verse.org/Simulation }
        using { /UnrealEngine.com/Temporary/SpatialMath }
   
        AdditionalRotationTip<localizes>:message = "The rotation to apply to the RootProp."
        ShouldRotateForeverTip<localizes>:message = "Whether the RootProp should rotate forever."
        MatchRotationTargetTip<localizes>:message = "The optional prop whose rotation the RootProp should rotate to. Use this if you do not want to set an Additional Rotation."
   
        # A prop that rotates by an additional rotation or rotates to match
   
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3. At the top of the rotating_prop class definition, add the following fields.

   1. An editable rotation named AdditionalRotation. This is the rotation to apply to the prop. After Move() completes, the prop’s rotation will be offset by this value.

      Verse

                               # The additional rotation to apply to the RootProp.
                               @editable {ToolTip := AdditionalRotationTip}
                               AdditionalRotation:rotation = rotation{}
      

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   2. An editable logic named ShouldRotateForever. This specifies whether the prop should keep rotating without resetting.

      Verse

       # Whether the RootProp should rotate forever.
       @editable {ToolTip := ShouldRotateForeverTip}
       ShouldRotateForever:logic = true
      

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   3. An editable optional creative_prop named MatchRotationTarget. If you want your prop to rotate to match another prop’s rotation, you can set this value rather than using the AdditionalRotation.

      Verse

       # The optional prop whose rotation RootProp should rotate to match. Use this if you
       # do not want to set an additional rotation.
       @editable {ToolTip := MatchRotationTargetTip}
       MatchRotationTarget:?creative_prop = false
      

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   4. A variable rotation named TargetRotation. This is the rotation the prop is currently rotating toward.

      Verse

       # The rotation the prop is currently rotating toward.
       var TargetRotation:rotation = rotation{}
      

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4. Your final class definition should look like this:

   Verse

        using { /Fortnite.com/Devices }
        using { /Fortnite.com/Devices/CreativeAnimation }
        using { /Verse.org/Simulation }
        using { /UnrealEngine.com/Temporary/SpatialMath }
   
        AdditionalRotationTip<localizes>:message = "The rotation to apply to the RootProp."
        ShouldRotateForeverTip<localizes>:message = "Whether the RootProp should rotate forever."
        MatchRotationTargetTip<localizes>:message = "The optional prop whose rotation the RootProp should rotate to. Use this if you do not want to set an Additional Rotation."
   
        # A prop that rotates by an additional rotation or rotates to match
   
   Expand code Copy full snippet(28 lines long)

5. Since you already set up the Move() function that moves your prop in movable_prop, you can override it in this class. Override the Move() function in your rotating_prop class. In Move(), first, check if the MatchRotationTarget is set and save it in a variable RotationToMatch. If so, set the TargetRotation to the RotationToMatch. Otherwise, set it to the AdditionalRotation.

   Verse

        # Rotate the RootProp by applying the TargetRotation, or toward the MoveTarget if one is set.
        Move<override>()<suspends>:void=
   
            # Set the TargetRotation to the MoveTarget's rotation if the MoveTarget is set.
            if:
                RotationToMatch := MatchRotationTarget?.GetTransform().Rotation
            then:
                set TargetRotation = RotationToMatch
            else:
                set TargetRotation = AdditionalRotation

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6. As with translating_prop, specify the animation mode for your animation to play. Initialize a new animation_mode variable named AnimationMode to animation_mode.OneShot. This means your animation will stop once your object reaches its target. If the prop should not rotate forever or not move once and stop, set the animation mode to ping pong. Using ping pong will let you make objects that oscillate back and forth, like the bar on a metronome or a bridge that raises and lowers.

   Verse

        # Set the default animation mode to play.
        # The OneShot animation mode will play the animation once.
        var AnimationMode:animation_mode := animation_mode.OneShot
   
        # If the RootProp should not reset and not stop when it finishes rotating,
        # set the animation mode to PingPong.
        if:
            not ShouldRotateForever? and not MoveOnceAndStop?
        then:
            set AnimationMode = animation_mode.PingPong

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   If you set ShouldReset to false and ShouldRotateForever to true, your prop should keep its position after each animation while continuing to loop Move().

7. Get the rotation for your root prop to rotate toward in a new variable named RotateByMoveRotation by calling RotateBy() on the StartingTransform, passing the TargetRotation.Then call MoveToEase(). Your complete Move() function should look like this.

   Verse

        # Rotate the RootProp by applying the TargetRotation, or toward the MoveTarget if one is set.
        Move<override>()<suspends>:void=
   
            # Set the TargetRotation to the MoveTarget's rotation if the MoveTarget is set.
            if:
                RotationToMatch := MatchRotationTarget?.GetTransform().Rotation
            then:
                set TargetRotation = RotationToMatch
            else:
                set TargetRotation = AdditionalRotation
   
   Expand code Copy full snippet(24 lines long)

8. In your prop_animator device class, add a new editable array of rotating_prop named RotatingProps. Add another for expression to OnBegin() that loops through all the rotating props and calls Setup() on them. Your updated prop_animator class should look like this:

   Verse

        using { /Fortnite.com/Devices }
        using { /Verse.org/Simulation }
        using { /UnrealEngine.com/Temporary/Diagnostics }
   
        TranslatingPropsTip<localizes>:message = "The props that translate (move) using animation."
        RotatingPropsTip<localizes>:message = "The props that rotate using animation."
   
        # Coordinates moving props through animation by calling each prop's Setup() method.
        prop_animator := class(creative_device):
   
   
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9. Save your code and compile it.

Linking Props to Devices

Back in the editor, delete some of the props after the translating props section to create another gap. Add a FG01 Turntable base and a FG01 SpinningBar Double S to your level. Name the base RotatingBase and the bar Spinning Bar. Position the bar above the base, and place both props above the gap.

Setup of the two rotating props. Both the spinning bar and rotating base spin in the same direction at different speeds.

Select your prop animator in the Outliner, and add an array element to RotatingProps for each of your rotating props. Assign each prop with the following values:

Push your changes, then check out your props! Try varying the different values to get different rotations, and try rotating in each of the different dimensions to create different types of obstacles.

Next Up

In the next section, you’ll combine movement and rotation to create props that can do both!

5. Scaling Props

Learn how to manipulate object scales with Verse so they grow and shrink.

Complete Code

Here is the complete code built in this section:

rotating_prop.verse

using { /Fortnite.com/Devices }
using { /Fortnite.com/Devices/CreativeAnimation }
using { /Verse.org/Simulation }
using { /UnrealEngine.com/Temporary/SpatialMath }

AdditionalRotationTip<localizes>:message = "The rotation to apply to the RootProp."
ShouldRotateForeverTip<localizes>:message = "Whether the RootProp should rotate forever."
MatchRotationTargetTip<localizes>:message = "The optional prop whose rotation the RootProp should rotate to. Use this if you do not want to set an Additional Rotation."

# A prop that rotates by an additional rotation or rotates to match

prop_animator.verse

using { /Fortnite.com/Devices }
using { /Verse.org/Simulation }
using { /UnrealEngine.com/Temporary/Diagnostics }

TranslatingPropsTip<localizes>:message = "The props that translate (move) using animation."
RotatingPropsTip<localizes>:message = "The props that rotate using animation."

# Coordinates moving props through animation by calling each prop's Setup() method.
prop_animator := class(creative_device):