tweening

Tweening in FlatRedBall2

Built on the FlatRedBall.InterpolationCore NuGet. FRB2 ships two extension methods that return a running Tweener:

using FlatRedBall2.Tweening;              // Entity.Tween / Screen.Tween
using FlatRedBall.Glue.StateInterpolation; // InterpolationType, Easing, Tweener

// Entity-scoped (primary) — tween dies with the entity. Target a child shape directly:
var t = this.Tween(v => _circle.Radius = v, from: 0f, to: 100f, duration: TimeSpan.FromSeconds(0.5),
                   InterpolationType.Cubic, Easing.Out);

// Screen-scoped (for tweens with no natural entity owner).
this.Tween(v => Camera.Zoom = v, Camera.Zoom, 1.5f, TimeSpan.FromSeconds(0.3));

Two using directives — why

InterpolationType, Easing, and Tweener come from the upstream FlatRedBall.Glue.StateInterpolation namespace and are not re-exported under FlatRedBall2.Tweening. Gum already depends transitively on FlatRedBall.InterpolationCore (via FlatRedBall.GumCommon), so the upstream namespace is present in every FRB2 project whether you use tweens or not. Declaring FRB2 wrappers with the same names would create IntelliSense auto-import ambiguity — picking the wrong one silently compiles but produces the wrong types. One set of types everywhere beats two similar ones, even if the upstream namespace is ugly.

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Choosing the scope

Use Entity.Tween whenever the setter writes to an entity or its children. Destroying the entity clears its tweens automatically, so there is no use-after-destroy risk when the entity dies mid-tween.

Use Screen.Tween only when there is no entity owner — screen fades, global UI transitions, camera-level state.

If in doubt, pick Entity.

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Pause behavior

Tweens freeze while Screen.IsPaused is true, alongside the rest of the Activity pipeline. For finer-grained control, override ShouldAdvanceTweens on the Entity or Screen subclass — e.g., freeze tweens on a single stunned entity without pausing the whole screen.