Endpoints & variationsEndpoints & variations

Endpoints say where a tween goes. Variations derive a stronger, slower, or later version from a definition’s own values each time it starts. Anatomy and variations introduce both.

Endpoints

TValue is the property’s value type, such as Vector2 for a position.

Member	Type	Default	Meaning
From	TValue?	null	Start value; null uses the property’s value at start
To	TValue?	null	End value; null uses the property’s value at start
By	TValue?	null	Offset to add instead of a To, on top of other changes to the property while it plays

Endpoint forms

Built-in constructors and shorthand methods also accept these forms. Components are double, so they need no f suffix:

Endpoint	Also accepts	Example
float	Any number	new Tweens.ModulateAlpha(0.5, 0.2)
Vector2, Vector3, Vector4	A tuple, or a collection of components	(400, 180), [400, 180]
Vector2, Vector3 scales	One number for every axis	new Tweens.Scale2D(1.2, 0.2)
Color	Three or four components, an HTML code, or a color name	(1, 0.5, 0), [1, 0.5, 0, 0.8], "#ff8800", "tomato"

• Three color components leave the alpha at 1.
• The compiler checks a tuple’s component count, and that each component converts to double.
• When the tween is created, a collection with the wrong number of components throws an ArgumentException, and an unknown color name an ArgumentOutOfRangeException.

Relative offsets

• Set To or By, not both. A To tween on the same property still sets it outright.
• With From, the tween runs from From to From plus By, like a To tween.
• Each repeat adds By again, so Repeats = 2 moves three times as far. A ping-pong cycle comes back to where it started.
• A Fill that doesn’t retain the final value takes the offset back out at the end, and keeps other changes.
• A quaternion offset rotates about the node’s own axes, so the tween ends at start * By.

Variations

When a tween starts, each of these values becomes factor × value + delta:

Member	Type	Default	Meaning
FactorFrom, FactorTo, FactorBy	double	1	Multiply From, To, or By
DeltaFrom, DeltaTo, DeltaBy	TValue?	null	Then add this; null adds nothing
FactorDuration	double	1	Multiply Duration
DeltaDuration	Duration	0	Then add these seconds
FactorDelay	double	1	Multiply Delay
DeltaDelay	Duration	0	Then add these seconds, as in a per-start stagger

With To left out, FactorTo scales the value captured at the start.

Rules

• Factors and deltas apply once, when the tween starts. A non-retaining Fill restores the captured value, not an adjusted one.
• For a quaternion, the factor scales the rotation angle and the delta rotates about the node’s own axes.
• FactorBy and DeltaBy need a By. FactorTo and DeltaTo don’t apply to a By tween. Both combinations are rejected.
• Adjusting From fixes the start of a By tween, as an explicit From does.
• The adjusted duration and delay must not be negative, and Offset must fit within the adjusted duration.
• Factors, DeltaDuration, and DeltaDelay must be finite. Invalid values reject the start.

Callback endpoints

Callback value definitions such as Tweens.Float animate no property; OnUpdate receives each value. With no From or To, they use zero, transparent black, or identity for that endpoint, and add By to their start value. The catalog lists them.

When tweens compete

Two tweens may animate the same property. Each update, the one started last wins. Axis and alpha definitions, such as Tweens.Position2DX and Tweens.ModulateAlpha, read the other components on every write, so an X tween and a Y tween combine.