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ILogicFloatDriver

Interface

Inheritance 1 ancestor · 20 siblings · 117 descendants

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A logic driver that produces a number. A logic driver is a small object that computes a value on request. Drivers nest: most take other drivers as operands, so data builds an expression out of them, such as "the health of this unit, mapped to 0..1, passed through a curve". The client uses the result to drive a material parameter, an effect, an animation or a piece of UI.

The source. A driver is always evaluated for one object, the source, and it passes the same source on to its operands. Which object that is depends on what holds the expression:

Holder Source
A dynamic material parameter (DynamicMaterialParameterDef.driver) The object the material is drawn for: a unit, a map prop, a map mesh
A persistent effect (its conditions and its play speed) The unit that carries the effect
An animation graph (StateAnimClipData.SpeedRatioDriver, the logic driver updaters) The object that owns the graph
A particle effect (VfxFloatLogicDriver) The object the effect is bound to
A map light updater The game entity of the light, for a light that is an entity component
A LogicDriverViewController The local player's champion
A map visibility controller (TransitionTimeDriver) None

A driver that reads a unit checks what the source is. When there is no source, or it is the wrong kind of object, the driver returns a fixed fallback, which is 0 for most drivers. Drivers that read no object, such as a constant or the time, work with any source and with none.

Evaluation. Nothing caches a result. Every read walks the whole expression again, and a dynamic material parameter is read every frame for every object that shows the material. Most drivers keep no state. The few that do, such as LerpMaterialDriver, move their state forward each time they are evaluated, not once per frame.

Value kinds. There are drivers for a four-component vector (ILogicDriver), a float, an int and a bool. Each narrower kind also counts as the wider ones:

  • a bool driver read as an int gives 1 or 0,
  • an int driver read as a float gives the same number,
  • a float driver read as a vector gives the float in all four components.

So a property that takes a float driver also takes an int or bool driver, and a float driver can fill a property that takes an ILogicDriver, which is how most material parameters use one.

Referenced by 28 classes · 33 properties

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