Gradients

Multi-stop gradient types for sampling color, float, and vector values over a normalized range — used by motion tracks and feedback effects.

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The Gradients utility provides three parallel gradient types for interpolating values over a normalized [0,1] range using a sorted list of marker points. All types are fully reflected (SerializeContext + EditContext) and editable in the Inspector with visual marker placement. Gradients are lazily sorted before evaluation.

Used by: FeedbackMaterialTrack (color/float animation), UiImageColorTrack, procedural visual effects, any system needing editable color or value ramps.

For usage guides and setup examples, see The Basics: GS_Core.

Gradient Slider in the O3DE Inspector

Gradient Types
Marker Structs
Gradient Classes
ColorGradient Channels
Usage Example
See Also

Gradient Types

Type	Value Type	Description
`FloatGradient`	`float`	Single float value ramp
`Vector2Gradient`	`AZ::Vector2`	2D vector ramp
`ColorGradient`	`AZ::Color`	RGBA color ramp with separate color and alpha channels

Marker Structs

Each gradient type has a corresponding marker struct that defines a single stop on the gradient.

FloatGradientMarker

Field	Type	Description
`markerValue`	`float`	The float value at this stop
`markerPosition`	`float`	Position in [0, 1] along the gradient

Vector2GradientMarker

Field	Type	Description
`markerValue`	`AZ::Vector2`	The 2D vector value at this stop
`markerPosition`	`float`	Position in [0, 1] along the gradient

ColorGradientMarker

Field	Type	Description
`markerColor`	`AZ::Color`	The color (RGB + A) at this stop
`markerPosition`	`float`	Position in [0, 1] along the gradient

Gradient Classes

All three gradient types share the same structure and interface:

Field / Method	Description
`slider`	`AZStd::vector<Marker>` — the sorted list of gradient stops (field name for Float/Vector2)
`sorted`	Internal dirty flag; gradient is lazily sorted before `Evaluate` is called
`SortGradient()`	Sorts markers by position. Called automatically before evaluation when markers change.
`Evaluate(float t)`	Returns the interpolated value at normalized position `t` in [0, 1]

ColorGradient

ColorGradient maintains two separate marker lists for independent RGB and alpha control:

Field	Description
`colorSlider`	`AZStd::vector<ColorGradientMarker>` — RGB stops
`alphaSlider`	`AZStd::vector<ColorGradientMarker>` — alpha stops

ColorGradient Channels

ColorGradient exposes three evaluate methods for flexible sampling:

Method	Returns	Description
`Evaluate(float t)`	`AZ::Color`	Full RGBA color — samples both `colorSlider` and `alphaSlider`
`EvaluateColor(float t)`	`AZ::Color`	RGB only — alpha is always 1.0
`EvaluateAlpha(float t)`	`float`	Alpha channel only

Usage Example

#include <GS_Core/Utility/Gradients/FloatGradientUtility.h>
#include <GS_Core/Utility/Gradients/ColorGradientUtility.h>

// Sample a float gradient at normalized progress (0 → 1)
float value = myFloatGradient.Evaluate(normalizedProgress);

// Sample full RGBA color
AZ::Color color = myColorGradient.Evaluate(normalizedProgress);

// Sample RGB and alpha independently
AZ::Color rgb   = myColorGradient.EvaluateColor(normalizedProgress);
float alpha     = myColorGradient.EvaluateAlpha(normalizedProgress);

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