AgX

AgX is a tone mapper designed by Troy Sobotka and implemented for real-time use by Benjamin Wrensch (Missing Deadlines). It approaches tone mapping from a rigorous color-science perspective, producing results that feel natural and photographic — especially in high-contrast scenes where other operators tend to clip or hue-shift highlights.

How it works

AgX processes scene-referred linear HDR through a pipeline modeled on photographic film response:

1. Input matrix — rotates from scene-linear into a working color space that de-correlates the channels.
2. log₂ compression — maps the wide HDR range to a workable log domain, clamped to [-12.47, 4.03] EV.
3. Normalization — maps the log range to [0, 1].
4. Sigmoid curve — a 6th-order polynomial approximation that smoothly rolls off both shadows and highlights.
5. ASC-CDL look — applies the selected look via slope/power/saturation.
6. Inverse input matrix — rotates back to display space.
7. EOTF — pow(x, 2.2) to convert to display-referred.

Look presets

The AgX Look setting selects one of three creative intents:

Default

A neutral, reference look. No color grading applied — closest to a straight film scan.

Parameter	Value
Slope	(1.0, 1.0, 1.0)
Power	1.0
Saturation	1.0

Golden

Warm, autumnal tones. Reduced blue channel and slightly soft contrast — reminiscent of golden-hour photography.

Parameter	Value
Slope	(1.0, 0.9, 0.5)
Power	0.8
Saturation	0.8

Punchy

High-impact look with boosted contrast and saturation. Good for stylized, vibrant art directions.

Parameter	Value
Slope	(1.0, 1.0, 1.0)
Power	1.35
Saturation	1.4

Settings reference

Setting	Type	Description
AgX Look	Enum	Default / Golden / Punchy

When to use AgX

• Realistic or photorealistic projects
• Scenes with very bright lights, emissive materials, or direct sun
• When ACES causes unwanted hue shifts or hard clipping in highlights

Reference

AgX is based on the minimal implementation by Benjamin Wrensch: iolite-engine.com/blog_posts/minimal_agx_implementation