Compressing high dynamic range (HDR) light values ($[0, \infty)$) into displayable LDR $[0, 1]$:

1. Reinhard: vec3 ldr = hdr / (hdr + vec3(1.0)); (Simple, but washes out color saturation in bright areas).
2. ACES (Academy Color Encoding System) Film Curve:

vec3 ACESFilm(vec3 x) {
    float a = 2.51f;
    float b = 0.03f;
    float c = 2.43f;
    float d = 0.59f;
    float e = 0.14f;
    return clamp((x * (a * x + b)) / (x * (c * x + d) + e), 0.0, 1.0);
}

ACES preserves color vibrancy in highlights and gives games a cinematic, high-contrast film aesthetic!

ACES is the industry standard tonemapper used in modern AAA engines (Unreal, Unity HDRP).

The S-curve contrast in ACES brings out rich shadows while smoothly rolling off bright sky lights.