Ambient light, probes and fog

Each scene stores one RenderSettings object (class 104) with its ambient lighting, fog, skybox material, reflection settings and the sun. The ambient lighting a surface receives comes from one of three sources, chosen by m_AmbientMode. Sourced · Unity scripting reference

m_AmbientMode	Name	Light comes from	Confidence
0	Skybox	the ambient probe m_AmbientProbe, generated in the editor from the skybox	Sourced · Unity scripting reference
1	Trilight	a gradient of three colours: sky, equator, ground	Sourced · Unity scripting reference
3	Flat	the sky colour alone	Sourced · Unity scripting reference
4	Custom	the probe, generated from a custom cubemap	Sourced · Unity scripting reference

The three colours (m_AmbientSkyColor, m_AmbientEquatorColor, m_AmbientGroundColor) are stored in every mode. In skybox mode they are whatever the scene last held for trilight, which is Unity’s default when never set: sky (0.212, 0.227, 0.259), equator (0.114, 0.125, 0.133), ground (0.047, 0.043, 0.035). They are not authored light. Proven · SkateBIRD, Sledding · every skybox-mode scene of SkateBIRD and of Sledding Game build 25351629 Observed · PEAK

The probe

m_AmbientProbe is a spherical-harmonics probe of nine coefficients per colour channel (27 floats: red 0 to 8, green 9 to 17, blue 18 to 26). It is what the editor last generated, which is not necessarily what the colours stored beside it produce: an all-zero probe means the editor never generated it. Observed

The band-0 coefficients (sh[0], sh[9], sh[18]) equal the average of the probe over all directions, in Unity’s packing of SphericalHarmonicsL2 (the canonical constant basis function after the Lambert convolution, factor 1). Sourced · Unity scripting reference In every skybox-mode scene of SkateBIRD and Sledding Game, m_IndirectSpecularColor equals those three coefficients exactly. Proven · SkateBIRD, Sledding It does in PEAK’s loose scenes too. Observed · PEAK

In trilight and flat modes the probe is not what Unity lights by, and a stored one can be stale: SkateBIRD’s level1, level3, level5, level7 and level12 store the identical probe although level7‘s trilight colours differ from the others’. Proven · SkateBIRD

Colour space and intensity

The colour space of the project decides how stored colours are read: the PlayerSettings of SkateBIRD, Sledding Game, PEAK and Big Walk all state a linear colour space (m_ActiveColorSpace 1), read as that one field (the Unity 6 players’ whole object is longer than its published layout, see type trees) and the same from an independent reader. Observed · SkateBIRD, Sledding, PEAK, Big Walk SkateBIRD’s player (Direct3D 11) writes its last draw of a title-screen frame into the 1920×1080 R8G8B8A8_UNORM back buffer through an R8G8B8A8_UNORM_SRGB render-target view, so the GPU encodes the linear result to sRGB as it writes it. Observed · SkateBIRD · one captured frame Under URP, the pipeline converts the ambient sky, equator and ground colours with CoreUtils.ConvertSRGBToActiveColorSpace, so the stored colours are sRGB-encoded whatever the project’s colour space; decoding is per channel like Color.linear, unclamped above 1. Sourced · Universal Render Pipeline source m_AmbientIntensity applies only to the skybox ambient source; trilight and flat colours are HDR colours used as they are. Sourced · Universal Render Pipeline source That Unity’s own trilight-to-spherical-harmonics blend is not in the published source is why the trilight result for the built-in pipeline is not verified against the engine. Inferred

Fog

m_Fog (on or off), m_FogMode (1 linear, 2 exponential, 3 exponential squared), m_FogColor, m_FogDensity for the exponential modes and m_LinearFogStart and m_LinearFogEnd for linear. Sourced · Unity scripting reference

What the games store

Sledding Game and PEAK store:

Scene	Mode	Intensity	Fog	Probe average (sh[0], sh[9], sh[18])	Confidence
Sledding level0 Boot	skybox	1.0	off	(0.1803, 0.2257, 0.3069)	Proven · Sledding
Sledding level1 mountain, build 25351629	skybox	1.0	on, mode 3, density 0.002	(0.1792, 0.2244, 0.3062)	Proven · Sledding
Sledding level1 mountain, build 26054124	trilight	1.0	not recorded	not recorded; m_IndirectSpecularColor is 0	Observed · Sledding
PEAK level0	skybox	1.0	off	(0.1803, 0.2257, 0.3069); sky colour (0.9661, 0.7698, 0.4804)	Observed · PEAK
PEAK level1, level3, level4	flat	0.5	off, density 0.0035	(0.0127, 0.1238, 0.5654); sky colour (0.9804, 0.9804, 0.9804)	Observed · PEAK
PEAK level2	skybox	1.0	off	(0.1803, 0.2257, 0.3069)	Observed · PEAK

A flat-mode PEAK scene stores a probe whose average is a blue (0.0127, 0.1238, 0.5654) unrelated to its white flat colour, so its probe is stale. Observed · PEAK The table covers PEAK’s five loose scenes; the 208 level scenes in its AssetBundles are not measured. Observed · PEAK Sledding Game’s lodge is inside the mountain scene and shares its RenderSettings; the scene stores one ambient. Proven · Sledding In build 26054124 level1 stores trilight mode with no skybox material: sky (0.6392, 0.9581, 1.0189, alpha 1.5), equator (0.7065, 0.9223, 1.0189, alpha 1.5) and ground (0.3532, 0.4612, 0.5094, alpha 1.5), HDR colours used as they are, with intensity 1. Observed · Sledding Build 25351629 stored skybox mode with Unity’s default trilight colours. Observed · Sledding

SkateBIRD

SkateBIRD’s scenes, by build index (the trilight colours are sky (0.5647, 0.5972, 0.6795), equator (0.7835, 0.7835, 0.7835) and ground (0.5457, 0.5457, 0.5457) unless noted; intensity 1.0 everywhere, fog off, fog mode 3, density 0.01 unless noted):

Scenes	Mode	Probe	Notes	Confidence
0 title, 1 bedroom 1, 2 rooftop, 3 office, 4 server room, 5 bedroom 2, 12 playground	trilight	stored	the colours are as stated; the probe and skybox differ per scene	Proven · SkateBIRD
6 credits	trilight	all zero		Proven · SkateBIRD
7 flashback	trilight	stored, identical to bedroom 1’s	sky (0.5621, 0.5986, 0.6765), equator (0.7206, 0.5195, 0.4716), ground (0.5441, 0.5441, 0.5441); fog density 0.06	Proven · SkateBIRD
13 skate heaven	trilight	all zero		Proven · SkateBIRD
8 loading	skybox	stored		Proven · SkateBIRD
9 MasterAudio, 10 Win10 Platform, 11 Steam Store Platform	skybox	all zero		Proven · SkateBIRD

Fog is off in every SkateBIRD scene. Proven · SkateBIRD

Reflections

SkateBIRD’s scenes store the reflection source Skybox with intensities 0.344 (bedrooms, rooftop, office, playground, skate heaven), 0.548 (server room) and 0.0 (flashback), and a subtractive shadow colour (0.42, 0.478, 0.627); each scene has 1 to 23 reflection probes (the office has 23). Proven · SkateBIRD

PEAK

PEAK’s levels light their surfaces from globals that its scripts set when a level starts, not from RenderSettings alone: Observed · PEAK · the managed scripts read, and level 4’s volume rebuilt

• FogShaderParams.Start sets the global texture FogTexture.
• LightVolume.Start, when the light map’s RGB and alpha slice arrays are both non-empty, rebuilds the light volume: each slice is a BC6H texture (RGB) and a BC4 texture whose red is the alpha, read with GetPixels and written with SetPixels into an RGBAHalf Texture3D with no mips (rows in Unity’s order, not flipped), which it binds as _LightMap. It then sets _Brightness, _AmbienceStrength, _AmbienceMin, _GridRes (x, y, z, 0), _RaySpacing and _GridOffset (w 0), the grid size and offset copied from the light map. These slices are the unnamed one-level BC6H and BC4 textures of the level bundles (textures) Inferred · PEAK · from the pairing and their equal counts. A reader assembling level 4’s volume (576878) this way gives the editor’s RGBAHalf bytes slice for slice.
• FogConfig.Start sets _WeatherBlend to 0. _WindTexture and the Wind* globals are set only by FogConfig.SetFog, which only StormVisual.LateUpdate calls, while the observed character is in a storm zone whose wind is on; at a level’s start no script sets them.

A LightVolume’s script data is 188 bytes plus 12 per slice reference, and a FogConfig’s 84 bytes (its private sinceSet is not stored). Observed · PEAK

In the Unity editor (6000.6.4f1, linear colour space), a global texture (2D, 3D or cube) that was never set, or was set to null, samples as (0.2158203, 0.2158203, 0.2158203, 0.5019608): 128/255 decoded from sRGB in RGB and 128/255 in alpha. A global float or vector never set reads 0. Observed · probe shaders in the editor