Character lighting adjusts with lightmap on terrain and DIF, where?

I'm trying to find the section of TGEA that handles changing the brightness of a character when they step on bright or shadowed terrain and/or DIF interior.

I'm guessing there is a castray somewhere that detects proximity and reads the lightmap. I can't find it.

Any suggestions on where to look would be helpful.

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Found it.

sgLightManager
// Ambient light is determined by the surface we are standing on.