How to create Ambient Probe data?

This might sound like a strange question, but for some reasons I would like to swap the RenderSettings.ambientProbe data with a custom one. (Because we are not using lights-map or baked GI, I believe they are past as spherical harmonics to shader, and then use in combination with Reflection probe in PBR shading.)

The problem is, I believe ambient probe contains diffuse data from skybox: but I really don't get how SphericalHarmonicsL2 class allow us to generate such data?

So say I have 2 skybox each will obviously create its own ambient probe data, how can I swap them?

(This is obviously a different question from swapping light maps, because you only sample ambient probe when both lights-map and custom light probes are missing.)

Thx in advance!

 

Wait, I was silly to have overlooked the AddAmbientLight method, I don't know how Unity devise the color from skybox but at least I can approximate ambient color now, that's good for now.

 

How did you resolve this? I'd like to change the ambient light only for specific indoor environment area. I am not a good programmer