Lightmap Build effect materials

Hi all,
i am making some nocturne snowy scene and
i am a bit lost on some behaviour i got from my opaque material.

I added a light from above , and i baked / build the light on it from unreal,
and then i turn off the light.
You can see in the image below the result of the lightmap save on the model,

while i understand that setting “movable” will bake nothing ,
and setting it to “static” , will bake the light completely ,
What exactly bake when is stationary?

Can i access this data from the material like i access the “vertexcolor” ?
i mean can i make a parameter to tweak this “lightmap” from black to grey and white?

and why the light seems came from under it in the middle image?

Bounce lighting and shadows (if enabled). Direct lighting and shadows for dynamic objects will still be dynamic. For stationary directional lights, cascaded shadow maps will replace all static shadowing near the camera.

No. But if you bake ambient occlusion, that can be accessed via the material node “PreComputedAOMask”

Looks like you have the directional light intensity turned down/off so it’s only being lit by bounce lighting.

Thank you very much !

Its very clear and very confusing too, haha

I think you are right, its lit from indirect lights bouncing.
I am surprised