According to @PatrickRyan’s previous post:
A light map is the opposite of a shadow map in how we multiply its value with the incident lighting on a surface to calculate how it is lit. While the dark (0) spots on a shadow map represents parts where we want our baked shadow to subtract (i believe it’s actually multiplied) from the lighting on the surface, the lit spots (1) on a lightmap represent where we want light added to the surface in addition to the incident light.
If we look at your original post:
we can see that when you use your baked map as a light map, the renderer brightens your object interpreting the white areas as lit, while used as a shadow map, the renderer darkens the areas based on how black the image is in the given area.
It sounds like you want to use baked lighting, and baked shadows in combination to simulate the complex lighting in your scene sourced from a series of windows, and the objects in scene that occlude that light.
My personal sugestion would be to use a lightmap to simulate the light in your scene, combined with an ambient occlusion map that will darken your floor where your other object’s shadows would fall.
I’m not too knowledable of a good workflow in Maya to generate these maps, but I’ll ping @PatrickRyan if he knows of a good workflow to generate both maps in Maya, or if there’s a better approach to combining baked lighting and shadows.