Custom Lightmap Texture?

Is it possible to do global illumination / ambient light using a custom texture? Mapped out along the world X&Y axes? Applied to both static and dynamic objects.

I’ve done this approach before with OpenGL shaders so I could specifically paint colored lighting into specific places in the scene and have other areas darkened. Especially useful on mobile.

Using this for a sports field, where I want lighting focused on the field with colored sections, with the background getting darker. Ideally without fog or point lights.

lightmap2.jpg

You’d have to do something in your material, there isn’t an easy way to modify the lightmaps