I don’t understand how the lighting & materials work in UE4. Is the Skylight the same as in ToolBag 2, and the directional just another type of default light? If I completely remove the Directional out of my scene and set the Skylight to 0 intensity, my scene is still lit after light baking, how is this possible? What’s lighting my scene? Or maybe I should ask, what minimal lights are necessary to correctly light a level?
Directional light is exactly what it sounds like, it’s a sun in your level, or any other light source which is far away and casts parallel light rays. Not sure what default light you’re talking about, you might use it and might not use it, depends on your needs. 99% of the games mostly to use one directional light if the pipeline is dynamic.
Lightmass also computes ambient lighting, so even if you have no lights on the scene, scene will be lit with some lighting by default, change Environment color in World Settings inside Lightmass settings category.
Regarding skylight in marmoset, i’m pretty much sure UE4 skylight is somewhat similar to the one in marmoset, as the technique behind skylight is the same everywhere: environment map.
If I completely remove the Directional out of my scene and set the Skylight to 0 intensity, my scene is still lit after light baking, how is this possible?
If your lights have Stationary for the Mobility property, then the Intensity property is only controlling direct lighting intensity. IndirectLightingIntensity controls the bounce lighting. The reason for this is that only the direct lighting can be changed at runtime.