Why does static and movable lighting look so different on static objects?

I’m trying to make my game run on lower end devices aswell, and i noticed having my skylight and directional light set to static instead of movable adds like 20fps to my total frame rate. This is a very big change, and i am pleasantly surprised. I am wondering though, why do the 2 look so different? Changing my skylight and directional light to static and then building lighting makes everything extremely dark, and changes the way everything looks (in a really bad way). In theory, shouldn’t the 2 lighting types yield the same results visually on static objects? How can i get my static lights to look more like movable ones?

The main difference is the lack of specular reflections. This is more pronounced when you set the skylight to static, because when you have a stationary or movable skylight it is used as the default source for specular reflections in areas not under a reflection capture influence. If you use all-static lighting you must use at least one large reflection capture to have any specular reflections at all, otherwise all your materials will look as if they have zero specular.

As to why this is so: when you set a light to “static” it’s effect on the objects is precomputed during lighting build and stored in textures called “lightmaps”, which store the amount of static light hitting the surfaces they cover. This is why a static light is “free”: they just get painted onto the lightmaps and don’t exist at run time. While the lightmaps can store some light direction information (the “use lightmap directionality” setting) to make normal maps show up under static lighting, it’s not usable for calculating specular reflections.


I’d say the main reason is that movable lights don’t generate GI but static lights do!!!

Baked lighting will give you a good FPS as there is no lighting computation at run time, all of the lighting information is stored in “Lightmaps” using Lightmass and you get some neat GI bounces which gives you really nice color bleed and changes the look of the game drastically.

As mentioned above static lighting simulates GI while Dynamic lighting does no such thing and is computed at run time that’s why it is costly than Static lighting. Also like @Manoel.Neto mentioned you need to add reflection captures for Static lighting.

I guess you can switch all lights to Stationary other than Sky light (Keep it Static) and you would have nice GI and your movable actors will also react to the lighting like your static actors do.

Hope this helps