In Dying Light multiplayer you see each other's flashlights complete with dynamic shadows and all

And it causes no performance hit. Not a single fps.

How is that possible?

The only other game I know which does this is Interstellar Marines (made with Unity), but in that game seeing another person's flashlight causes a massive performance hit, just like I would expect.

However, in Dying Light my friend can shine his flashlight on 50 zombies and objects and I can see them all cast dynamic shadows on my screen and I can even enable my own flashlight at the same time and there's no performance hit at all.

Mind blown? Can anyone shed some light (heh, pun) on this for me?

 

Dying Light is developed with the Chrome Engine 6 which uses deferred shading (http://en.m.wikipedia.org/wiki/Chrome_Engine).

Deferred shading renders the whole scene once and applies lighting in a second pass. In traditional forward rendering every object needs to be redrawn as many times as the amount of lights the object receives thus increasing drawcalls and rendering overhead.

The downside of deferred shading is that it has issues to render transparency. But this can be solved by using screen door transparency or drawing this object in forward mode.

 

Yeah, but I thought we had that in Unity as well? All my games are made with deferred: http://docs.unity3d.com/Manual/RenderTech-DeferredLighting.html

 

I think there is a difference between Deferred Lighting and Deffered Shading, but I could be wrong. Currently Unity uses a "Light prepass" but I heard rumors that they will switch with Unity 5 to a full deferred shading system.

Furthermore I think Unity's implementation is pretty old and I would not compare it to a system used by an AAA title which is pretty optimized and up-to-date for the task.

 

Okay, thanks for the replies.

The effect in Dying Light is amazing at least. Being able to turn on your flashlight, light up something and tell your friend to look at it is insanely immersive.