UDK dynamic lighting problems

Obscura

Hi.I started a new environment in UDK, and i wanted to use fully dynamic lighting with no pre computed shadows (without lightmass).The problem is, when i deselect the light source, all of the shadows are dissapears.I tried different types of lighting sources, but i always got the same result.No casted shadows.Just Vertex lighting.Help me plz.

JamesWild

In UDK, you can only really have one dynamic light with shadows. This is the "dominant" light source. Usually the light used is a DominantDirectionalLight.

It's way too expensive to have more than that - even games like Skyrim use pretty much only one dynamically shadowed light at a time.

Obscura

thanks for the reply, but this doesnt solve the problems about shadowing.All of the shadows are only visible when the light source is selected.I checked Force no Precomputed lighting, but it doesnt helps

ambershee

If you use non-dominant lighting you can have multiple shadow casters.

Obscura

I used a simple point lights, but the light type is doesnt matter, there are no shadows:(

Obscura

JamesWild

Yeah that's intentional it's to give you an idea of where the shadows will fall when light is built. If it did it for all lights in the scene it'd be utterly unusable.

I'm not seeing why this scene needs fully dynamic lights and shadows yet...?

Obscura

sorry,its my mistake, not dynamic lights, but realtime shadows!

JamesWild

Realtime shadows are where a dynamic light is occluded. You can't have a static light with dynamic shadows, short of storing a different lightmap for every light in the scene!

Obscura

So i can meke realtime shadows only with dynamic lights?You said i can use only one dynamic light.But i want to make torches to the walls.with 4-5 light source, and with realtime shadows.Which type of light source is good for this?With what kind of parameters?
Thanks for the replies

JamesWild

Typically you'd only have one light in a scene casting realtime shadows, the dominant light. (usually given to the sun or, in the Mages' College in Skyrim, the Eye of Magnus, for example) The issue is that it has to redraw* the scene from the perspective of each light (twice for omni lights, possibly) so it's not a cheap operation, and having 4-5 lights with realtime shadows would be absolutely killer for performance. When it comes down to it a dynamic shadow is basically a dynamic light with the exception of some nasty techniques like pre-Lightmass UE3 used (which darkened all fragments below players' meshes, looked terrible) so you're gonna need an alternate technique.

If you know what's going to be casting the shadows like the torch holder, you might be able to get away with synchronizing a moving Actor with the flickering light source to fake a shadow.

*it's a depth-only draw, so it's pretty easy on the GPU, but the CPU/CPU+GPU bridge takes a similar amount of stress as if you were redrawing the whole scene in colour.

Obscura

I tried the realtime shadowing with 4 point lights, and it was absolutele preformance killer. There was only 4 FPS :S So i changed the lighting method to the lightmass based, and it works fine. But what if i want to make, an openable door?

Minato

That's where Light Environments come in,they create an approximation of all the light sources that affect your object using what's called a Spherical Harmonic light or SH for short,and a directional light,in the process it also creates what's known as a composite shadow(which is generated by the directional light component of the light environment,and it's direction is determined by the brightest light source that affects the environment),it's not an accurate methode for shadowing but it's more efficient...