day night cycle with baked light? (lightmass)

is it possible to create day night cycle with baked light using lightmass instead of light propogation volume? (with GI)

It’s not possible because of the Cast shadow. If you bake your light in a special moment, your shadow wich is bake won’t move, also if you move the sun, you will see your cast shadow (baked) + your direct light from your sun

Hi LTE,

If you’re using a Day/Night cycle dynamic lighting is the only way to effectively accomplish this. Lightmass and baked lighting is intended for scenes/levels where the lighting will not be changing in this manner.

Dynamic GI right now is also considered experimental with LPV. There are some improvements that have recently been checked in that will make it into the 4.9 build. All the code changes for that are also coming from Lionhead Studios and is not anything that Epic is developing here. We have our own method Distance Field GI that you can read about here, but this is also considered experimental at the moment as well.

I hope this helps.

Tim

isit possible to have baked shadow, but i wan dynamic lighting that wont affect the baked shadow? Coz I have a city environment which is too costly for full dynamic light

Shadows don’t exist without light. If light is fully dynamic you can’t have static shadows.

I guess he is talking about “stationary” lights. Kind of in between dynamic and static lighting.
There you cab change color and such, but shadows are still “baked”…

Yeah that would make sense. It seems bit artificial restriction that indirect light properties can’t be changed on runtime. It would make sense to always bake lightmass with default brightness and white color and then just tint and rescale it at runtime in shader.

“Stationary Lights are lights that are intended to stay in one position, but are able to change in other ways, such as their brightness and color. This is the primary way in which they differ from Static Lights, which cannot change in any way during gameplay. However, it should be noted that runtime changes to brightness only affect the direct lighting. Indirect (bounced) lighting, since it is pre-calculated by Lightmass, will not change.”

That idea makes no sense. Then you would need to know in the lightmap from each pixel how much each light affected it. Then you are basically re applying the lighting for each pixel dynamically and what was the point of storing lightmaps in the first place?

The point of lightmaps is to precompute the expensive part about scattering light. Once they are made, the lightmaps have no knowledge of where the light came from and that is by design. The exception is shadowmaps from stationary lights, but still the indirect light is separate.

I guess it would be a separate technique where every light has its own lightmaps for every object it affected so that you could dynamically composite them. Something like that would be really expensive though. We will probably see better functioning realtime GI before we see that.

+1 I lol’d

Sorry my bad. I was only thinking non general case where there is only one light source.

Rereading my post, I did not intend to have such a negative tone. There is nothing wrong with the idea on a concept level I just meant to communicate the difficulty in setting it up that way.