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Need help to understand Dynamic lightning for an open world game

Development Discussion Rendering
#1

I just want to know if im on the right track, if the workflow is ok?

So i enabled light propagation volume as described HERE](https://docs.unrealengine.com/en-US/Engine/Rendering/LightingAndShadows/LightPropagationVolumes/index.html) Then i enabled distance field shadows and set cascaded shadow maps to 0.0 (i read somewhere that i shouldn’t use CSM for open world) Is this true? if so, is there another way to make the shadows dynamic?

Also not sure what the LPV size does 100%, if i decrease the value i’ll get better performance, but shadows get darker. what determines the LPV size?

#2

There’s settings for the LPV in any Post Process Volume(s). So if there’s 1 PPV, and 1 LPV, then the settings for that LPV are in the PPV. Checking each one enables them, and then change those to change the size. A size of 5000 is in UE units, so 5000 cm, or 50 m on a size of the LPV volume (cube). But with the post process volume, there’s the ability to blend those settings of the LPV into the PPV (Blend Radius, Blend Weight, Priority, and set it Unbound). While an LPV concentrates light to an extent within its bounds (50 m per side cube), decreasing the size is going to reduce the light propagation outside its bounds, resulting in darker shadows. Are the shadows also getting darker in the LPV?

#3

I also on good advice ( tim hobson I believe) said not to use CSM on large open worlds via world comp, is that still the case ? LPV are also not supposed to be used for such worlds, right ?
LIghting shouldn’t be this difficult.

#4

Why wouldn’t you use CSM with world comp?

CSM with an open world is pretty much your only option in Unreal, unless you also support Distance Fields for your meshes. At that point you could fallback to Distance Field shadows at a distance, but they most likely won’t be a viable solution for up close shadows given their limitations, but they’re triangle independent and therefore great for distant shadows.

#5

I tried this.

1 Movable directional light
2 Stationary skylight
3 Force no recomputed lightmaps
4 Enabled distance field shadows
5 Distance field shadow distance set to default 30000
6 Dynamic shadow distance movable light set to 4000

Is this setup ok?
The map is 4033x4033, should i use world composition for this size?

#6

With stationary skylight and “force no precomputed lightmaps”, there might be a problem or two of direct lighting from the skylight. 4000 is a lower value of dynamic shadow distance, but it could work depending on the game. That’s my hypothesis about that setup. I don’t know about world composition, and distance field shadow distance sounds short. yet it again depends on the game.