Light Complexity about Shadow

[Alundra]

Hi,
Here a quote from the documentation :

Light Complexity shows the number of non-static lights affecting your geometry. This is important to monitor, since only up to 4 non-static shadow-casting lights should be affecting a surface at any time. Any non-static shadow-casting lights beyond 4 will not result in accurate shadows. This doesn’t mean you need to remove lights, per se, but you should consider restricting the number of shadow-casting lights down to 4.

I would understand why upper 4 lights the shadow casting not result in accurate shadows.
Does that mean Unreal does 4 shadow map of 1024x1024 and for other lights he does an atlas based on distance ?
Thanks

[darthviper107]

No, you can have as many static lights as you want, but for stationary or dynamic lights you can only have up to 4 lights affecting shadows on a surface

[Alundra]

The documentation also said :

Any non-static shadow-casting lights beyond 4 will not result in accurate shadows.

I understand other light will cast shadow too but not accurate. Are they generated using atlas based on distance or half sized shadow map ?
Or you mean the renderer selects light based on distance and keeps the 4 who is near of camera and generate shadow map for them only ?

[pointcache]

Would be great if you tested that and posted results im interested in this too.
In unity there is “light importance” value that overrides distance culling.

[anonymous_user_f2b8b290]

Any non-static shadow-casting lights beyond 4 will not result in accurate shadows.

This is not accurate and I have updated the page. The light complexity viewmode just gives you an idea of how much GPU time will be used to shade the scene.

The only limit is that the first 4 STATIONARY lights affecting a surface will get precomputed shadows, which are very inexpensive. Any after that will use whole scene dynamic shadows, which are very expensive.

[Alundra]

Thanks for this precision about that. Does Unreal has an optimized way of shadow map using atlas or each visible light end to one shadow map of WIDTH x HEIGHT (1024x1024) ?