LODs and Realtime GI

Unity Engine
1

Hi,

I know there’s been a few subjects on the issue but I’m still struggling to wrap my head around it.
I just can’t seem to get good GI on my LODs.
and before I get yelled at, yes, I did read the documentation Unity - Manual: LOD and Enlighten Realtime Global Illumination

So, a breakdown of the different parameters to try and rule out as much as possible:

  • realtime GI only ON (unity 2017.3.1f1)
  • standard LOD setup for that object
  • lightmap indirect resolution is set to 1
  • object’s UV Charting Control parameters are all default
  • scene’s Ambient Color is black
  • Indirect Intensity in the lighting panel is at 1
  • lightprobes are setup quite compactly (for the sake of this example)
  • all lods are set as static (if I understood correctly, the LOD1+ will default to lightprobe anyway)

This is the result for my LOD0 and LOD1+

2124×1121 743 KB

lightprobes:

730×845 459 KB

The pop between LOD0 and 1 is quite visible (even more so in a proper scene) and if I ever was to raise the indirect intensity, oh boy…

So am I doing something wrong? Isn’t there any way to ever get the lods to work while using realtime GI?

Thanks in advance!

2

Hello! Your scene and gameobject setup seems fine at a glance. I have just tested on my machine, and lower LODs do sample lightprobes correctly. Keep in mind that lightmapped objects will still have higher precision lighting information, as opposed to the ones lit by probes.

The .gif below (direct link - https://oc.unity3d.com/index.php/s/izBJZqXGrIpinXw) shows a simple Cornell Box scene, with two cube meshes. The static mesh on the left contains two LODs, while the mesh on the right is dynamic, and is lit only by probes. Ambient Color is also set to 0, just like in your scene.

You can also check whether or not your probes look correct after baking the scene. Navigate to Lighting > jDebug Settings > Light Probe Visualization and select your preferred way of visualizing the probes in the scene view.

I hope that helps.

Sincerely,
Kristijonas

3

Thanks for the answer.
So I guess it means that it’s quite unlikely that it would be usable aside from specific lighting conditions where light/shadows contrast is fairly low. (ie: low indirect lighting). That or on small objects on which you might not notice the pop.
In my case it’s fairly big rocks (~10m) with a fairly strong direct light, so I guess I should give up trying loding those? I mean at that size, even if the LOD1 is far away, its unlikely that you won’t notice the pop.

4

There should be no reason for you to not use LODs on your rocks. The problem most likely stems from your particular lighting setup. I have yet again tried to replicate a scene that is reminiscent to yours, and the lower LODs receive proper indirect lighting from the probes. Please see the .gif (direct link - https://oc.unity3d.com/index.php/s/IzcpWt8HM33imY6/download) below for demonstration:

One of the reasons on why you might not be seeing indirect probe lighting on your LOD1 mesh is the probe placement. If you have a lot of probes which are intersecting the mesh (and thus they turn black in the process), you might be interpolating between very dark, and bright values, which may cause you indirect to look dark.

Also, keep in mind that in order to get nice indirect lighting in the outdoor scenes, you should avoid using black as your ambient color.

If you need to use black as your ambient color for any given reason, keep in mind that you would then need to boost your light’s Indirect Multiplier, along with the Indirect Intensity in the lighting settings. However, doing either of those things is not recommended, as it boosting those values will no longer provide you with physically correct lighting.

If you want, you could create a small project, which reproduces the issue you are having. You can send the link via a private message so that we could take a look.