Questions about lightmass


I’ve started trying out lightmass finally for no particular reason but the results I’m getting are quite, bad honestly.
Here’s a rock lit with dynamic directional light and skylight. In the next image the only difference is that directional light is set to static.
Rock lightmap is 512. Scale is around 2 meters. Lightmass settings at default with 100 bounces. Production quality.
Is this generally how lightmass treats organic surfaces?

Is there a particular problem?

Not sure if this is still a thing but i would recommend to set the directional light to stationary otherwise you lose a lot a reflection / roughness informations.

When baked the rock looks like low poly without normal map. All details are lost.

@**A-J-K, **Tried stationary, results are very different from static. Normal details are back, although it still looks better and more detailed under dynamic light.Thanks anyways.

If I delete the skylight you can barely see any bounce light from the floor lighting up the shadows. Is that just how it works out of the box?

The problem with a static light(aside from the lack of a specular component) is that it’s entirely dependent on the Lightmap resolution and layout. 512x is a high resolution, but is the layout any good? I could UV a box with everything laid out in a small corner, then up the resolution in-engine to 2k, but it’ll still be pretty poor. There’s also an option to use the Normal map when baking static lighting, but I forgot what that does since it’s off by default. I think it was meant to help with normal directionality in the diffuse lighting…

The stationary light looks better because the direct light is no longer baked to the Lightmap. You’re probably also missing the shadow details from the geo since the stationary sunlight doesn’t have CSMs enabled by default.

As far as indirect lighting goes, it’s highly dependent on the material’s Base Color that is bouncing, the material’s Base Color that is receiving the bounce, and the overall light intensity. Try a flat mid gray material(0.18 or 0.216) and see what happens, or just full white on the ground and you should definitely see a bounce. Also switch to the lighting only view and disable any SSAO/DFAO you have enabled - the dark Base Color will make it harder to see the bounce and the AO will overdarken areas. If you’re happy with the visual aspect of a Base Color but want to increase the bounce contribution, I like doing that per mesh in their respective Lightmass settings for Diffuse and Emissive contributions.

This is more or less expected. To get the same amount of details, you would need to enable bUseNormalMapsForLighting and bring lightmap resolution on par with normal map res. At this point it becomes useless.

That is a great example why you should never use static lights unless you absolutely need to. The recommended default has always been stationary, not static :wink:

About the bounce light from the floor, i guess a big part of your problem is the dark standard texture you have applied on the floor. This kinda dark material will “eat” a lot of the light information.

Hi all,

Thank you so much for all the great information.
Without DFAO and without SSAO with floor being 0.18 I still barely get ~5% bounce light in the shadows there. I tried it with a pure white floor and now I get some light in the shadows but the floor itself is still not lit up at all as if there are no lights getting re-bounced from the rock to the surface itself. Is that expected behavior with even bounce lights set to 100?

You might need to increase the lightmap resolution of the ground, it might not have enough detail in that shadow to bounce back on the rock. You’d still need to have a skylight though for extra illumination in the shadows

Here’s the result with 1024x1024 lightmap for both rock and floor with directional light intensity of 7. I wouldn’t want to compensate with a skylight though and I think directional light alone should illuminate this pretty well, but also not sure it’s not.

If it’s supposed to be outside then you’d need to use the skylight, the atmosphere is illuminated which adds lighting to the shadows which is what the skylight is for.

Imagine there’s no sky at all. It’s a case of why one light source isn’t giving enough bounce lights from a white surface to illuminate the shadow. I tried with setting quality to 2 and shadows got a bit darker. I’m going to try various other settings, but I was expecting lightmass to do more than this out of the box. It currently looks like a single bounce from surface to back of the rock and then nothing bounced back to the surface itself.

A few things though
-again if it’s going to be outside then you need the skylight
-your exposure is low, which will make the shadows darker
-between the shadow and the darker color of the rock it’s not going to be all that bright in the shadow anyway.

I wish there was a way to bring back the baked spec (and multi directional bouncelight) that was available in Unreal Engine 3. (Before Lightmass)
Normals lit only with indirect light (and static direct light) could look so much better with it. :frowning: