I’m trying to understand the behavior of skylight for indoor or shadow areas for moving objects and i’m getting some strange results.
Here’s a simple scene test (in 4.11), a closed box with two spheres in it, one is movable the other is static.
The scene itself contains just the regular empty start scene with a sunlight and skylight/skysphere, detail settings: epic - lighting build: production - lightmass importance volume.
All lights set to static stationary.
No reflections
I have global post process volume with auto-exposure settings turned off just in case.
Lightmass environment color is set to pure black: (can anyone explain to me why this is set to light blue color by default, it produces an ambient light outside the control of your actual lights in the scene, isn’t it better to keep the actual lights in the scene for the ambient light control instead of having lightmass have a separate ambient color being added to whatever lights you have in there?
As you can see the skylight is affecting the moving objects inside the cube when it’s supposed to be pitch black.
Even if i set my stationary lights to intensity of zero, there still seems to be a slight ambient affecting the moving object.
I may understand this behavior if the skylight was set to “movable light type” since it may not be able to do real time soft shadows for moving objects and depend on AO if i’m not wrong which is not enough, but this is set as stationary, isn’t it supposed to bake the light in the lightmass and have proper color bleed and shadows? and why is there a slight ambient light leak onto the moving object when all light intensities are set to none.
Sorry to bump this thread guys, but it would be great to have an overall idea of how this works in general and how to correct the light exposures for the moving objects. Any workaround or help in understanding the way skylight is working here would be much appreciated! Thanks again and sorry for the bump, but i’m kind of puzzled here.
This is a very small space you’re placing a movable object in, and the lighting changes very quickly. It’s not going to be accurate. If your skylight is static, it uses Lightmass. If your skylight is movable, it uses a reflection of the sky. If it’s stationary, it uses both.
Lightmass calculates not only the static indirect lighting for stationary objects, but also a full-blown lighting cache across the level and in the air for movable objects: the indirect lighting used on that object is the closest cache to the object. In order for the cache system to work properly, you need to place at least one lightmass importance volume: the caches will be placed within the volume. But it’s only accurate to the nearest 3 meters. On the top of the viewport, click View >Visualize > Volume Lighting Samples to see the indirect caches.
The skylight will also take a generic reflection from the sky and map it onto the reflection environment of all objects within its radius.
In one of your examples, it looks like it took the lighting cache when the lighting is at full intensity. At 0 intensity, it looks like it still calculated the reflection. Even materials that are completely black will still reflect light unless specularity is set to 0 in the material.
Thank you for the reply, I’m not sure if i understood the practice of how the cache is working in its entirely, but I will give the importance volume another try and let you know.
I went back to the basics, I removed the skylight for now, lets just have a single stationary sunlight, there is nothing else in there, plus i replaced the moving object with a figure to give you sense of scale.
I have lightmass importance and character detail volumes in there as you can see.
What am i doing wrong? how do you solve the issue if my character walks into a dark house/cabin from a brightly lit outdoors how to get rid of those light leaks plus the exposure issue on the movable object. Like I said no skylight here not even lightmass environment ambient color, that’s checked to black.
Also Is it possible to increase the lightmass samples density like the example below from the docs, right now they seem too far apart?
Ok, never mind i figured it out, thanks anyway, it was like you said a scaling issue, I had to scale things up further and figured out how to increase those samples for the indirect volumes, and its now working. Regarding the leak I fixed it by not having the box intersect the ground, I suppose the lightmap res on the ground was still not enough for that. It’s a bit of a workaround I wish it was better documented for beginners like us.