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lightmass for dark rooms?

hey, so I’m making a house for archviz, and in rooms that have lots of sunlight it’s quite ok, but other rooms that are only illuminated by the skylight, I get a lot of weird artifacts. I’m trying this for weeks now and lightmass only gives me bad results. I even manually mapped everything for light maps, and the results are still terrible.

I realize that it’s hard to get good results from a skylight, even in vray it’s bad as the only source of light (hence the existence of skylight portals) but what would be a proper way to do so? I can’t have the sun lighting the house from every direction, and I don’t want to bake lighting from ceiling lights as I wanted to be able to switch them on and off. is there a way to make a dark room look good? like what if I’m doing a night scene?

Ok so I realize there’s lightmass portals, and it does make a huge difference, see these screen captures:

3.jpg first image has no baked lighting, second one has no lightmass portal, 3rd image has a portal.

it did improve it greatly!

however, there’s a lot of color banding, you can see specially on the right wall. not visible on this image but theres quite a lot on the floor and the ceiling aswell, and another thing that bothers me is the black inconsistent shadow on the upper right corner on the 3rd image.

so the lightmass portal indeed helped a lot, but the quality is still beyond what I’d expect from light baking. I manually mapped uvs for the light maps, to make sure everything had the right proportions and pixel ratio, no overlaps, decent padding, and when I imported this scene with datasmith, I selected min 512 and max 2048 resolution, which I thought should be enough. I also baked light in production quality, and it stills is way below my expecations.

how can I improve it further? is it even possible?

Go in your world settings and uncheck the “Compress Lightmaps” toggle to improve (at the cost of higher memory use) your lightmaps. :slight_smile:
You can also tweak your lightmass settings by reducing the “Static Lighting Level Scale” value to 0.1 or even 0.01, up the bounce count for indirect and sky lighting to something like 10 bounces, and finally up the “Indirect Lighting Bounces” value for an even higher quality bake.

Another way to (drastically) improve your baked lighting is to use the GPU Lightmass made by Luoshuang.

Cheers,
Antoine