I am overwhelmed by the response from Lightmass developer himself - @DanielW. I want to ask like million things right now, but certainly that’s not possible. So I quickly created this Unreal project to ask for the solution to some of the basic/fundamental problem I (we all) are encountering during self learning of Lightmass.
In Vray or Corona we can visualize/see the actual samples taken into consideration for final calculation, which in turn gives us a chance to increase samples, size or filtering to remove blotches and noise from the GI. Also it is well documented how Light cache and Irradiance Map is working in Vray and we get individual settings for subdivisions and sample number/size (We have precise control over what is going on under the hood).
Unreal Engine’s lightmass is amazing when it comes to ease of use and speed, but critically lacks when it comes to provide precise control over GI calculations and that too with vague explanations without any proper example.
It would be amazing if we bring some the Values/settings in UI of Engine dealing with - Photons (Direct, Indirect and Irradiance). We need documentation about how the Photon mapping is working inside the Lightmass, covering all the relevant values which are necessary to produce clean GI with clear-cut contact shadows. There are too many values to understand from SceneExport.h and that too without backing of proper visual examples(It’s kind of impossible to understand these values without visual examples in engine)
Why we Architecture Visualization artist going for .1 or .2 values in Static Lighting Level scale? - To grasp all the intricate details in every corner of the space without loosing any contact shadows (Wide open diffused white walls are always difficult to deal). All Unreal Engine Architecture work is in direct competition with Vray and Corona, giving ultimate control for GI will certainly level the ground for all.
I believe all the settings are there to produce stunning results from Lightmass (Many artists have already proved it). But unfortunately that involves tweaking in BaseLightmass.ini, which make things somewhat hazy and unpredictable (Don’t know what values are doing exactly).
Here are the Visual Example of the problems faced by almost everybody during lightmass calculation. I tried few different combinations of lighting. Whole scene is being uploaded for sharing, will give the link ASAP.
Level one is only lit by Skylight with HDRI
These are the Lightmass settings -
All walls with Floor and Roof have 1024 Resolution. As you can see the quality is unacceptable, lots of blotches in dark areas. Areas coming in direct contact with skylight are well lit without bugs, all the problem is in dark areas where direct skylight is not hitting.
In second level I have put the stationary spot lights in corner to remove the splotches (hoping for the best). Lightmass world settings are same as above.
Using Spotlights with .1 value in Static Lighting Level scale almost always gives this infamous Light Leaks without improving the secne as much, rendering scene unusable. With 3 folds increase in rendering time.
Long build times are not so much of a problem if in the end we know what we are going to get (Predictable results).
Whole scene images -
Kindly Let us know -
How to remove the splotches in the area where there is no skylight hitting directly (Areas far from windows). As you can see in the above images there are so many splotches in gallery, despite having Indirect Lighting quality to = 10 and static Lighting Level scale = .1
Shadows become somewhat messy after a certain distance. How to make area shadows more clear and smooth.
Whenever we put spotlights to remove dark areas, it almost always gives the annoying problem of light leaks. Clearly evident in the above images.
What are Direct Photons, Indirect Photons and Irradiance Photons in relation with Lightmass and there respective uses in GI solver.
Unreal Engine Architectural Visualization Community