Foliage static lighting intermittently fails
I have a lingering (also in UE 4.9) problem with my (hand-placed) foliage static lighting occasionally failing, raising the 'lighting need to be rebuilt' map error and causing the foliage to be dynamically lit, which looks terrible and causes terrible performance. The problem then persists with every build, but (I think) occasionally fixing itself.
I don't know what causes it and I don't know what (occasionally) fixes it. Usually the problem arises after I've tweaked or imported a static mesh or two while incrementally improving/filling a level (possibly while fiddling with static lights) - nothing to do with foliage. Migrating to another project and/or upgrading the engine fixes it (for a while) but rebuilding the lighting with "Force No Precomputed Lighting" set and then unset does not fix it.
In the first picture, the problem is shown in the upper part; the lower part is the lighting when it is working (the grass looks a bit rubbish generally, but that's another problem...).
The other pictures show my lighting settings on a typical foliage element (said grass), in my world settings and in the editor settings for rendering. I have a stationary directional sun light, and my remaining lights are all static. When I do a DumpUnbuiltLightInteractions, the five instanced foliage meshes appear, as does every single one of my static lights (including those which do not seemingly encroach on the foliage). The foliage lightmaps are all set to 8, with 1900 or so foliage elements placed in total, so the lightmaps are not crazy big.
As an aside, I have Hierarchical LOD turned off because turning that on causes a rendering error with one or two of the speedtrees that I've imported (that may have to be a separate query but perhaps is related).
Any suggestions welcome - for performance reasons I can't switch to dynamic shadows (I tried, and I don't think that fixed it either).
PS all the foliage actors are standard Speedtree imports from standard Speedtree packages - to my recollection I've not touched a thing.
PPS this seems a similar issue but was not followed up https://answers.unrealengine.com/questions/290753/worldsettings-1-error-lighting-needs-to-be-rebuild-1.html
I have added this thread to the list of issues regarding static lighting caches only being derived from one source along with adding the issue of static light calculations in larger foliage scenes.
The ticket number is UE-20029.
Again, I do not have an ETA for when this issue will be resolved or how quickly it will gain support.
Thank you very much for reporting this issue to us.
answered Nov 19 '15 at 02:49 PM
Follow this question
Once you sign in you will be able to subscribe for any updates here