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HLOD having weird results.

Hello all, I working on learning optimization on a project. Unfortunately I cannot tell too many details but have resorted to posting here for help.

We have a small City that uses modular pieces to make the buildings. I have watched the unreal video training for HLODs which seem like a good option to reduce draw calls in our city. I made an empty level with about 10 buildings to run tests to make sure I’m doing it right. For some reason though after running the clusters and generating it seems like my draw calls are going up and my triangle count is almost tripling. I turned on the coloration view to make sure it’s switching out but something is not working the way I intend.
I was under the intention that up close would show the piece’d modular version and then as I move away it would switch to the HLOD combined building and then LOD further as it gets farther away. Perhaps I am using it wrong and would like to know thank you .

I have never really seen LODS done for a whole modular building other then by way of using a mesh merge technique.
How have you created the LODs?

And Do your modular pieces actually have LODs to reduce tris count when further away?

Also, you should look into Imposters for really far away stuff.
https://docs.unrealengine.com/en-US/Engine/Content/Tools/RenderToTextureTools/3/index.html
(tip:Post Page)

Also, if you have finalized your modular layouts you can actor merge:

Just keep in mind that when you get close your render cost is higher as you will likely not be able to occlude small parts like you would with a modular setup, and it will instead have to have the whole building out of view to have it occlude.

What I would suggest is to create building actors, and populate them with the modular parts. that way occlusion can still work, but you have “actors” as a building composed of many meshes.
Then from far away you can set the LOD for the modular parts to not exists, and an Overall LOD of the building mesh that’s comprised of the merged actors mesh appear as the replacement.
Not sure how much you’d be saving on drwacalls though. Running a test myself out of curiosity.

I thought about merging the buildings as well but there is plans for destruction so I guess it wouldn’t really work when your up close. But once you step away, switching them to merged version is what I thought would happen with the HLOD. Trying regular LOD for the modular pieces leads to noticable gaps between pieces . Once the HLOD mesh is created I tried LOD those and it worked great but still had higher draw calls and more triangles than the original modular ones.