Does anyone else have a performance issues with - lets call it - modern NPC overhauls like Coldsun's World/Vision or Northbourn?
My issue is that my CPU time (as reported in steamvr timings window) skyrockets when viewing muliple (8+) NPCs where some of them were are modded via said mods. That's not the problem if there is like 2-4 of them in the viewport.
So i.e. standing in a corner of a bannered mare and looking at all NPC results in ~10ms of CPU time with a lot of late starts. But coming a little closer causes the CPU time to drop to something like ~5m. Also viewing them all but disabling just Olfina (from coldsun's world) gives significant boost. Much higher boost than disabling i.e. Sinmir (from some other mod, I dont remember which one. PAN? HP NPCs overhaul?). Removing Coldsun's world (so it fallbacks to some other mod) so also helps.
That shouldn't be a hardware issue issue since CPU is 9800x3d.
Have anyone noticed such thing? Is it caused by interaction with some other mod? From my testing its rather not something from Community Shaders suite, physics (CBP/SMP) or lightnings mod like Light Placer, True Light, DIAL, WSU, etc. FPS stabilizer doesn't help either.
I think it has something to do with hair meshes, since installing KS Hairdos SPID seems to drop the CPU time further.
OK, I need a little more testing, but I think I got this. This was kind of PEBKAC. I overestimated modern CPUs and Skyrim's engine.
My current theory is that you just can't have too many vertices in skinned meshes. And every one of my NPCs had high poly head with a custom hairstyle since I used a HP NPC overhaul as a base. And on the top of that was placed even fancier mods. My goal was to have every NPC de-bethesda-ized, but that kinda backfired. I'm pretty sure I did something like this in a flatrim on a worse CPU (12700k), but well, let's not expect too much from VR version.
Also different good looking hairdos can vary in vertex count quite a lot. So i.e. Olfina from Coldsun's World has hair with 38k vertices (KS Hairs), but Olfina from B and B NPCs has hair with only 8k (SG hair pack).
So my advice for every NPC modded is: use HP NPC overhaul as a base since AFAIK it covers the most NPC. Onto that stack some performance friendly overhaul that looks better than vanilla, but are kinda old-era and therefore lighter. Im am using Babes of Skyrim for now (it also covers males). And on the top place your favorite overhaul for a chosen "few" NPC, like Coldsun's or FarodaDestin (haven't tested perfermance of that one) or whatever's your thing. There may be more in between, but the idea here is that some NPCs in the crowded area must be "cheap".
That way I went from 10ms with a lot of spikes and late starts to something like stable 5ms while looking at all ~11 NPCs in Bannered Mare. Michael may not look as fabulous as he did, but Hilda still does. Priorities guys and gals, priorities.
You seem to have more technical knowledge than I, so you probably already ruled this out, but are the NPCs using SMP hair?
No, thats not a SMP fault. I thought of that at first too, but that turned out to be a dead end. Oddly enough, SMP or CBP seems to affect CPU time a little compared to the issue I described. I know nothing about Skyrim's engine pipeline, so I can only guess why it affects FPS so much.