POM, Tessalation and Bump Offset, when should i use what?

So after alot of time using only normal maps, I feel pretty ready to up my game, so had to learn alot of new words, and do alot of googling, but I feel i didnt realy learn that much, so I am now at the merchy of you UE4 lords, learn me to use the tools we get from Epic right.

I know tessalation got the biggest performance hit, so that one I am not going to use that much (got a 960 gpu), BUT Bump offset and POM is sounding pretty cool to use, but what are the perfomance hit of the two. If i want to create a plaster wall, and vertex paint som damage to it, which one would deliver the best effect for its resource cost? How much of it should i use and at what point would actual geometry be cheaper then a material effect?

I might be asking in a pretty dumb way, but every disscution i found online about this went over my head, so I guess i am pretty slow when it comes to materials and shader speak.

Bump offset: cheap.
POM: not very cheap off the bat (and better results make it less and less cheap as you go).
Tessellation: I’ve only ever found this valuable when making small, indoor, close-quarters scenes for demos and the like.

In general, I find most use cases for these three techniques — not all, just most — to be overkill.

mittense makes good points, to elaborate:

Bump offset: too many artefacts (too weird looking) to look good a lot of the time, even if it is cheap.
POM: Less artefacts than bump offset, but still there.
Tesselation: Once again, less artefacts than POM. Can have terrible artefacts if you get it wrong though, and get really expensive.

Most games, UE4 or otherwise, don’t often ship any of these. They can all be trouble to work with for results that range between ugly to too costly. But some ship, just experiment to see if it works for you.

Bump offset can look nice enough if you use Iterative BumpOffset. I came up with the technique long ago but oliver m (malkavian) explains it on his blog as well

if you have proper LODs you can make a version of the material that disables the expensive stuff entirely (i.e. with a StaticSwitch parameter) and only leave the full expensive version on LOD0. with such a setup I’d expect POM/Tessellation to be usable

Quake Champions uses POM btw :smiley:

Back in UDK times I also used the iterative BumpOffset quite a lot and liked the results. I actually never tried it out in UE4, though…
The POM is quite nice to me… of course it is not free of artifacts but if you put it in the right place it can give your materials a nice optical boost, imho…

I’ve actually had the best luck with a subtle bump offset here and there (mostly on lower-res and some terrain materials); it’s not as bad as it may seem at first.

And, really, I’d say while it makes for some really good scenery/environment screen shots, hardware tessellation using displacement maps is really the only technique I recommend very strongly against. It can have a good payoff, but it’s just not all that useful for production. The one exception I think would be worth mentioning is that water/ocean shaders can benefit from it fairly well.