I made a lot of tests involving ISM, I was convinced that ISM was cheaper than HISM for a long time.
I made some tests back in the days regarding this, and I remember ISM coming out winning.
I dont recall exactly what it was now, but i think it had to do when moving them.
Recently i made another test and HISM came out winning with 10x better performance…
Maybe something changed in the engine.
Could anyone explain exactly why and how is ISM more performant than HISM, if it is?
Here’s the things i already know from my research:
ISM vs HISM:
- Contrary to popular belief, ISM has LODs. The only difference is that ISM Lods apply to all instances and are calculated from the center of the ISM component.
- ISM doesn’t do per instance culling.
- HISM does Per instance Culling but it calculates all the LODS individually on each instance…
Now i think there is a difference when animating them.
Thats where i think the performance difference makes it worth it to use ISM rather than HISM.
In general it is recommended to use HISM if you are working with lots of objects spread all over the map.
But if you are working on clusters/groups of objects that are specific to one area, then ISM will do fine.
So if you have a group of cards on top a table, then a group of cookies, then a group of coins. All of these could be ISM and since they are separated but contained in their area their LODs will work for the whole group.
But if all of these were spread accross the room chaotically then their LODs would not work properly…
If that makes sense…
Anyone could give me more insight in this?
Why exactly is the ISM cheaper than the HISM, if it actually is?