Re: [Flightgear-devel] Frame spacing and OSG: about to jump down a rabbit hole

[James T. <ja...@fl...>]

> On 6 Jan 2023, at 22:03, Andreas Mueller <alp...@gm...> wrote:
> 
> Regarding LOD in FlightGear:
> I have the impression that (different) LODs aren't used that much in FG:
> - terrain tiles and normal terrain objects only have one LOD
> - OSM buildings have only 2-3? LODs
> - aircraft have max 2 LODs.
> 
> Therefore my guess is that LOD handling isn't the culprit of performance problems.

There is some (understandable) terminology confusion here due to OSG : we don’t have many cases of selecting differently detailed models, but all the nodes and machinery around paging and loading tiles and models is in classes whose name contains LOD, especially the class PagedLOD.

The key parameters there are setting view distances at which the content referenced by the PagedLOD is loaded, and determining when (due to culling / being too far away) models can be unloaded. Even when the PagedLOD only has a single ‘detail level’, all that machinery and parameters are exactly what drives our loading schedule, memory consumption and therefore quite a bit of our performance.

Kind regards,
James