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Using LODS

E

ErlandMatz

Messages
24
Country
sweden
Hi there!!
I just wonder if it exist some standard for WHEN to use LODs?

When I Created the Church nearby my home in Gnesta Sweden - I used LODs for the first time and it works fine.

In LOD0 I have 87000 verts.
In LOD1 I reduce that to 40000 verts
In LOD2 I reduce that to around 10000 verts and replaced all PBR with colors.

But I wonder if it is really needed. When I test the FPS on my computer. I have a Geforce RTX 4070 Laptop GPU. CPU = i7 2.10 Ghz and 32 GB memory
and it is always perform 60 FPS.

When I stand on Heathrow my FPS is 45 with clear skies and 35 with rain.

I also have modelled my area of living in Gnesta a community with 9 houses with 4 flats in each house.
Totally I have 12500 verts per house - Nothing indoor. Just simple walls and roof doors and window made with Loop Cuts, Inset and extrudes.
After modelling I have textured Walls and roof with PBR-textures.

Totally this will be 12500 verts times 9 - over 100 000 verts, But without LOD-ing still the FPS is close to 60 over this area.

Is it worth the work to use LOD-s in this case. I guess it isn't ? Also when I began with LOD1 and cannot get rid of more the 2000 verts / house.

Give me some advice if you have any...

// Erland
 
The difference is imemory used when using LODs. 60 fps is max I believe; will not go higher.
 
Many of Asobo's default buildings only use 1 LOD. I would think your use of them is fine.
 
I find it very satisfying reducing something to a tiny size that still looks the same from a distance.

Other than that, LODs can have uses beyond purely conserving resources.

For example with water masks having LODs that are set higher above the ground than the prime one stops Z fighting, and if you want something visible for many miles then multiple LODs of increasing size can help with that.

Making another LOD is usually very little work, it doesn't matter how ragged it looks after being decimated, so I often add one or two as long as they're small enough in kb.

Almost any texture can be reduced to 64x64 and still look reasonable as long as it's far enough away, apart from emissive stuff, so making an item negligible from afar shouldn't add much to download size.

I tend to do it more for things that will be repeatedly placed such as vehicles. That can add up rapidly.

Having said that I've never added enough of anything to ever slow the performance of an area.
 
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The recommendations for using LODs are set out by Asobo in the SDK:

LODs

docs.flightsimulator.com docs.flightsimulator.com

Keep in mind that while your computer may be able to handle the scenery someone using an XBOX might not. Also, when every developer decides not to use LODs and users start adding different scenery packages into the same area then you start to get problems.

I recommend that you play with the LOD debug window in MSFS. This is a very useful tool that can help you see exactly when LODs come into effect.

At the bare minimum (ie for small airports and scenery) I think you should have at least two LODs. A close up one and a far one. The far LODs should be as low detail as possible (simple boxes really with no textures). The reason you have the far LODs is to prevent your scenery stressing the system when it's barely visible. The total number of triangles in a small airport or scenery probably doesn't warrant a full set of LODs but you really should try to avoid having the sim draw 100,000 triangles (and loading a whole bunch of textures) when the user is 10NM away from your scenery.

Full multiple LODs should be used for something like a major airport which covers many miles.
 
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