Level Designers: Dealing with LODs Thread - Survivor: Eye of the Storm

LOD or Level Of Detail.

If you have to import models into UDK you will also have to deal with the LOD chain. Setting up the LODs is a simple process but I thought I better write a quick guide for anybody who might need help on the method.

So you are importing a building/prop into UDK, the 3D artist has uploaded the model to sugarsync and inside the models folder is 4 .ase files named Survivor_Dumpster.ase, Survivor_Dumpster_LOD1.ase, Survivor_Dumpster_LOD2.ase and Survivor_Dumpster_LOD3.ase

Survivor_Dumpster.ase is the full detail model, this model you need to import to UDK via the generic browser (you should know how to do this)

Survivor_Dumpster_LOD1.ase, Survivor_Dumpster_LOD2.ase and Survivor_Dumpster_LOD3.ase. Theses are the LODs to import these you will need to open up the model viewer for Survivor_Dumpster.ase you can do this by double clicking it in the generic browser. Once the viewer is open you need to click Mesh > Import Mesh LOD...> (this is in the top left of the model veiwer) Locate Survivor_Dumpster_LOD1.ase and open it a new dialogue box will pop up with a drop down, make sure ADD NEW is selected and click ok. Repeat this for all the LOD models (make sure you choose ADD NEW for each new LOD model)

Thats the LODs impoorted and they will now work but you might want to play with a value that will alter the distance that the LODs swap.
To do this, while still in the model viewer the right hand menu of option you will need to find LODDistance Ratio its the 4th option in the BODY SETUP category. The higher you set the ratio the further away the lod models will swap.

You as the level designer will take responcibility for the LOD Ratio. Two things to take into account while settiing the ratio.

1. How BIG is the model.

Large models such as a full building you will need to make the raio lower, buildings can be seen in the distance and you want the player to be able to look at the skyline without it effecting FPS

2. How much detail is lost between LODS.

If the High detail model for the building is 20,000 polys and LOD1 is 14,500 you will probably get quite a bit of detail lost in the swap you dont want the player to notice this stuff you just want the player to see a building and not notice the pipes are missing or that the doors are now flat with a texture. so you need the model to swap out a bit further away and set the Ratio higer.

Now in both of those examples I used a building which is large and the swap would be quite drastic so I would set the LOD Ratio to about 1.2. If for example the model was a 100 poly bottle you could set that distance really high as the player will probably not notice the change and will only see the full detail model when right up close.

I think thats about everything you need to know if anything else comes up then i will add it

great post, very informative