Confusion about LOD's and mapping

polygonfreak

I have heard that you don't want to have more then four LOD's in your model but what does this mean? I can only have four uv maps/material ID's per model? And how does this apply to a large scenes? I am still some what new to modeling and UDK so any information would be such a great help. Thanks.

Froyok

In UDK, LOD are model which have fewer polygons than the original, but they have their personnal uv set. You can't set different materials, its automatically inherited from the first model.
4 is the maximum numebr of LOD you can have, so : original mesh + lod1 +lod2 + lod3 + lod4
First you import your model, then in the model viewer you import your LOD one by one. After that, you set the distance for the transitions between one or more lods in the models viewer.

See : http://udn.epicgames.com/Three/StaticMeshEditorUserGuide.html#LODs

gamedev

Hey there. In most cases, when you speak of an LOD, you are referring to Level Of Detail, or in most games, lower resolution / low polycount meshes that can be used to swap out for the original, higher res meshes when the player / camera get far enough away.

Maybe your actually talking bout the material slots in the UDK static mesh view window, that are labeled LDO[0] through x? In that case, then yes, multiple materials for a single mesh can be bad. The more materials a mesh has the more draw calls and slower performance for a level. You should try and keep most of meshes down to one material, two at most.

For large environments, this means breaking up meshes in a modular way, using tileable textures etc. For example, if you have a object that you feel needs multiple materials, can it maybe be broken down in a few meshes, each with one material instead?

There are always trade offs however, as too many meshes in a level has it's costs too.

hope that helps!

polygonfreak

First off, thanks to the both of you for taking the time to answer my question. And I am glad I asked this question, as I just imported a mesh, then created a low detail mesh, and created a LOD from that low poly model... I understand that finally, which only brings up one last question, what is the best method for having two or more uv maps to one large mesh? Or is this just a sloppy practice?