Creating LoDs

The_Kozmonaut

My biggest question is how does the lowest detail object have the same UVs as the main object? Do you lay out UVs on the original and then duplicate the object and remove edge loops etc to create the next LOD and so on? This may be pretty simple but I just have no experience in creating them.

Tumerboy

Well, it does and it doesn't. . . there's probably no tutorials, because it's a fairly simple thing. You either make another, lower poly mesh, and then UV THAT one as well, to use the same maps as closely as you can.

Or, you take your original model, and keep removing edges until you get something around the poly count you want, and then you fix any UVs that got screwed up in the process.

The_Kozmonaut

Thanks. Yea you are right I really dont need a tutorial I guess my question was all I needed to know. At first I was thinking it was transfered UVs or something like that so I just couldnt figure it out. Which method is most commonly used? I guess it probably is case specific depending on the mesh.

Well either way, I can just try both. I figure I will do the first option and just try and match the UV's as close as possible

Mark Dygert

Nothing really beats reducing polys by hand in any app. But there are some pretty good plug-ins available that do a pretty good job of reducing polys. I'm not sure what 3D app you're using but there is one for 3dsMax called PolyCruncher that does a pretty good job at not messing up your UV's, but can mess up the topology and it costs, so I've never found a use for it.

http://www.mootools.com/plugins/us/polygoncruncher/index.asp

I think you should keep in mind that there are several ways to do the same operations and some of them help preserve your UV's. For example;
- If you need to fill in a hole, try using bridge or cap. Creating a poly or extruding an edge will create problematic UV's.
- Try removing verts/edges instead of welding them.
- In the UV editor using relax with "hold boundry points" turned on helps you keep the UV island edges intact while allowing problem UV's to surface, making them easier to fix if edges are broken or in need of being rewelded.
- If you do need to weld verts make sure that preserve UV's is turned on, and if it distorts the UV's when you weld try target welding the verts in reverse order, a tricky operation but sometimes works.

There are other tips and tricks but I'm not sure if I should get into them because I'm not even sure what 3D app you're using...

Ruz

hmm I seem to be turning in to the lod master:) yeah best way is to use collapse edge and also target weld with preserve uv's turned on.

so yeah select a ring and collapse edge or select a loop and remove edge with ctrl , then you lose the verts as well.

The_Kozmonaut

Okay so now my problem is...When I remove an edge the diffuse UV's in channel 1 are okay, but the UV's in channel 3, for the light map, jump to a new location. It seems like a bug because even if I undo the UVs stay in the new spot that they jumped to. They aren't distorted or anything they just jump to what seems to be a random spot. I am using Max 2008. Any ideas?

btw, I have preserve UVs turned on and it shows 1 and 3 as yellow buttons.

leilei

Vig wrote: »

Nothing really beats reducing polys by hand in any app.

this is true. Nice control of shape and you don't funk your UVs if you just collapse the edges that aren't the edge of the UVs.