how do you make LOD models?

boyluya · Jul 2010

Hey guys, how do you usually make the LOD model of an asset? Thanks.

cholden · Jul 2010

Depends on the model really, but...

Delete as many non-silhouette or deformation importance edge loops until set percentage reduction has been reached. Remove unseen-at-distance faces.

Sometimes you have to consider normal and/or UV seams. Sometimes when reaching those super-low final steps it's worth the time to bang out a quick mesh so there's less clean-up.

boyluya · Jul 2010

So basically I just have to delete some edges? Wouldn't that affect the mesh normals?

CheeseOnToast · Jul 2010

It does a bit, but this is alleviated somewhat by the viewing distance. Collapsing edge rings helps preserve an average of the sillhouette usually, so try to do that before deleting loops and stray edges.

boyluya · Jul 2010

Ok cool, thanks guys!

EarthQuake · Jul 2010

Sometimes it will be important to re-bake normals for your lods.

ZacD · Jul 2010

Its also smart to make the model a constant black and compare the silhouettes of the LOD's and the original, you don't want any major poping.

PhilipK · Jul 2010

I find keeping the smoothing as intact as possible is almost equally (or more) important to keeping the outer silhouettes. Of course, if you make sure the silhouettes are intact you often get a similar smoothing result, unless your model have huge smoothed surfaces that are counteracted by the normal map, so if you were to remove any of that geometry you'd end up with a concave surface. This depends heavily on what type of engine you use and how much the smoothing affects the surface really. But it can pop really horribly if you're unlucky.

Planning for additional lod steps can be good early on. That way you may be able to avoid running into such problems (from my own experience that can be REALLY annoying to fix afterwards, especially if it's a huge set of meshes :S)

r_fletch_r · Jul 2010

EQ: is it possible to manually shoehorn those new normal map bakes into the existing textures Mips?

Neox · Jul 2010

if your engine can read dds, yeah should be possible i guess, question is are mips really bound to lod levels or are they independent from each other?

Ruz · Jul 2010

be careful though in max if you are collapsing edge loops as the edit poly can mess it up and you get corruption which you cannot undo.

Neox · Jul 2010

which max version are you using? i can't remember ever having this issue :O

Tumerboy · Jul 2010

Ditto. It'll fuck up UVs if you collapse an edge that is also a UV shell edge. . . but I've never gotten a corrupted file from it?

[HP] · Jul 2010

There's not a lot to it really, just keep on shitf+backspace on those unnecessary edge loops, and try to keep your silhouette as intact as possible.

Ruz · Jul 2010

Neox, it was a big issue in max 8 , not sure if it has been fixed yet.
Only seemed to happen if you had an edit poly on the stack and did an undo. so you might spend an hour optimizing a hairstyle, then hit an undo and gets verts everywhere. real pain and it didn't 'always' happen

how do you make LOD models?

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