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.
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.
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)
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
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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.
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)
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