Need Help with Multires

Hi everyone. Quick background info first. I’m making meshes for import into Second Life. Multires is a very important tool for this application, as it’s used to show how the model will deal with lower levels of detail when a user zooms out.

For this reason, it’s generally common practice to work with a mesh at 1/4 of it’s final resolution, so that when users zoom out, the key vertices defining the shape remain in place, and things don’t distort.

I need a little help with multires in general, though. It seems to be lacking for what I want to do. The scripts I use for generating SL compatible meshes, start off with the mesh at 1/4 resolution, and 3 multires levels. Allowing multires to be used to preview it at various detail levels. I’m trying to work at the lowest detail level, but the mesh keeps shifting around. Generally, if I position vertices at the lowest level, I’d expect the extra ones to appear in neat inbetween places when I increase the detail level, but this doesn’t seem to happen. I can sort of work around this by deleting and re-adding the multires, but this solution isn’t particularly great.

Is there any way to lock the lowest level vertices in place when going up multires levels, so that they don’t shift around? Or does anyone have some general advice/tips on using the multires function in general ?

You use Multires for LODs?! That doesn’t make any sense. Generally, something akin to Blender’s Decimate would be used to create lower LODs (or alternatively, an intern), but nobody ever ‘works his way up’ when building a model. Have you ever seen Half-life 2’s LODs? They’re automatically generated and look terrible, but you don’t even notice at that distance.

This isn’t even remotely what Multires is supposed to do (or can do).

You misunderstand. We don’t, and cannot generate LODs. SL does that automatically. Multires is just used to preview them, since the way the LODs are generated is a known constant. The blender sculpt scripts generate deformable shapes, with pre-done uvmapping and 3 multires levels, so creating a suclpt map from it is fairly simple.

Sculpt maps work as a 32x32 grid, with poles. deformed into the desired shape, and mapped out into a flat texture, using color channels as vertex coordinates. Multires works pretty well for them, as SL’s LOD basically just uses every second pixel at the first LOD level. then every fourth at the next, etc.

And yes, I know this is a bad/inefficient solution compared to actual meshes. Sadly, must work with the tools we have.

On the multi-res tab, instead of Catmul-Clark, use Simple Subdiv.
I think that will do what you’re hoping.