For movie15-based 3D embeds, how to get u3d files?

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I posted the following question over at tex.stackexchange but as a newbie there, I can only post one link, so I put a linked version here.

The movie15 package requires 3D files to be in u3d format for embedding into pdf. This works fine with the sample files provided, and I have no problem generating suitable 3D files, but so far, I have not found a way to convert them to u3d. MeshLab, usually the first place to go for such things, crashes during u3d export.