D3DXCleanMesh claims to duplicate vertices where "bowties" exist. However I notice that for pretty much any mesh I try it won't fix any of the bowties at all and if I am lucky it might remove one or two. Is there reason why it fixes some bowties but not others? I notice that the D3DXMesh functions detect bowties whenever I index my geometry which would be expected as this inherently causes vertex sharing which seems to be the source of the problem. Anyways, it is an annoyance since D3DXComputeTangentFrame will not produce any results for a mesh with bowties detected in it and pretty much limits what would otherwise be a very powerful and useful function. So far I've been able to get good results on a box, sphere, and cylinder mesh with no bowties but anything more complex will be broken.