Hi all,

I've been playing around with Maya on and off for about six months, mainly with trying to get modeling together before moving on. However, on anything but the most simple model, I always seem to get to the same dead end.

From the early tutorials I read, then the convert poly / subdiv / poly as you go seems to be the best way of working. However, I always seem to get to a point where the poly model looks fine, but it will not convert to a subdiv. I get the 'use cleanup with the non-manifold option' message. When I do this, the model will then show a border edge around each of the faces. If I then select them and merge the vertices the border edges disappear. If you try to convert to subdivs, you get 'use cleanup...'. Rinse and repeat ad infinitum.

The techniques that I am trying to fix the poly geo:

Merging vertices (individually and with all of the vertices selected)
Cleanup (with the non-manifold option set)
Hunting down incorrect normals (show normals, backface culling etc)
Conforming the normals and reversing where they are incorrect
Using 'show border edges' to find any unexpected edges (merging etc)
Removing any additional faces and 'orphaned' edges.

So my questions are:
1, Am I missing any techniques for finding problems in the poly geo?
2, Is there any way of getting more information out of Maya on where the problems are (e.g. is there something that MEL could tell me)?
3, Is there such a thing as 'unfixable' geometry? If so, how can I avoid getting myself into that position?

Finally, this problem tends to occur after I start extruding faces and using split polygon. I _think_ I'm always careful to ensure that I'm splitting quads into more quads and that the split are logical. Is there something that I could be doing wrong at this stage?

I know that this is a topic that has been covered a hundred times on all of the forums and the techniques that I have learnt have come from scouring those posts. However, I still can't get round this! Any help would be greatly appreciated.

Cheers,
Ian