Hi ycarry,

> because use of Catmull–Clark subdivision surface generate
> QUADrilaterals
> (from triangles or NGons or... quads)

That's true, but that doesn't mean it magically forms nice quads out of any kind of n-gon.

Part of the Catmull-Clark subdivision process involves connecting pieces to the centroid of the polygon. If you have a complex n-gon that is non-convex like the top face of the example I posted above, it will make for a messy folded-over-itself result.

That's basically why you can't use the kind of n-gon mesh that MoI generates as the input to sub-d smoothing - sub-d smoothing requires a particular kind of topology to the inputs to it in order to produce good results, and that topology is best built by hand.

But you don't need to apply sub-d smoothing to MoI generated meshes anyway - MoI exports vertex normals to make the shaded result already look nice and smooth, you just directly render the mesh that MoI exports and you shouldn't try to apply sub-d smoothing to it.

- Michael

Hi Felix,

> From the little I know, quads seems to work better
> with the Catmull-Clark sub-d method.

It's not just simply having quads - to get good subdivision results also requires a suitable topology.

There are all kinds of bumps and wrinkles and artifacts that can be caused by poorly suited topology being used for sub-d, see this video for a good overview of that:
http://vimeo.com/2158706

That video covers a variety of sub-d smoothing artifacts, and how to best arrange your input mesh structure to avoid them.

If you want to produce sub-d smoothing, your best bet is to create the mesh for it by hand, following a strategy that produces a good sub-d friendly topology. It's a whole different modeling process than building stuff in MoI and exporting an n-gon mesh.

- Michael

Thanks for the video link Michael,

I saw it before but it's still quite interesting. Also, thanks as well for all the info you gave on quads as well.

Regards,
Felix