OSD Bilinear subdivision

cwichura

Anyone got a link to a clear description of how bilinear subdivision approaches a mesh? My Googlefu is clearly not up to snuff on this one.

I ask because bilinear seems to be the only OSD algo that lets many low-resolution props keep their proper shape without having to explicitly set vertex and edge weights (of which the UI in Studio 4.6 is so primitive, it's basically unusable in my attempts at poking around with this in the PGE). I'd like to understand why Bilinear is keeping the shapes of props made with lots of large, single quads for walls and the like.

Upon closer examination in wireframe view, I'm not sure Bilinear actually helps in curves, however. A low-poly cylinder still looks like a low-poly cylinder, just with the faces split up. No rounding has occurred to smooth out the curve of the cylinder. The problem, of course, is that these low-poly props are all one big object, so you can't selectively apply subdivision to just the curved surfaces as it pulls the wall apart when you select any of the other algos.

Thanks

prixat

If you look up the differences between Bezier and B-spline, you'll get the information you're after.

Bilinear (or Bicubic) is the 'B' in B-spline.

Its essentially the same algorithm used in 'smoothing'. The limit surface goes through the existing vertices and all you get are slightly softened edges but no drastic changes in shape.

Catmark and Catmul-Clark use Bezier interpolation, the limit surface hardly ever goes through the original vertices and shapes are drastically rounded.

The best place to use the setting is on a mesh that was not created for classic subdivision but where you still need the extra polys.