subdivision surfaces

[Taylor Holliday]

Does anyone know of an easy to use C/C++ open source library for rendering subdivision surfaces efficiently (e.g. Stam's SIGGRAPH 98 paper) w/o a GPU?

If I can't find one, I'm considering writing a library with a GLU-ish C interface, something like: sds.h

thoughts? (thanks!)

[Brolingstanz]

Have you tried a google for Catmull-Clark/Loop subdivision? I know there's a bunch of code out there, if that's what you're looking for.

[Mikkel Gjoel]

source:
http://www.multires.caltech.edu/software/fastsubd/
http://mrl.nyu.edu/~biermann/subdivision/
http://www.subdivision.org/subdivision/demos/index.jsp

Cheers,

[Taylor Holliday]

Hi, yeah I've googled around quite a bit. Most of the code people have posted does explicit subdivision, which is too slow for my purposes (interactive modeling).

There is an implementation for this paper: http://www.multires.caltech.edu/pubs/fastsubd.pdf but it uses uniform sampling.

I've considered ripping an implementation from an existing subdivision modeler (blender, etc), but their implementations are tied to their respective architectures.

[Taylor Holliday]

Hi Mikkel, didn't see your post. I mentioned the first link above and the second two use explicit subdivision. Also, the second two don't have documented APIs.

[Taylor Holliday]

Just want to ensure I'm not re-inventing the wheel before I set out to write a nice SDS library. Would anyone like to see a lib with an api like GLU NURBS?

[Brolingstanz]

Most of the code people have posted does explicit subdivision, which is too slow for my purposes (interactive modeling).

Not sure what you mean here. Most if not all of the papers describing subdivision surfaces are presented in the context of interactive modelling. Even a fairly naive implementation of Catmull-Clark subdivision is adequate for many character modelling applications.

What'll be interesting to me is subdivision algorithms implemented on the GPU as geometry shaders become available in the coming year. There you'll have the ability to save lots of bandwidth by streaming a fairly simple control mesh and subdividing to arbitrary complexity on the GPU.

But I don't see why anyone would object to a subdivision library, in the finest tradition of the OpenGL API :-)

[Mikkel Gjoel]

Hi Taylor.

The "FastSubd"-implementation is immensely fast. It uses tables to accelerate the calculations. There is also a paper describing hardware-implementation using render-to-vertexarray functionality. I believe a similar method is used to implement the "turbosmooth"-modifier in 3dsmax.

One of the advantages of this method is that you can do single-triangle subdivision - ie. you do not need to calculate the entire mesh to view or re-view a subset of the mesh. This is ideal in regards to interactive modelling - all you need is local connectivity (1-ring) information for the area you wish to subdivide. Of course, you should render the entire mesh at the same subdivision level (or take care of the cracks otherwise), but you don't need to calculate the entire mesh when modifying locally.


Kind regards,

[Taylor Holliday]

Hi Leghorn, what I mean by explicit subdivision is that individual facets of finer meshes are dynamically allocated. I've implemented subd's this way and its pretty slow. An array-based implementation is faster.

best

[Taylor Holliday]

Here's a very early draft of a spec for the library I'm thinking of: http://wtholliday.org/software/src/sds.pdf

Any suggestions would be greatly appreciated. I'm thinking of starting a sourceforge project for it.

thanks!