i3d with residues / marching cubes

[TheDunadan]

Hi,

does anyone know if there have been any attempts in adding residues to the voxel support in Houdini. Rather accidently I found out that our university spends a good amount of time on developing VCM (virtual clay modeling) systems. They use a a voxel based representation here, but since they actually need some tools to get finally a nurbs surface object back they couldn't life with this blocky 'structure' of simple voxel representation, but use residues to get smoother results.

I think the image above makes quite obvious what I'm talking about. They aren't good for everything, but they'd allow a much cleaner voxelrepresentation of geometry and in conjunction with something such as a CFD system or alike it might be good for some nice tricks, can't tell for sure, but I think our fluid dynamics department has a cfd sim that uses residues already (since it has a scientific purpose it's rather slow and wouldn't be enjoyable for any 3d works).

As mentioned above: we can get a nice surface representation back and the algorithm here involved is very simple. This might be for quite useful as well most of the time.

Has anyone done something similar with i3d and Houdini so far or intends to? Unless there are any patent related problems I might be tempted to try adding a conversion tool for Houdini, even if it's only good to use volumetric shaders on geometry.

Jens

[edward]

I think what you're talking about are the signed distance fields used in the level set methods? I recall that was mentioned recently here ... try searching for level set.

[TheDunadan]

I think what you're talking about are the signed distance fields used in the level set methods? I recall that was mentioned recently here ... try searching for level set.

15142[/snapback]

Gotta do some further reading now... possibly it's the same and they labled things differently. Here in a bit more detail what their approach is about and what for:

The point of the system I had a look at, is that it supposedly allows to replace those real clay models that are still widely used in the industry for prototypes of design with digital ones--> They work on Virtual Clay modelers. Here at the uni they do all sorts of other fancy additions to make this virtual clay modeling as realisistic as possible (e.g. cave '3d hologram', force feedback controls to 'touch/feel' the surfaces, and many other gadgets to make things even more intuitive and nicer for the designers). The part the industry is most intrested in, is to convert those models afterwards directly into NURBS surfaces to avoid the otherwise very time consuming process of makeing a 3d laser scan + rebuilding the sufaces. Besides voxel representations allow some very intresting simulations that FEM methods cannot deal with properly. Some even suggest that whole CAD modeling systems will use 'voxelesque' datastructeres for the internal geometry representation in the near future.

Anyhow, they spent a fair deal of time on how to represent geometry in a voxel like structure since they need such kinda representation for the modeling system to work efficiently. The current datastructure is quite complex and it's a hybrid 'voxel-octree-and-more' thingy. However the first methods they used were fairly simpel and ensured that rather quickily the voxel data could be converted into a nice closed surface mesh. They used 3 vectors on each side of the 'voxel sides' to allow a well defined interpolation for the surface mesh (this is the part that sounds like signed distance fields thing you're talking about. They called these residues however and the simplest conversion alorithm 'marching cubes' (both seem quite common in medical surface/ volume reconstruction).

If with the upcoming level sets in Houdini feature this and possibly more, there won't be a need for this crude thingy

Bedies, having had a look or two at the sidefx/journal my main point of intrest in Houdini isn't that big anymore If metamarch() and ScatterMeta OP do what I think they'll do, I can't wait for a new apprentice edition version of Houdini to be released soon.

A very sleepy Jens