Grasshopper

algorithmic modeling for Rhino

Hey, thanks for reading.

I am trying to mesh a closed brep volume with tetrahedrons, for the purpose of finite element analysis.

Two options I thought of were,

1) meshing it in Grasshopper. Though I can't find a plugin that does it. Meshedit says it offers volume meshing but I can't seem to find the component that does that.

2) meshing it outside with for example gmsh. Problem is, once I export it (as iges, or step) the geometry is interpreted as a polysurface, and not a solid. So 2D meshing works but there is no actual volume.

Anyone else had the same issue? or have solutions for it?

Thanks a bunch,

Tim

Views: 3616

Replies to This Discussion

Sorry for bumping my own post.

I managed to mesh the geometries externally with Gmsh (through a cmd call in rhino python). Though I am still at a loss for finding a component that meshes 3d breps within grasshopper.

I am looking for a "simply" Delaunay triangulation that goes from the surface mesh into the 3d mesh.

Any ideas would be greatly appreciated.

Tim

Hi Tim.

Such grasshopper component does not exist, at least not currently. It would have to be custom written.
What you have read about Mesh Edit is that it offers mesh volume analysis (meaning: calculating mesh volume and mesh centroid) not 3d meshing.

Thanks for clearing that up! Also good to know that it doesn't exist.

any example of what you need? Is it similar to a convex hull?

An example from Gmsh is shown here.

The result should include a list of nodal id, and corresponding coordinates, and a second list including all the tetrahedron elements, with the corresponding nodal id.

From what I could do within grasshopper, the closest thing I found was to populate a brep with points, and use voronoi 3d. But then, the resulting cells aren't necessarily tetrahedrons. There isn't a "split" component available..to my knowledge either.

Hi Tim,

Im also searching a way to make a 3d delaunay mesh (volumetric mesh). Did you find a solution?

I tried something by making a structure by using the voronoi 3D centroids and faces, if you want to have a look.

Sorry, haven't been active on here for a while.

I tried that as well. Delaunay is great for making a truss structure though the bounding box are by definition not "filled". Voronoi fills the bounding box but isn't a truss (no tetrahedrons), I fixed that by connecting each voronoi cell's vertices to its centroid. It works, but the resulting elements may be sliver-like.

You can export the surface mesh as an STL file and providing the mesh is ok ie no high aspect ratio elements, you can import it into a free program called LS Prepost from the www.lstc.com website.  This allows you to generate a tet mesh subject to the above criterion.  If you need some help with this software, I can give you some help.

I also recently ported free Tetgen to Grasshopper:

http://www.grasshopper3d.com/forum/topics/shortest-walk-tapered-bra...

RSS

About

Translate

Search

Photos

  • Add Photos
  • View All

Videos

  • Add Videos
  • View All

© 2024   Created by Scott Davidson.   Powered by

Badges  |  Report an Issue  |  Terms of Service