Volume from points in 3D Space (problem with invalid mesh)

[thomas_do]

Hey everybody,

I am trying to create a volume from a few points in 3Dspace. I tried to use the method I found here:

GH: POINT VOLUME

(You have to download Mesh Analysis and Utility Plug-In for the component cullVertices)

The mesh that is created looks good, just like I want it, but for some reason it is invalid so I cannot bake it.

I tried some tricks from the forum for invalid meshes (deconstruct mesh and reconstruct, explode mesh and rejoin) but it did not work.

In the end I want to use the volume as a boundary region in millipede, so it has to be a brep. Maybe there is also an easier way to get a brep from these points.

points_to_mesh.gh (11.5 KB)

[laurent_delrieu]

Hello
You could use Convex Hull from MeshEdit

MeshEdit

Alpha Shape

Alpha Shape 3D

Here is an implementation of 3D alpha shape, it is using 3D DelaunayCell (standard GH component ??). https://doc.cgal.org/latest/Alpha_shapes_3/index.html https://doc.cgal.org/latest/Alpha_shapes_2/index.html I liked a lot the explanation of Alpha Shape of CGAL site “Imagine a huge mass of ice-cream making up the space R3R3 and containing the points as “hard” chocolate pieces. Using one of these sphere-formed ice-cream spoons, we carve out all parts of the ice-cream block we can reach withou…

Smothed outer surface from a 3D set of points

Here the script with Alpha Shape 3d [image] There are some holes but you have a mesh. Parallel version of Alpha Shape is faster. point cloud alpha shape.gh (13.5 KB) There are windows !! I dn’t know if it is my script or Delaunay 3d (from Mesh Edit) [image]

[tim.stark]

Didn’t see you already answered and made him an example with your alpha shape

Anyways here it is:

points_to_mesh_re.gh (14.7 KB)

The reason why you got a invalid mesh is, that you created a sphere with 4600 faces.You pulled the verticies to the nearest point of 24. So you got an endless amount of faces and verticies, overlapping etc.

[thomas_do]

Thanks guys!

It works fine for me with the ConvexHull component.

With Alpha Shape I always get holes in my mesh, no matter which radius I use.

[tim.stark]

As you can de in my file, there are no holes.

Funny, as I made the example for you I also tried convex Hull, but got holes

[thomas_do]

Pretty sure there is a rectangular hole at the top (you can see that the area is a little darker in your image). At least that is where my hole was when I tried it out.

[Michael_Pryor (ekim)]

Please don’t rely on my 7 year old blog
Grasshopper and I have changed a lot since then.

[Michael_Pryor (ekim)]

However, I think the issue is a Rhino 6 one. Opened your file in R5 and works as expected. I think R6 has more conditions on what it considers Invalid. R5 had less restrictions (not such a good thing).

[laurent_delrieu]

@thomas_do

It works fine for me with the ConvexHull component.

The same here

@thomas_do

With Alpha Shape I always get holes in my mesh, no matter which radius I use.

I get the same thing also, my script has flaws. It is possible to fill that in Rhino with FillMeshHole

[tim.stark]

You’re right. Don‘t know how I couln‘t see that… should check always twice

[Michael_Pryor (ekim)]

I get the same thing also, my script has flaws. It is possible to fill that in Rhino with

You might add something like that in the script to cover the holes.

if (!M.IsClosed)
{
Polyline nakedBoundaries = M.GetNakedEdges();

  for (int i = 0; i < nakedBoundaries.Length; i++)
  {
    if (nakedBoundaries[i].IsClosed)
    {
      Mesh fillHole = Mesh.CreateFromClosedPolyline(nakedBoundaries[i]);
      M.Append(fillHole);
    }
  }
}

[laurent_delrieu]

Thanks Michael. This is really helpful, also for other script I have in mind.

[jarod]

Hi, I just started learning grasshopper 2 weeks ago and i ran into the same issue… just wondering is there any gh file that i can refer to (using Convex Hull component) after its been solved?

Thanks in advance!