Mesh from closed polylines

[pearswj]

Create a mesh from a number of closed polylines.

A mesh from a closed polyline is straightforward:

1. Add polyline vertices to mesh
2. add a face with vertex indices 1...n where n is the number of vertices.

Creating a mesh from several polylines could be done in the same way with a secondary procedure to merge duplicate vertices. Duplicates could be merged either before (faster) or after (more flexible) the faces are added.

[pearswj]

Starling's pmDecompose component works pretty well for the purpose of creating a Plankton mesh from several polylines. Perhaps we should add a simple component that wraps up the code below?

# V: list of Point3d
# F: tree of int

import clr
clr.AddReferenceToFile("Plankton.dll")

import Plankton

pmesh = Plankton.PlanktonMesh()

for pt in V:
    pmesh.Vertices.Add(pt.X, pt.Y, pt.Z)

for face in F.Branches:
    face = list(face)[:-1] # see comment below
    pmesh.Faces.AddFace(face)

[pearswj]

Actually there's a bug in the Starling component. It counts all the vertices in a closed polyline (where the first vertex appears again at the end).

[harrilewis]

I'm doing some rough and ready plankton.

Is there a function to merge vertices within a tolerance?

[pearswj]

Not currently. The above definition using Starling was the best solution I've achieved so far.

[danhambleton]

Provided the vertices are exactly coincident, I've been using:

        PlanktonMesh PMeshFromPolylines(List<Polyline> faces)
        {
            var pMesh = new PlanktonMesh();
            //add n-gon faces
            var verts = new List<Point3d>();
            for (int i = 0; i < faces.Count; i++)
            {
                var currFace = new List<int>();

                for (int j = 0; j < faces[i].Count - 1; j++)
                {
                    var currPt = faces[i].PointAt(j);
                    var id = verts.IndexOf(currPt);
                    if (id < 0)
                    {
                        //push a vertex to list
                        //push that index to current face
                        pMesh.Vertices.Add(currPt.X, currPt.Y, currPt.Z);
                        verts.Add(currPt);
                        currFace.Add(pMesh.Vertices.Count - 1);
                    }
                    else
                    {
                        //push this index to current face
                        currFace.Add(id);
                    }
                }

                pMesh.Faces.AddFace(currFace);
            }

            return pMesh;
        }

And to convert a PlanktonMesh to polylines:

        List<Polyline> PolylinesFromPMesh(PlanktonMesh pMesh)
        {

            var faces = new List<Polyline>();
            for (int i = 0; i < pMesh.Faces.Count; i++)
            {
                var tmpCurve = new Polyline();
                var faceCirculator = pMesh.Halfedges.GetFaceCirculator(pMesh.Faces[i].FirstHalfedge);
                foreach (var id in faceCirculator)
                {
                    var idx = pMesh.Halfedges[id].StartVertex;
                    var tmpPt = new Point3d(pMesh.Vertices[idx].X, pMesh.Vertices[idx].Y, pMesh.Vertices[idx].Z);
                    tmpCurve.Add(tmpPt);
                }

                //close the curve
                tmpCurve.Add(tmpCurve.PointAt(0));
                faces.Add(tmpCurve);
            }

            return faces;
        }

[danhambleton]

Just found the ToPolyline method....I guess that works too ;)

[mikeheiss]

Hi @pearswj, I attempted to duplicate your example using GhPython, but I got the error "Data conversion failed from Goo to PlanktonMesh" on the output. Any ideas? Within the Python window I can print pmesh.Vertices[0].X for example and it works fine.

After I get this quad example working, I would like to attempt with ngon faces >4 sides.

[pearswj]

Hey @viper4049, I just tried this again in Rhino 5, Rhino WIP and Rhino WIP for Mac. Only in Rhino WIP for Windows do I see your error. I'll pass this on to @piac as he's responsible for the new Python script component in Grasshopper 1.0.

[pearswj]

@viper4049, I've moved this particular issue to youtrack.