C# Point in Closed Mesh, Mesh Inclusion

Replies to This Discussion

Permalink Reply by John Abowd on November 4, 2014 at 3:03pm

Here's the code if too lazy to open file.

private void RunScript(List<Mesh> meshes, List<Point3d> points, ref object A)
{
List<bool> cullList = new List<bool>();

for(int i = 0; i < meshes.Count; i++)
{
bool inside = false;
foreach(Point3d pt in points)
{

if(meshes[i].IsPointInside(pt, 0.1, true) == true)
{
inside = true;
}
}

cullList.Add(inside);
}

A = cullList;

Permalink Reply by Vicente Soler on November 4, 2014 at 3:11pm

Can you simplify the definition so you don't need third party plugins?

Internalize data for everything except that part that is not working properly. If the file becomes very large, include only a subset of the geometry that still contains the error.

Permalink Reply by John Abowd on November 4, 2014 at 3:28pm

Sure, here is internalized points meshes. Morphed Cell Meshes is what I want to cull from, and Standard Cell Meshes is what I want to test for inclusion. But it currently only somewhat works when I test for the same set of meshes that I cull.

Attachments:

• cellular 3d morph attempt (2).gh, 1.7 MB

Permalink Reply by Vicente Soler on November 4, 2014 at 5:26pm

There seems to be a bug in the IsPointInside method.

I'm going to try to guess what is happening (It's likely I'm completely wrong):

This method gets the diagonal vector of the bounding box of the mesh and shoots a ray from the point in that direction. If the number of times the ray intersects with the mesh is odd, the point is inside.

In your case the point seems to be in the exact middle of the box and the mesh shape is the same as it's bounding box, meaning it intersects in exactly a corner. I guess this special case of intersecting exactly in a corner or edge might sometimes return an undesired number of intersections.

If you wiggle the points a bit you'll see it will work properly. Move them in two different axis so that the rays don't intersect on the edges.

In this particular case, though, you can just get the bounding box of each mesh and use the Contains method.

Permalink Reply by John Abowd on November 4, 2014 at 6:48pm

Your theory is interesting and had me temporarily excited. But I moved the points in the z and x directions and I got another different but still not correct result. I got practically no result when I used the bounding box and used Point in Brep, unless I misinterpreted what you meant by 'contains method.'

Permalink Reply by Vicente Soler on November 5, 2014 at 1:46am

This is how I got it working.

You can call the Contains method from a scripting component, I don't think there is an equivalent Grasshopper component.

Something like:

bool isInside = mesh.GetBoundingBox().Contains(point);

Permalink Reply by John Abowd on November 5, 2014 at 7:04pm

Wonderful. Thank you, sir.

Permalink Reply by Arend on November 5, 2014 at 11:48pm

I've created a plugin that can ease up this usage. It only works for orthogonal grids, but it does not require any intersection. Its internal representation is a list of bits (storage is quite low, compared to mesh boxes). The output is a voxelgrid that can be converted to a closed mesh. (only the outer faces are shown). If your input is points it works pretty well.

See also this thread: http://www.grasshopper3d.com/forum/topics/mesh-bounding-box-clash-d...

Attachments:

• example-voxelgrid.gh, 311 KB
• VoxelTools.gha, 173 KB