Mesh Bounding Box Clash Detection

Replies to This Discussion

Permalink Reply by Arend on May 7, 2014 at 5:07am

The voxeltools support a geometry that is quite lightweight in terms of memory.  A voxelgrid is defined by it's bounds (a bounding box, can have a plane). The memory footprint of a voxelgrid is 1 bit per voxel + some overhead for the boundingbox, a grid can be converted to a mesh (there is some nice casting going on).

Right now I could not yet work with your example of the bunny, but it should be possible to adapt so it will work anyway. I'll try to wrap up an example tonight.

Permalink Reply by Arend on May 11, 2014 at 10:25am

A bit later than planned, but here they are. This is the latest version - which contains some in development features.

Attached in an example with a C# block that should contain an assembly linked to the attached gha. Right now it does not do completely what you're looking for (but I still have a bit of an A > B problem (For what A, is your mesh mesh intersection the solution).

I'll need to clean this up, add some documentation, and then I'll post the plugin at food4rhino.

Attachments:

• VoxelTools.gha, 169 KB
• meshbox-voxeltools.gh, 1.2 MB

Permalink Reply by Dieter Toews on May 19, 2014 at 1:15pm

Hey Arend,

I still have to look at your tools. I am building a GHA myself. If your tools end up being useful would it be ok to reference your code into my project (i'm not sure if you can load classes from a .gha directly but i know that they are just renamed .dll files)?

In the mean time i looked at the slow code i was writing and found this other"Search" overload in the rhino common sdk:

public static MeshClash[] Search( Mesh meshA, IEnumerablea href="http://4.rhino3d.com/5/rhinocommon/html/T_Rhino_Geometry_Mesh.htm">Mesh> setB, double distance, int maxEventCount )

Because the search generate a compacted list i had to do a bit of acrobatics but the resulting C# component is much faster.

private void RunScript(List<Mesh> testVoxel, Mesh testMesh, ref object A)
  {
    //do the clash detection on many voxels per mesh at once.
    Rhino.Geometry.Intersect.MeshClash[] clashresult = Rhino.Geometry.Intersect.MeshClash.Search(testMesh, testVoxel, 0.0001, 256);
    Print(clashresult.Length.ToString());

    //create some temporary storage containers
    List<Mesh> clashingVoxels = new List<Mesh>();
    List<int> results = new List<int>();

    //collect all of the voxel meshes that were found to have clashed.
    foreach (Rhino.Geometry.Intersect.MeshClash clasher in clashresult)
    {
      clashingVoxels.Add(clasher.MeshB);
    }

    //go though the list of all the voxels.
    //If a voxel appears in the list of clashing voxels(see above) then output 0.
    //If not the test if the voxel is inside or outside of the mesh.
    foreach (Mesh voxel in testVoxel)
    {
      if (clashingVoxels.Contains(voxel))
      {
        results.Add(0);
      }
      else
      {
        VolumeMassProperties voxelMassProp = VolumeMassProperties.Compute(voxel);
        if (testMesh.IsPointInside(voxelMassProp.Centroid, 0.00001, true))
        {
          results.Add(-1);
        }
        else
        {
          results.Add(1);
        }
      }
    }
    A = results;
  }

Permalink Reply by Dieter Toews on May 19, 2014 at 1:18pm

(speed note) - here I've done 9000 boxes in .4 seconds. The old version did 150 boxes in over 13 seconds. This is a ~1950x improvement! I suspect the problem likes in expensive object creation of my previous version vs an internal space partitioning algorithm being used in the background in this version. Since i want to roll my own (space partitioning) i may need to delve a little deeper.

Permalink Reply by Dieter Toews on May 24, 2014 at 3:31pm

Hi Arend,

I tried loading up your tools but and find them and your .gh file says that they are not there.

I've verified that your .gha is in my ~\AppData\Roaming\Grasshopper\Libraries\ folder...

Are you sure you included the right version?

Permalink Reply by Arend on May 24, 2014 at 6:08pm

Should be ok, did you also unblock the file? That's sometimes needed.

Permalink Reply by Dieter Toews on May 26, 2014 at 7:04pm

ok, I unblocked it but still had to manually enter the path:

when i manually add the path (as above) grasshopper freezes...

In the mean time i wrote a more complete version in visual Studio (see attached) - it's not quite finished as it doesn't convert it's output to a DataTree but it should produce the data structure I'm looking for for my bigger project...

Permalink Reply by Dieter Toews on May 26, 2014 at 11:00pm

i realized that have slightly old grasshopper - I'll update it tomorrow and see if it works after that :-)

Permalink Reply by Arend on June 12, 2014 at 10:52pm

Could you elaborate on your data structure (and why you need it, perhaps?)

Permalink Reply by Dieter Toews on July 9, 2014 at 3:52pm

In the bigger project the voxels are smart and communicate information between them. So this voxel class I've written will be extended with many other capabilities into a "Node" Class. The nodes communicate back a fourth between there near neighbors and also between there parents and children.

generally it will work like this:

step 1 - voxleise a model.

step 2 - set up topological relationships

step 3 - set up initial conditions

step 4 - simulate

step 5 - output.

Permalink Reply by dvdrbls on August 23, 2015 at 2:21pm

Hello Arend i love the voxel tools, is this the latest version?

Permalink Reply by Dieter Toews on May 30, 2014 at 3:52pm

Hi all,

Here is a compiling test version of the .gha i created for this... the output is a tree with a recusions of the voxels down to the one you specify.

It works but the performance is terrible (its same problem with the meshclash class as before because each child needs a new mesh clash object). I think if i go a bit lower level I can get a big performance boost. I'm thinking that the mesh face class will be something to look into as i try to roll my own mesh clash detector.

Attachments:

• mesh-box 5.gh, 1.5 MB

• ‹ Previous
• 1
• 2
• 3
• Next ›
• Page