How can I impove this code? bounding box problem in C#

[zhuangjia777]

Hi

I am coding a C# script in grasshopper. My aim is to find the bouning box either has minimum volume or align with long axis of the object.

One of my issue: For searching the minimum volume, I set a very large number to compare with at first place. I feel there could be a better way. If someone can help, it will be very thankful.

I post the code and attach the file.
bounding box EX.gh (11.0 KB)

 private void RunScript(List<GeometryBase> geo, int n, int VorA, ref object A, ref object Box)
  {
    //make a list of planes for bounding box to align with.
    double angle = Math.PI / n;
    Plane myPlaneZ = Plane.WorldXY;
    List<Plane> myPlanesZ = new List<Plane>();
    List<Plane> myPlanesY = new List<Plane>();
    List<Plane> myPlanesX = new List<Plane>();

    //create a list of rotated planes align z axis.
    for (int i = 0; i < n; i++)
    {
      myPlaneZ.Rotate(angle, Vector3d.ZAxis, Point3d.Origin);
      myPlanesZ.Add(myPlaneZ);
    }

    //rotate each plane align y axis. Planes are structs. You need to get them out of the list (which creates a copy) modify the copy, then put it back into the list.
    for (int i = 0; i < myPlanesZ.Count; i++)
    {
      for (int j = 0; j < n; j++)
      {
        Plane p = myPlanesZ[i];
        p.Rotate(angle, Vector3d.YAxis, Point3d.Origin);
        myPlanesZ[i] = p;
        myPlanesY.Add(myPlanesZ[i]);
      }
    }

    //rotate each plane align x axis.
    for (int i = 0; i < myPlanesY.Count; i++)
    {
      for (int j = 0; j < n; j++)
      {
        Plane p = myPlanesY[i];
        p.Rotate(angle, Vector3d.XAxis, Point3d.Origin);
        myPlanesY[i] = p;
        myPlanesX.Add(myPlanesY[i]);
      }
    }

    //create index for searching.
    int index = 0;

    //search minimum volume and return index.
    if (VorA == 0)
    {
      double minVolume = 100000000000000000000.0;
      for (int i = 0; i < myPlanesX.Count; i++)
      {
        Plane p = myPlanesX[i];

        //union bounding box, for bounding each object use code "var bbox = geo.GetBoundingBox(p);"
        BoundingBox bboxUnion = BoundingBox.Empty;
        foreach (var obj in geo)
        {
          var bbox = obj.GetBoundingBox(p);
          bboxUnion.Union(bbox);
        }

        //get bounding box volume.
        var box = new Box(bboxUnion);
        double volume = box.Volume;

        //find the minimum.
        if (volume <= minVolume)
        {
          minVolume = volume;
          index = i;
        }
      }
      Print("Minimum Volume");
      A = minVolume;
    }

    //search longest axis and return index.
    if (VorA == 1)
    {
      double longestAxis = 0.0;
      for (int i = 0; i < myPlanesX.Count; i++)
      {
        Plane p = myPlanesX[i];

        //union bounding box, for bounding each obj use code "var bbox = geo.GetBoundingBox(p);"
        BoundingBox bboxUnion = BoundingBox.Empty;
        foreach (var obj in geo)
        {
          var bbox = obj.GetBoundingBox(p);
          bboxUnion.Union(bbox);
        }

        //get box width.
        var box = new Box(bboxUnion);
        double axis = box.X.Length;

        //find the longest.
        if (axis >= longestAxis)
        {
          longestAxis = axis;
          index = i;
        }
      }
      Print("Longest Axis");
      A = longestAxis;
    }

    //output bounding box.
    Plane plane0 = myPlanesX[index];
    BoundingBox bboxUnion0 = BoundingBox.Empty;
    foreach (var obj in geo)
    {
      var bbox = obj.GetBoundingBox(plane0);
      bboxUnion0.Union(bbox);
    }

    //transform the box to worldXY.
    var box0 = new Box(bboxUnion0);
    box0.Transform(Transform.PlaneToPlane(Plane.WorldXY, plane0));
    Box = box0;

  }

[siemen]

You can use double.MaxValue

Double.MaxValue Field (System)

[zhuangjia777]

double minVolume = 100000000000000000000.0;

can be written as

double minVolume = Double.MaxValue;

[zhuangjia777]

I got it. Thank you very much.

[inno]

I have done something like this a while ago using galapagos and classic GH components, used it for finding the best way to crate art pieces using the smallest amount of wood for the crates

maybe you could limit the angles to explore to 0.5 * Pi → 0.5 * Pi / n ?

I’m just thinking out loud here, if the starting condition is like the following, with the reference plane for the Bounding box ready to start turning counterclockwise:

once you reach the Pi/2 = 90° mark, X and Y sizes are the same as the initial condition, just inverted values, so (in my mind) half cycle might be calculating solutions that were already explored?

[zhuangjia777]

yes. you are right. Half of Pi is enough. Thank you.

[Joseph_Oster]

bounding box_2021Feb15a.gh (14.5 KB)