marshaling points in RhinoCommon

gistfile1.cpp

// C++ portion
// Declare a struct that directly maps to an ON_3dPoint
struct ON_3DPOINT_STRUCT{ double val[3]; };

extern "C" __declspec(dllexport)
void ComputeMeshPoints(int resX, int resY, int resZ,
                       double* data_array, int data_count, double iso,
                       ON_3DPOINT_STRUCT min_corner, ON_3DPOINT_STRUCT max_corner,
                       ON_SimpleArray<ON_3dPoint>* output_points)
{
  if( data_array && output_points )
  {
    ON_3dPoint minCorner(min_corner.val);
    ON_3dPoint maxCorner(max_corner.val);
    // perform calculations and add points to output_points
  }
}

////////////////////////////////////////////////////////////////
// C# portion
using System;
using System.Runtime.InteropServices;
using Rhino.Geometry;

static class UnsafeNativeMethods
{
  [DllImport("my_c_library", CallingConvention=CallingConvention.Cdecl )]
  public static void ComputeMeshPoints(int resX, int resY, int resZ,
    double[] data_array, int data_count, double iso, Point3d min_corner,
    Point3d max_corner, IntPtr pPointArray);
}

static class MyFunctions
{
  // Use the pInvoke function in your function
  public static Point3d[] MyMeshPointsFunction(int resX, int resY, int resZ,
                                               double[] data, double iso,
                                               Point3d minCorner, Point3d maxCorner)
  {
    using( var pointArray = new Rhino.Runtime.InteropWrappers.SimpleArrayPoint3d() )
    {
      IntPtr pNativePointArray = pointArray.NonConstPointer();
      UnsafeNativeMethods.ComputeMeshPoints(resX, resY, resZ, data, data.Length,
        iso, minCorner, maxCorner, pNativePointArray);
      return pointArray.ToArray();
    }
  }
}