.

Developer

C++, .NET

Summary

Demonstrates how to see if a planar surface lies in a specific plane.

Question

How can I test to test if a planar surface lies in a specific plane?

Answer

Unlike curve objects, which implement the ON_Curve::IsInPlane virtual function, there is no function on ON_Surface derive objects that will test for this situation. But, if you obtain the corners of the surface object, you can test to see if they are within a specified tolerance of test plane. The following example code demonstrates how to do this.

C++

  static bool IsSurfaceInPlane( 
          const ON_Surface& srf, 
          const ON_Plane& plane, 
          double tolerance = ON_ZERO_TOLERANCE 
          )
  {
    // Is the surface planar?
    ON_Plane srf_plane;
    if( !srf.IsPlanar(&srf_plane, tolerance) )
      return false;


    // Get the surface corner points and project them
    // onto the surface plane
    ON_BoundingBox bbox = srf.BoundingBox();
    ON_3dPoint corners[4];
    corners[0] = srf_plane.ClosestPointTo(bbox.Corner(0,0,0));
    corners[1] = srf_plane.ClosestPointTo(bbox.Corner(1,0,0));
    corners[2] = srf_plane.ClosestPointTo(bbox.Corner(1,1,0));
    corners[3] = srf_plane.ClosestPointTo(bbox.Corner(0,1,0));


    // See if the surface corner points are within
    // tolerance of the test plane.
    bool rc = true;
    int i;
    for( i = 0; rc && i < 4; i++ )
    {
      if( fabs(plane.DistanceTo(corners[i])) > tolerance )
        rc = false;
    }
    return rc;
  }

VB.NET (Rhino 4)

  Public Function IsSurfaceInPlane( _
          ByVal srf As OnSurface, _
          ByVal plane As OnPlane, _
          ByVal tolerance As Double) _
          As Boolean


    ' Is the surface planar?
    Dim srf_plane As New OnPlane
    If (srf.IsPlanar(srf_plane, tolerance) = False) Then
      Return False
    End If


    ' Get the surface corner points and project them
    ' onto the surface plane
    Dim bbox As OnBoundingBox = srf.BoundingBox()
    Dim corners(4) As On3dPoint
    corners(0) = srf_plane.ClosestPointTo(bbox.Corner(0, 0, 0))
    corners(1) = srf_plane.ClosestPointTo(bbox.Corner(1, 0, 0))
    corners(2) = srf_plane.ClosestPointTo(bbox.Corner(1, 1, 0))
    corners(3) = srf_plane.ClosestPointTo(bbox.Corner(0, 1, 0))


    ' See if the surface corner points are within
    ' tolerance of the test plane.
    Dim rc As Boolean = True
    For i As Integer = 0 To 3
      If (Math.Abs(plane.DistanceTo(corners(i))) > tolerance) Then
        rc = False
      End If
    Next
    Return rc


  End Function

C# (Rhino 4)

  public bool IsSurfaceInPlane(
          OnSurface srf, 
          OnPlane plane, 
          double tolerance
          )
  {
    // Is the surface planar?
    OnPlane srf_plane = new OnPlane();
    if (!srf.IsPlanar(srf_plane, tolerance))
      return false;


    // Get the surface corner points and project them
    // onto the surface plane
    OnBoundingBox bbox = srf.BoundingBox();
    On3dPoint[] corners = new On3dPoint[4];
    corners[0] = srf_plane.ClosestPointTo(bbox.Corner(0, 0, 0));
    corners[1] = srf_plane.ClosestPointTo(bbox.Corner(1, 0, 0));
    corners[2] = srf_plane.ClosestPointTo(bbox.Corner(1, 1, 0));
    corners[3] = srf_plane.ClosestPointTo(bbox.Corner(0, 1, 0));


    // See if the surface corner points are within
    // tolerance of the test plane.
    bool rc = true;
    for (int i = 0; rc && i < 4; i++)
    {
       if (Math.Abs(plane.DistanceTo(corners[i])) > tolerance)
        rc = false;
    }
    return rc;
  }