How To: Add a Mesh Object to Rhino

Developer: C++, .NET
Summary: Demonstrates how to add a simple mesh object to Rhino.

To create an ON_Mesh:

1. Create the ON_Mesh object. The constructor requires the number of faces and vertices, and whether or not you have vertex normals or texture coordinates.
2. Fill in the mesh vertex array, ON_Mesh::m_V. You can also use ON_Mesh::SetVertex.
3. Fill in the mesh faces array, ON_Mesh::m_F. You can also use ON_Mesh::SetTriangle and ON_Mesh::SetQuad.
4. If you have vertex normals, fill in the normals array, ON_Mesh::m_N. You can also use ON_Mesh::SetVertexNormal.
5. If you have texture coordinates, fill in the texture coordinate array, ON_Mesh::m_T. You can also use ON_Mesh::SetTextureCoordinate.
6. If you did not specify vertex normals, have Rhino compute them for you using ON_Mesh::ComputeVertexNormals().
7. Clean up everything using ON_Mesh::Compact.

You are now ready to add this mesh object to the document. The opennurbs_mesh.h header file is well documented. It's worth reading through at least once.

CRhinoCommand::result CCommandTest::RunCommand( const CRhinoCommandContext& context )
{
  // Example demonstrates how to create a mesh and add it to Rhino
 
  // Create a mesh to write.
  // The mesh is a pyramid with 4 triangular sides and a quadranglar 
  // base.  The mesh has 5 vertices and 5 faces.  
  // The side faces share normals at their common vertices.  The
  // quadrangular base has normals different from the side normal.
  // Coincident vertices that have distinct normals must be
  // duplicated in the vertex list.
  //
  // The apex will be at (1,1.5,4) with normal (0,0,1).
  // The base corners will be at (0,0,0), (0,2,0), (2,3,0), (0,3,0).
 
  bool bHasVertexNormals = true; // we will specify vertex normals
  bool bHasTexCoords = false;    // we will not specify texture coordinates
  const int vertex_count = 5+4;  // 4 duplicates for different base normals
  const int face_count = 5;      // 4 triangle sides and a quad base
  ON_Mesh mesh( face_count, vertex_count, bHasVertexNormals, bHasTexCoords );
 
  // The SetVertex(), SetNormal(), SetTCoord() and SetFace() functions
  // return true if successful and false if input is illegal.  It is
  // a good idea to inspect this returned value.
 
  // vertex #0: apex location and normal
  mesh.SetVertex( 0, ON_3dPoint(1.0,  1.5,  5.0) );
  mesh.SetVertexNormal( 0, ON_3dVector(0.0,  0.0,  1.0) );
 
  // vertex #1: SW corner vertex for sides
  mesh.SetVertex( 1, ON_3dPoint(0.0,  0.0,  0.0) );
  mesh.SetVertexNormal( 1, ON_3dVector(-1.0, -1.0,  0.0) ); // set normal will unitize if needed
 
  // vertex #2: SE corner vertex for sides
  mesh.SetVertex( 2, ON_3dPoint(2.0,  0.0,  0.0) );
  mesh.SetVertexNormal( 2, ON_3dVector(+1.0, -1.0,  0.0) );
 
  // vertex #3: NE corner vertex for sides
  mesh.SetVertex( 3, ON_3dPoint(2.0,  3.0,  0.0) );
  mesh.SetVertexNormal( 3, ON_3dVector(+1.0, +1.0,  0.0) );
 
  // vertex #4: NW corner vertex for sides
  mesh.SetVertex( 4, ON_3dPoint(0.0,  3.0,  0.0) );
  mesh.SetVertexNormal( 4, ON_3dVector(-1.0, +1.0,  0.0) );
 
  // vertex #5: SW corner vertex for base
  mesh.SetVertex( 5, ON_3dPoint(0.0,  0.0,  0.0) ); // == location of v1
  mesh.SetVertexNormal( 5, ON_3dVector(0.0,  0.0, -1.0) );
 
  // vertex #6: SE corner vertex for base
  mesh.SetVertex( 6, ON_3dPoint(2.0,  0.0,  0.0) ); // == location of v2
  mesh.SetVertexNormal( 6, ON_3dVector(0.0,  0.0, -1.0) );
 
  // vertex #7: SW corner vertex for base
  mesh.SetVertex( 7, ON_3dPoint(2.0,  3.0,  0.0) ); // == location of v3
  mesh.SetVertexNormal( 7, ON_3dVector(0.0,  0.0, -1.0) );
 
  // vertex #8: SW corner vertex for base
  mesh.SetVertex( 8, ON_3dPoint(0.0,  3.0,  0.0) ); // == location of v4
  mesh.SetVertexNormal( 8, ON_3dVector(0.0,  0.0, -1.0) );
 
  // Faces have vertices ordered counter-clockwise
 
  // South side triangle
  mesh.SetTriangle( 0, 1, 2, 0 );
 
  // East side triangle
  mesh.SetTriangle( 1, 2, 3, 0 );
 
  // North side triangle
  mesh.SetTriangle( 2, 3, 4, 0 );
 
  // West side triangle
  mesh.SetTriangle( 3, 4, 1, 0 );
 
  // last face is quadrangular base
  mesh.SetQuad( 4, 5, 8, 7, 6 );
 
  //////////////////////////////////////////////////////////////
  //////////////////////////////////////////////////////////////
 
  if( mesh.IsValid() ) 
  {
    // Most applications expect vertex normals.
    // If they are not present, ComputeVertexNormals sets
    // them by averaging face normals.
    if ( !mesh.HasVertexNormals() )
      mesh.ComputeVertexNormals();
 
    context.m_doc.AddMeshObject( mesh );
    context.m_doc.Redraw();
  }
 
  return success;
}

Here is another example:

CRhinoCommand::result CCommandTest::RunCommand(const CRhinoCommandContext& context)
{
  int face_count = 6;
  int vertex_count = 12;
  BOOL bVertexNormals = FALSE;
  BOOL bTextureCoordinates = FALSE;
 
  ON_Mesh mesh( face_count, vertex_count, bVertexNormals, bTextureCoordinates );
  mesh.SetVertex(  0, ON_3fPoint(0.0f, 0.0f, 1.0f) );
  mesh.SetVertex(  1, ON_3fPoint(1.0f, 0.0f, 1.0f) );
  mesh.SetVertex(  2, ON_3fPoint(2.0f, 0.0f, 1.0f) );
  mesh.SetVertex(  3, ON_3fPoint(3.0f, 0.0f, 0.0f) );
  mesh.SetVertex(  4, ON_3fPoint(0.0f, 1.0f, 1.0f) );
  mesh.SetVertex(  5, ON_3fPoint(1.0f, 1.0f, 2.0f) );
  mesh.SetVertex(  6, ON_3fPoint(2.0f, 1.0f, 1.0f) );
  mesh.SetVertex(  7, ON_3fPoint(3.0f, 1.0f, 0.0f) );
  mesh.SetVertex(  8, ON_3fPoint(0.0f, 2.0f, 1.0f) );
  mesh.SetVertex(  9, ON_3fPoint(1.0f, 2.0f, 1.0f) );
  mesh.SetVertex( 10, ON_3fPoint(2.0f, 2.0f, 1.0f) );
  mesh.SetVertex( 11, ON_3fPoint(3.0f, 2.0f, 1.0f) );
  mesh.SetQuad( 0, 0, 1,  5,  4 );
  mesh.SetQuad( 1, 1, 2,  6,  5 );
  mesh.SetQuad( 2, 2, 3,  7,  6 );
  mesh.SetQuad( 3, 4, 5,  9,  8 );
  mesh.SetQuad( 4, 5, 6, 10,  9 );
  mesh.SetQuad( 5, 6, 7, 11, 10 );
  mesh.ComputeVertexNormals();
  mesh.Compact();
 
  context.m_doc.AddMeshObject( mesh );
  context.m_doc.Redraw();
  return CRhinoCommand::success;
}

Public Overrides Function RunCommand(ByVal context As IRhinoCommandContext) As IRhinoCommand.result
  Dim face_count As Integer = 6
  Dim vertex_count As Integer = 12
  Dim bVertexNormals As Boolean = False
  Dim bTextureCoordinates As Boolean = False
 
  Dim mesh As New OnMesh(face_count, vertex_count, bVertexNormals, bTextureCoordinates)
  mesh.SetVertex(0, New On3fPoint(0.0F, 0.0F, 1.0F))
  mesh.SetVertex(1, New On3fPoint(1.0F, 0.0F, 1.0F))
  mesh.SetVertex(2, New On3fPoint(2.0F, 0.0F, 1.0F))
  mesh.SetVertex(3, New On3fPoint(3.0F, 0.0F, 0.0F))
  mesh.SetVertex(4, New On3fPoint(0.0F, 1.0F, 1.0F))
  mesh.SetVertex(5, New On3fPoint(1.0F, 1.0F, 2.0F))
  mesh.SetVertex(6, New On3fPoint(2.0F, 1.0F, 1.0F))
  mesh.SetVertex(7, New On3fPoint(3.0F, 1.0F, 0.0F))
  mesh.SetVertex(8, New On3fPoint(0.0F, 2.0F, 1.0F))
  mesh.SetVertex(9, New On3fPoint(1.0F, 2.0F, 1.0F))
  mesh.SetVertex(10, New On3fPoint(2.0F, 2.0F, 1.0F))
  mesh.SetVertex(11, New On3fPoint(3.0F, 2.0F, 1.0F))
  mesh.SetQuad(0, 0, 1, 5, 4)
  mesh.SetQuad(1, 1, 2, 6, 5)
  mesh.SetQuad(2, 2, 3, 7, 6)
  mesh.SetQuad(3, 4, 5, 9, 8)
  mesh.SetQuad(4, 5, 6, 10, 9)
  mesh.SetQuad(5, 6, 7, 11, 10)
  mesh.ComputeVertexNormals()
  mesh.Compact()
  context.m_doc.AddMeshObject(mesh)
  context.m_doc.Redraw()
  Return IRhinoCommand.result.success
End Function

public override IRhinoCommand.result RunCommand(IRhinoCommandContext context)
{
  int face_count = 6;
  int vertex_count = 12;
  bool bVertexNormals = false ;
  bool bTextureCoordinates = false;
 
  OnMesh mesh = new OnMesh(face_count, vertex_count, bVertexNormals, bTextureCoordinates);
  mesh.SetVertex(  0, new On3fPoint(0.0f, 0.0f, 1.0f) );
  mesh.SetVertex(  1, new On3fPoint(1.0f, 0.0f, 1.0f) );
  mesh.SetVertex(  2, new On3fPoint(2.0f, 0.0f, 1.0f) );
  mesh.SetVertex(  3, new On3fPoint(3.0f, 0.0f, 0.0f) );
  mesh.SetVertex(  4, new On3fPoint(0.0f, 1.0f, 1.0f) );
  mesh.SetVertex(  5, new On3fPoint(1.0f, 1.0f, 2.0f) );
  mesh.SetVertex(  6, new On3fPoint(2.0f, 1.0f, 1.0f) );
  mesh.SetVertex(  7, new On3fPoint(3.0f, 1.0f, 0.0f) );
  mesh.SetVertex(  8, new On3fPoint(0.0f, 2.0f, 1.0f) );
  mesh.SetVertex(  9, new On3fPoint(1.0f, 2.0f, 1.0f) );
  mesh.SetVertex( 10, new On3fPoint(2.0f, 2.0f, 1.0f) );
  mesh.SetVertex( 11, new On3fPoint(3.0f, 2.0f, 1.0f) );
  mesh.SetQuad( 0, 0, 1, 5, 4 );
  mesh.SetQuad( 1, 1, 2, 6, 5 );
  mesh.SetQuad( 2, 2, 3, 7, 6 );
  mesh.SetQuad( 3, 4, 5, 9, 8 );
  mesh.SetQuad( 4, 5, 6, 10, 9 );
  mesh.SetQuad( 5, 6, 7, 11, 10 );
  mesh.ComputeVertexNormals();
  mesh.Compact();
  context.m_doc.AddMeshObject( mesh );
  context.m_doc.Redraw();
  return IRhinoCommand.result.success;
}