The following source code sample demonstrates how to synchronize the basic material color of a layer with the color of the layer. If the layer does not have a material assigned to it, a new material is created and assigned to the layer.

C++

  CRhinoCommand::result CCommandTest::RunCommand(const CRhinoCommandContext& context)
  {
    CRhinoLayerTable& layer_table = context.m_doc.m_layer_table;
    CRhinoMaterialTable& material_table = context.m_doc.m_material_table;
    int num_modified = 0;


    int i, layer_count = layer_table.LayerCount();
    for( i = 0; i < layer_count; i++ )
    {
      const CRhinoLayer& layer = layer_table[i];
      if( layer.IsDeleted() || layer.IsReference() )
        continue;


      int material_index = layer.RenderMaterialIndex();
      if( material_index < 0 )
      {
        // If material_index < 0, then the layer does not have a 
        // material assigned to it. So, we will create a new material
        // that is based on Rhino's default material, and add it
        // to the material table.


        ON_Material material( RhinoApp().AppSettings().DefaultMaterial() );
        material_index = material_table.AddMaterial( material );
        if( material_index >= 0 )
        {
          // Now that we have added the new material,
          // assign it to the layer.
          ON_Layer new_layer( layer );
          new_layer.SetRenderMaterialIndex( material_index );
          layer_table.ModifyLayer( new_layer, layer.LayerIndex() );
        }
      }


      if( material_index < 0 )
        continue;


      const CRhinoMaterial& material = material_table[material_index];
      if( layer.Color() == material.Diffuse() )
        continue;


      // Modify the material's basic, or diffuse, color
      ON_Material new_material( material );
      new_material.SetDiffuse( layer.Color() );
      material_table.ModifyMaterial( new_material, material.MaterialIndex(), FALSE );


      num_modified++;
    }


    if( num_modified > 0 )
      context.m_doc.Regen();
    return CRhinoCommand::success;
  }

VB.NET (Rhino 4)

  Public Overrides Function RunCommand(ByVal context As IRhinoCommandContext) _
    As RMA.Rhino.IRhinoCommand.result


    Dim layer_table As MRhinoLayerTable = context.m_doc.m_layer_table
    Dim material_table As MRhinoMaterialTable = context.m_doc.m_material_table


    Dim num_modified As Integer = 0
    Dim layer_count As Integer = layer_table.LayerCount()


    For i As Integer = 0 To layer_count - 1
      Dim layer As IRhinoLayer = layer_table(i)
      If (layer.IsDeleted() Or layer.IsReference()) Then Continue For


      Dim material_index As Integer = layer.RenderMaterialIndex()
      If (material_index < 0) Then
        ' If material_index < 0, then the layer does not have a 
        ' material assigned to it. So, we will create a new material
        ' that is based on Rhino's default material, and add it
        ' to the material table.
        Dim mat As New OnMaterial(RhUtil.RhinoApp().AppSettings().DefaultMaterial())
        material_index = material_table.AddMaterial(mat)
        If (material_index >= 0) Then
          ' Now that we have added the new material,
          ' assign it to the layer.
          Dim new_layer As New OnLayer(layer)
          new_layer.SetRenderMaterialIndex(material_index)
          layer_table.ModifyLayer(new_layer, layer.LayerIndex())
        End If
      End If


      If (material_index < 0) Then Continue For


      Dim material As IRhinoMaterial = material_table(material_index)
      If (layer.Color().Compare(material.m_diffuse) = 0) Then Continue For


      ' Modify the material's basic, or diffuse, color
      Dim new_material As New OnMaterial(material)
      new_material.m_diffuse = layer.Color()
      material_table.ModifyMaterial(new_material, material.m_material_index, False)
      num_modified = num_modified + 1
    Next


    If (num_modified > 0) Then context.m_doc.Regen()
    Return IRhinoCommand.result.success
  End Function

C# (Rhino 4)

  public override IRhinoCommand.result RunCommand(IRhinoCommandContext context)
  {
    MRhinoLayerTable layer_table = context.m_doc.m_layer_table;
    MRhinoMaterialTable material_table = context.m_doc.m_material_table;
    int num_modified = 0;
    int layer_count = layer_table.LayerCount();


    for( int i=0; i<layer_count; i++ )
    {
      IRhinoLayer layer = layer_table[i];
      if(layer.IsDeleted() || layer.IsReference())
        continue;


      int material_index = layer.RenderMaterialIndex();
      if(material_index < 0)
      {
        // If material_index < 0, then the layer does not have a 
        // material assigned to it. So, we will create a new material
        // that is based on Rhino's default material, and add it
        // to the material table.
        OnMaterial mat = new OnMaterial(RhUtil.RhinoApp().AppSettings().DefaultMaterial());
        material_index = material_table.AddMaterial(mat);
        if(material_index >= 0)
        {
          // Now that we have added the new material,
          // assign it to the layer.
          OnLayer new_layer = new OnLayer(layer);
          new_layer.SetRenderMaterialIndex(material_index);
          layer_table.ModifyLayer(new_layer, layer.LayerIndex());
        }
      }


      if(material_index < 0)
        continue;


      IRhinoMaterial material = material_table[material_index];
      if(layer.Color().Compare(material.m_diffuse) == 0)
        continue;


      // Modify the material's basic, or diffuse, color
      OnMaterial new_material = new OnMaterial(material);
      new_material.m_diffuse = layer.Color();
      material_table.ModifyMaterial(new_material, material.m_material_index, false);
      num_modified++;
    }


    if (num_modified > 0)
      context.m_doc.Regen();
    return IRhinoCommand.result.success;
  }