Summary: How to modify the diffuse color of an exising CRhinoLight object.

The process for modifying a light object is slightly different than the process for modifying other geometric objects, such as points, curves, and surfaces. This is because light objects are stored in a different location in the Rhino document.

Light objects are stored in a CRhinoLightTable object that is held by the active document object. Thus, instead of using one of the ModifyObject() members found on CRhinoDoc, you need to use the ModifyLight() member found on CRhinoLightTable in order to modify an exising light object.

For more details on CRhinoLight and CRhinoLightTable, see rhinoSdkLight.h included with the SDK.

The following example demonstrates how to modify the diffuse color of a light object.

CRhinoCommand::result CCommandTest::RunCommand( const CRhinoCommandContext& context )
{
  // Pick an existing light object
  CRhinoGetObject go;
  go.SetCommandPrompt( L"Select light to change color" );
  go.SetGeometryFilter( CRhinoGetObject::light_object );
  go.GetObjects( 1, 1 );
  if( go.CommandResult() != CRhinoCommand::success )
    return go.CommandResult();
 
  // The the light object
  CRhinoObjRef& ref = go.Object(0);
  const CRhinoLight* light_obj = CRhinoLight::Cast( ref.Object() );
  if( !light_obj )
    return CRhinoCommand::failure;
 
  // Prompt the user to pick a new color
  ON_Color color = light_obj->Light().Diffuse();
  if( !RhinoColorDialog(RhinoApp().MainWnd(), color) )
    CRhinoCommand::cancel;
 
  // Copy the light object's underlying ON_Light
  ON_Light light( light_obj->Light() );
  // Modify the diffuse color
  light.SetDiffuse( color );
 
  // Modify the light
  CRhinoLightTable& light_table = context.m_doc.m_light_table;
  light_table.ModifyLight( light, light_obj->LightIndex() );
 
  return CRhinoCommand::success;
}

Public Overrides Function RunCommand(ByVal context As IRhinoCommandContext)_
  As RMA.Rhino.IRhinoCommand.result
 
  ' Pick an existing light object
  Dim go As New MRhinoGetObject()
  go.SetCommandPrompt("Select light to change color")
  go.SetGeometryFilter(IRhinoGetObject.GEOMETRY_TYPE_FILTER.light_object)
  go.GetObjects(1, 1)
  If (go.CommandResult() <> IRhinoCommand.result.success) Then Return go.CommandResult()
 
  ' The the light object
  Dim objref As MRhinoObjRef = go.Object(0)
  Dim light_obj As IRhinoLight = MRhinoLight.ConstCast(objref.Object())
  If (light_obj Is Nothing) Then Return IRhinoCommand.result.failure
 
  ' Prompt the user to pick a new color
  Dim color As OnColor = light_obj.Light().Diffuse()
  If (Not RhUtil.RhinoColorDialog(RhUtil.RhinoApp.MainWnd(), color)) Then
    Return IRhinoCommand.result.cancel
  End If
 
  ' Copy the light object's underlying ON_Light
  Dim light As New OnLight(light_obj.Light())
  ' Modify the diffuse color
  light.SetDiffuse(color)
 
  ' Modify the light
  Dim light_table As MRhinoLightTable = context.m_doc.m_light_table
  light_table.ModifyLight(light, light_obj.LightIndex())
 
  Return IRhinoCommand.result.success
End Function

public override IRhinoCommand.result RunCommand(IRhinoCommandContext context)
{
  // Pick an existing light object
  MRhinoGetObject go = new MRhinoGetObject();
  go.SetCommandPrompt("Select light to change color");
  go.SetGeometryFilter(IRhinoGetObject.GEOMETRY_TYPE_FILTER.light_object);
  go.GetObjects(1, 1);
  if( go.CommandResult() != IRhinoCommand.result.success )
    return go.CommandResult();
 
  // The the light object
  MRhinoObjRef objref = go.Object(0);
  IRhinoLight light_obj = MRhinoLight.ConstCast(objref.Object());
  if( light_obj == null )
    return IRhinoCommand.result.failure;
 
  // Prompt the user to pick a new color
  OnColor color = light_obj.Light().Diffuse();
  if(!RhUtil.RhinoColorDialog(RhUtil.RhinoApp().MainWnd(), ref color))
    return IRhinoCommand.result.cancel;
 
  // Copy the light object's underlying ON_Light
  OnLight light = new OnLight(light_obj.Light());
  // Modify the diffuse color
  light.SetDiffuse(color);
 
  // Modify the light
  MRhinoLightTable light_table = context.m_doc.m_light_table;
  light_table.ModifyLight(light, light_obj.LightIndex());
 
  return IRhinoCommand.result.success;
}