Problem
Imagine you have two objects: a surface and a line curve and you would like to setup cage editing, with the surface as the captive object and the line curve as the control object.
Solution
To allow the line curve to control the surface, you will need to create a CRhinoMorphControl object. A CRhinoMorphControl object has a ON_MorphControl object, as its data member, which contains the definition of the controlling object (in this case, line).
Once you have properly defined the ON_MorphControl object and created the runtime CRhinoMorphControl object, you can use the RhinoCaptureObject API function to setup the “capture.”
The following example code demonstrates how you might write a command that allows a surface to be controlled by a line…
CRhinoCommand::result CCommandTest::RunCommand( const CRhinoCommandContext& context )
{
ON_Workspace ws;
CRhinoCommand::result rc = CRhinoCommand::success;
// Get the captive object
CRhinoGetObject go;
go.SetCommandPrompt( L"Select captive surface or polysurface" );
go.SetGeometryFilter( CRhinoGetObject::surface_object | CRhinoGetObject::polysrf_object );
go.GetObjects( 1, 1 );
rc = go.CommandResult();
if( CRhinoCommand::success != rc )
return rc;
const CRhinoObject* captive = go.Object(0).Object();
if( 0 == captive )
return CRhinoCommand::failure;
// Define the control line
ON_Line line;
rc = RhinoGetLine( CArgsRhinoGetLine(), line );
if( CRhinoCommand::success != rc )
return rc;
// Get the curve parameters
int degree = 3;
int cv_count = 4;
for(;;)
{
CRhinoGetOption gl;
gl.SetCommandPrompt( L"NURBS Parameters" );
gl.AcceptNothing();
int d_opt = gl.AddCommandOptionInteger( RHCMDOPTNAME(L"Degree"), °ree, L"Curve degree", 1.0, 100.0 );
int p_opt = gl.AddCommandOptionInteger( RHCMDOPTNAME(L"PointCount"), &cv_count, L"Number of control points", 2.0, 100.0 );
gl.GetOption();
rc = gl.CommandResult();
if( CRhinoCommand::success != rc )
return rc;
if( CRhinoGet::nothing == gl.Result() )
break;
if( cv_count <= degree )
{
if( CRhinoGet::option != gl.Result() )
continue;
const CRhinoCommandOption* opt = go.Option();
if( 0 == opt )
continue;
if( d_opt == opt->m_option_index )
cv_count = degree + 1;
else
degree = cv_count - 1;
}
}
// Set up morph control
ON_MorphControl* control = new ON_MorphControl();
control->m_varient = 1; // 1= curve
// Specify the source line curve
control->m_nurbs_curve0.Create( 3, false, 2, 2 );
control->m_nurbs_curve0.MakeClampedUniformKnotVector();
control->m_nurbs_curve0.SetCV( 0, line.from );
control->m_nurbs_curve0.SetCV( 1, line.to );
// Specify the destination NURBS curve
control->m_nurbs_curve.Create( 3, false, degree + 1, cv_count );
control->m_nurbs_curve.MakeClampedUniformKnotVector();
double* g = ws.GetDoubleMemory( control->m_nurbs_curve.m_cv_count );
control->m_nurbs_curve.GetGrevilleAbcissae( g );
ON_Interval d = control->m_nurbs_curve.Domain();
double s = 0.0;
int i;
for( i = 0; i < control->m_nurbs_curve.m_cv_count; i++ )
{
s = d.NormalizedParameterAt( g[i] );
control->m_nurbs_curve.SetCV( i, line.PointAt(s) );
}
// Make sure domains match
s = line.Length();
if( s > ON_SQRT_EPSILON )
control->m_nurbs_curve0.SetDomain( 0.0, s );
d = control->m_nurbs_curve0.Domain();
control->m_nurbs_curve.SetDomain( d[0], d[1] );
// Create the morph control object
CRhinoMorphControl* control_object = new CRhinoMorphControl();
control_object->SetControl( control );
context.m_doc.AddObject( control_object );
// Set up the capture
RhinoCaptureObject( control_object, const_cast<CRhinoObject*>(captive) );
// Clean up display
context.m_doc.UnselectAll();
// Turn on the control grips
control_object->EnableGrips( true );
context.m_doc.Redraw( CRhinoView::mark_display_hint );
return rc;
}
