[vtkusers] Getting color from vtk actor

[Jesse Michael Chandler]

I'm writing a program using VTK to draw objects and render them in 
OpenSG.  Unfortunately, I'm having a problem exporting the color data 
from the actor.  Every example I've found uses MapScalars to get color 
data, yet the call always returns null and I'm a bit puzzled.  My block 
of VTK code is as follows:

vtkSphereSource *sphere = vtkSphereSource::New();
sphere->SetRadius(3.0);
sphere->SetThetaResolution(5);
sphere->setPhiResolution(5);

sphere->Update();

vtkPolyDataMapper *sphereMapper = vtkPolyDataMapper::New();
sphereMapper->SetInput(sphere->GetOutput());

vtkActor *sphereActor = vtkActor::New();
sphereActor->SetMapper(sphereMapper);
sphereActor->GetProperty()->SetColor(.5 , .5 , .5);

vtkUnsignedCharArray *colorArray = 
sphereActor->GetMapper()->MapScalars(1.0);
if(!colorArray)
   printf("Lacking in color.\n");  // this always evaluates...