[vtkusers] Problem getting opacity values to work

[Nigel Nunn]

Hi Shawn, 
The division of integers will be part of the problem. 
Try casting both numerators and denominators to double: 
 
  test_opac1 = (test_opac1 - (double(i)/1000.0));
  test_opac2 = (test_opac2 + (double(i)/1000.0));
 
With a debugger, look at the values actually passed 
in test_opac1 and test_opac2;  the integer division 
will produce either zero or 1:

for (i = 0; i < 1400; ++i)
{
  // render the image
  test_opac1 = (test_opac1 - (i/1000));   <--- [1,0] 
  test_opac2 = (test_opac2 + (i/1000));   <--- [0,1] 
  test->SetOpacity(1,test_opac1); 
  test->SetOpacity(2,test_opac2); 
  renderWin->Render(); 
  renderer1->SetActiveCamera(camera); 
} 
 
Nigel 
 
 

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