Minor changes to calculation of interpolated shading value for interpolate at sample.
Minor changes to calculation of interpolated shading value for interpolate at
sample.

jeffbaumes/jeffbaumes-vtk,jeffbaumes/jeffbaumes-vtk,berendkleinhaneveld/VTK,SimVascular/VTK,gram526/VTK,gram526/VTK,berendkleinhaneveld/VTK,hendradarwin/VTK,biddisco/VTK,jmerkow/VTK,candy7393/VTK,aashish24/VTK-old,arnaudgelas/VTK,naucoin/VTKSlicerWidgets,arnaudgelas/VTK,sgh/vtk,keithroe/vtkoptix,johnkit/vtk-dev,sumedhasingla/VTK,sgh/vtk,sumedhasingla/VTK,mspark93/VTK,candy7393/VTK,msmolens/VTK,naucoin/VTKSlicerWidgets,mspark93/VTK,Wuteyan/VTK,ashray/VTK-EVM,msmolens/VTK,candy7393/VTK,sankhesh/VTK,mspark93/VTK,spthaolt/VTK,hendradarwin/VTK,collects/VTK,cjh1/VTK,demarle/VTK,candy7393/VTK,aashish24/VTK-old,gram526/VTK,naucoin/VTKSlicerWidgets,spthaolt/VTK,sankhesh/VTK,berendkleinhaneveld/VTK,Wuteyan/VTK,daviddoria/PointGraphsPhase1,biddisco/VTK,ashray/VTK-EVM,berendkleinhaneveld/VTK,cjh1/VTK,hendradarwin/VTK,spthaolt/VTK,Wuteyan/VTK,jmerkow/VTK,cjh1/VTK,SimVascular/VTK,aashish24/VTK-old,hendradarwin/VTK,arnaudgelas/VTK,demarle/VTK,johnkit/vtk-dev,demarle/VTK,collects/VTK,demarle/VTK,sankhesh/VTK,ashray/VTK-EVM,jeffbaumes/jeffbaumes-vtk,jeffbaumes/jeffbaumes-vtk,naucoin/VTKSlicerWidgets,msmolens/VTK,naucoin/VTKSlicerWidgets,sumedhasingla/VTK,daviddoria/PointGraphsPhase1,candy7393/VTK,msmolens/VTK,ashray/VTK-EVM,jeffbaumes/jeffbaumes-vtk,jmerkow/VTK,mspark93/VTK,biddisco/VTK,keithroe/vtkoptix,collects/VTK,jmerkow/VTK,keithroe/vtkoptix,mspark93/VTK,spthaolt/VTK,daviddoria/PointGraphsPhase1,spthaolt/VTK,sgh/vtk,ashray/VTK-EVM,sankhesh/VTK,candy7393/VTK,berendkleinhaneveld/VTK,sankhesh/VTK,johnkit/vtk-dev,SimVascular/VTK,sgh/vtk,arnaudgelas/VTK,jmerkow/VTK,arnaudgelas/VTK,keithroe/vtkoptix,SimVascular/VTK,cjh1/VTK,sgh/vtk,sumedhasingla/VTK,cjh1/VTK,johnkit/vtk-dev,daviddoria/PointGraphsPhase1,Wuteyan/VTK,sankhesh/VTK,gram526/VTK,SimVascular/VTK,demarle/VTK,SimVascular/VTK,aashish24/VTK-old,biddisco/VTK,sumedhasingla/VTK,msmolens/VTK,ashray/VTK-EVM,keithroe/vtkoptix,jmerkow/VTK,johnkit/vtk-dev,demarle/VTK,berendkleinhaneveld/VTK,spthaolt/VTK,collects/VTK,demarle/VTK,hendradarwin/VTK,msmolens/VTK,spthaolt/VTK,gram526/VTK,gram526/VTK,aashish24/VTK-old,mspark93/VTK,Wuteyan/VTK,demarle/VTK,daviddoria/PointGraphsPhase1,keithroe/vtkoptix,sumedhasingla/VTK,ashray/VTK-EVM,berendkleinhaneveld/VTK,aashish24/VTK-old,cjh1/VTK,candy7393/VTK,mspark93/VTK,daviddoria/PointGraphsPhase1,mspark93/VTK,gram526/VTK,SimVascular/VTK,sgh/vtk,Wuteyan/VTK,SimVascular/VTK,naucoin/VTKSlicerWidgets,hendradarwin/VTK,ashray/VTK-EVM,Wuteyan/VTK,collects/VTK,keithroe/vtkoptix,jeffbaumes/jeffbaumes-vtk,msmolens/VTK,collects/VTK,jmerkow/VTK,msmolens/VTK,jmerkow/VTK,hendradarwin/VTK,sumedhasingla/VTK,biddisco/VTK,arnaudgelas/VTK,johnkit/vtk-dev,keithroe/vtkoptix,biddisco/VTK,johnkit/vtk-dev,biddisco/VTK,sumedhasingla/VTK,sankhesh/VTK,sankhesh/VTK,candy7393/VTK,gram526/VTK