ENH: Use identical geometry whenever slice faces camera.
ENH: Use identical geometry whenever slice faces camera.

This change ensures that exactly the same quad will be used for the
texture whenever SliceFacesCamera is on.  This avoids z-buffer problems
when blending.

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