@Ron: Could you provide the FPS for the following cases:

(1) Regular Slicer binary GPU VR
(2) Regular Slicer binary CPU VR
(3) OpenGL2 Slicer binary GPU VR
(4) OpenGL2 Slicer binary CPU VR

FPS can be displayed clicking on the "..." in the 3D view controller panel.

Could you also provide info about the GPU card installer on your workstation ?

GPU card: NVIDIA GeForce GT 750M 2048 MB

VTKOpenGL2 backend (based of VTK d733280):

• GPU rendering: 7 fps
• CPU rendering: 17 fps

I used one of the slicer sample data sets (chest, see under welcome module, sample data sets), one of the presets (chest-contrast-enhanced) and ROI clipping. I slightly modulated the preset using the shift transfer function in the VR module panel. This should be perfectly reproducible to the vkt team and allow them to measure any additional metrics that they need. I do not have access to the regular Slicer with the same SVN number and I already provided
Item 3 and 4 from note https://issues.slicer.org/view.php?id=3951#c12891. I think that it is critical that the VTK team try for themselves in order to see what I am referring to.

VTK rendering experts are looking at profiling OpenGL code to see where the GPU mapper can be improved.

revisit this with OpenGL2 backend

@kikinis Since the nightly build of Slicer now include the newer VTK OpenGL2 backend, is this still an issue ?

Following last exchange with @kikinis , the GPU rendering is now behaving much better.