As mentioned in the previous post, we are having issues implementing the manual Geometry Shader part. I posted on the vtkusers mailing list and finally got the attention of Ken from Kitware. He pointed out that we might be missing some uniform variables. He was correct and we made a progress by manually setting the uniform shader. But it does not render as a tube but only as a line. Our next step is to make it work like a tube. After having found the initial glitch, I think either me or David will come up with a correct implementation of the Geometry Shader.
Meanwhile, for the purpose of putting into mailing list, I wrote a small snippet with 3 cases – 1st to render a simple line, 2nd with SetRenderLineAsTubes() and 3rd with Geometry Shader manually being injected into the code. Later, it was pointed out by Elef that we were not specifying any value to the uniform variable linewidthNVC. I manually used vec2(0.1, 0.1) instead of this variable to be able to see the lines on the screen. But also, it was observed that still, it is not tube.
We are hopeful of more progress in coming days, as we now have a better understanding of how Geometry Shaders work.
The code can be seen here.