
The Heeelix demo has been ported to GeeXLab (OpenGL 2.1). I didn’t test on all platforms but this demo should run on Windows, Linux, macOS. In theory, it should be work on Raspberry Pi but in practice, I think the pixel shader is a little bit too heavy for the VideoCore IV GPU.
Heeelix won the first place at the Revision 2018 party animated gif compo.
The pixel shader is ready to be live-coded. Just run the demo (gl21-heeelix.xml) in GeeXLab, edit the pixel shader in your favorite text editor and hack the demo!
The GeeXLab demo can be downloaded from THIS LINK. The latest GeeXLab (Windows, Linux or macOS) is available on THIS PAGE.
For any feedback, a thread on Geeks3D forums is available HERE.
On my GTX 1080, it takes around 2 seconds to compile the GLSL pixel shader each time you add a new modification. If the modification is already known by the GLSL compiler, the update is extremely fast.
Heeelix runs at 174 FPS (res: 800×480) on a GeForce GTX 1080 + R391.35.
If you uncomment the line 14 of the pixel shader (ANOTHER_LEVEL) you will get:

And if you add two extra levels:
#ifdef ANOTHER_LEVEL
scale *= pModHelixScale(p, lead, innerRatio);
p.x *= -1.;
scale *= pModHelixScale(p, lead, innerRatio);
p.x *= -1.;
scale *= pModHelixScale(p, lead, innerRatio);
p.x *= -1.;
#endif
