demystify G76 'R' parameter?

Does anyone know the formula used internally for the g76 degression parameter 'R' and how it interacts with the compound slide angle 'Q' parameter?

I want to do modified flank infeed with control over the angle and depth of cut each pass and at the moment, it's looking like I'm going to have to use a bunch of G33 lines, each with different depth of cut and x/y start/end positions for the flank infeed - a lot of calculations!

Thank you - I'll try installing and running the Python code - this will give me ultimate control

I've been looking at Sandvik's calculator which simplifies a lot of the work, but the export to Excel spreadsheet option doesn't appear to generate valid files.

My quest is for the perfect thread for a worm, with constant helix and smooth flanks to achieve very constant speed in a precision instrument.

Sandvik recommend modified flank infeed over radial infeed to avoid judder and give smooth cutting - their calculator doesn't have brass as an option, but the feed table in the pdf catalogue shows 6 passes, with a final 0.07 mm pass - they strongly advise against using spring passes, which surprised me a bit!