Hopefully, this post will save some future Max user from scratching their head. I was gobsmacked today to discover that the position of a slider in a patcher affects its output values.
My float slider (0…1) pan control wasn't reliably hitting 0.5. Ok, that's a common problem with resolution or using odd-numbered box sizes or something. Easy to fix, right? But I checked. No problems . What the heck? This controller works for a while, then I'll edit make a few cosmetic changes, and it stops hitting 0.5 again. I just couldn't nail down the problem for days.
Long story short: it turns that a float slider sitting on a fractional pixel boundary outputs slightly different values than a float slider sitting on a whole number pixel boundary. Yep. The output values (interpolation) of a slider differs when the slider position is x=50 y=100 vs x=50 y=100.5. So every time you move a slider a fraction of a pixel, you risk changing its output.
In short, it's easy to get a 0…1 slider to hit 0.5 in the middle every time. Don't use odd-numbered box sizes and don't place your float sliders on a fractional pixel. Use snap to grid or manually set the position to a whole number.
But that hurt my brain a bit.