Next we want the height to be lower at the beginning, and then increase dramatically at the end, to form a distinct bulbous droplet.

Here, I'll need the multiplier I used to modulate R earlier. So I go back and rewrite the earlier part so I can re-use the radius multiplier, modulated by ct.

Modulate the radius so it starts a little smaller and grows to full

size at the end of the segment.

ctm =  .7 + .3 * Bias(seg.ct, .3)
mR = R * ctm

Then I add this bit.

Use h for displacement

k = seg.ct ** 15
drop = 1.1 * k / (.1 + k)
drop = drop ** 2.8
hm = ctm + 3.5 * drop
disp = .3 * h * hm

How I come up with formulas like this is complicated. Just take it as a given that it works. The full details of this sort of thing are coming in my shader book. It literally takes pages and pages to explain how to combine exponential functions in interesting ways to intentionally produce specific curves. Designing curve functions is very tricky, but I have a framework that makes it a snap. Someday I'll finish the book...

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