You're right.
I gather that variable ridge heights could just be same-slope cones from each drain point. And variable drain heights the same, but cones starting from fixed ridges and determining the drain heights by cones, again.

Sorry to waste your time, blame me for being a geometric nerd. 😜

I'm just trying to find the best 3D-geometric way to drain water. Voronoi will give optimal distance from ridge to drain hole, but different slope gradients. I'm guessing this isn't solvable.

Let's say I want to design a terrain or a flat roof. I only have certain lowest points where the water can be drained, at equal height. I also have a max height of the ridges. Because otherwise i would just raise the ridges conferring to circles from all the lowest-points-of-drainiage.

1963. But true nonetheless
da.wikipedia.org/wiki/Hvis_de...