Curves tool creates extreme bumps

[Estecka]

What are you trying to do, and what do you expect to happen?

Blockbench's curve tool has a tendency to create curves with unexpected shapes: unecessary bumps in places that I would expect to be flat, or curves that overshoot their intended height.

This seems to be most noticeable when nodes on the curve are not evenly spaced. The greater the size difference between line segments the more extreme the curve will be on the smaller segment.

What happens instead?

Here are some screnshot comparisons of Blockbench's vs Gimp's curve tool.

These two are the most noticeable cases, All my nodes are on the identity line, so I would expect the curve to be near perfectly flat:

The curves below are closer to what I usually need.

Blockbench's curve will very easily flow off the ceiling/floor, when I would expect it to just kiss the edge in most cases:

Even when the node is below the identity line, the curve still finds a way to flow across and through the ceiling:

Model format in which the issue occurs

Image, Minecraft Skin & Optifine Model

Blockbench variant

Program

Blockbench version

4.11.2

Operating System

Windows 10

Installed Blockbench plugins

None