This occurs when the NoiseChunkGenerator3D#getSlant method is invoked at
a position where the biome has an empty slant holder, currently possible
when using the slant locator addon.

This is fixed by making slant calculation independent of SlantHolders.
Some minor refactoring has also been done as a result of this change.

Prevent exception with other world generators

A reduction of impulse evaluations from 5^2 to 3^2, original algorithm used exponential falloff function which required evaluating impulses from further away to avoid artifacts. I've changed it to a parabolic falloff function which is exactly 0 at the largest possible distance from a cell origin, meaning any cells further than that will not have an effect, preventing said artifacting from occurring. The parabolic function could be replaced with an exponential function (or any other similar easing function) as long as it has an x-intercept at maxCellDistSq. In addition, an option to control whether averaging impulses has been added as it has more of a visual impact with the aforementioned changes.

…h number

…ttps://stackoverflow.com/questions/56039341/get-declared-fields-of-java-lang-reflect-fields-in-jdk12/56043252#56043252)

baased on https://gist.github.com/KdotJPG/882f36b2ae5ae56a8fc91627ec1c87f4

This reverts commit 10d7233.

This reverts commit 1d05f95.