Looking for tools for mapgen-related tasks (Voronoi, Perlin)

[Wuzzy]

Accoding to lua_api.txt (README file for Minetest modders), biomes are defined as points in a Voronoi diagram.
I can recall that paramat once posted a screenshot showing a software to align these points in the Vonoroi diagram for the mapgen in Minetest Game.

As far I understand, getting the heat and humidty points of the biomes right is VERY important and I suppose it is very hard to balance them blindly (that is, without any visualization).

So, does anyone here know a tool to experiment with Voronoi diagrams which is not GeoGebra?

Second question: Are there software tools around to experiment with Perlin noise parameters? For the mapgen decorations, you can specify noise parameters, but getting those right is also very difficult and extremely annoying to do. If there would be a tool for giving me at least some sort of preview for perlin noise. I want to fiddle around with parameters in real time and see instantly what happens. It does not have to be Minetest-specific, it is enough if I get a 2D output or something.

This would save me hours of time wasted in restarting the subgame 1,000,000 times. ;-)

[TumeniNodes]

Not sure if this fits your needs.

I fell upon it but I was unable to get it to run via WINE so be careful it freezes and does not uninstall properly either...
So I never got a chance to play around with it

http://visual-terrain-maker.en.lo4d.com/

most of the tools similar to what you are wanting, which I saw are 'spensive" : /