Add giant crystal geodes

[Treer]

Proof-of-concept demoing how someone might make use of the spare region in the Nether.

Crystal geode fissure / entrance

Inside

Video demo of the Mantle (already part of the Nether mod) and how the Mantle can be used to reach the previously unused region of the nether, which this PR turns into crystalline structures.

Very few players will ever cross the Mantle and visit the secondary region of the Nether, so there's a lot of freedom to play here. I don't want to monopolize the last unused region in the Nether, but if I don't kick this off I don't think anyone else is going to.

Tthe geode crystal name needs work, I called it beryl because red beryl is close to what I was going for, but I don't think its a good name. Also, it can be crafted into netherglass panes and the glass texture is currently as bad as the name.

duane suggested bands of colour, which is a good idea, but I'll have to think where/what that should look like.

Red Beryl:

[SmallJoker]

Hmm. Looks good so far, but I think blending the two "biomes" would look even better. i.e. add subtle randomness to noise values. That will cause the two areas to mix a bit.

EDIT: Also replacing everything seems a bit off. Regular stone would still be nice to see every now and then for some variety.

[Treer]

Could you expand on that? Do you mean blending the transition between deep netherrack and crystal?

Geodes often have a sharp transition, but there are often bands of color changes too, which the nether geode is missing. Like the white here: (Not that reality is in any way a requirement)

Duane suggested more colour variance in the crystals, which I'm starting to play with but haven't made progress worth posting about.

It does feel like it's not "there yet", so I appreciate posts like this trying to put a finger on what's a bit off, and what it would be nice to see. The walls will have to change, but I haven't figured out to what.

[SmallJoker]

Oh I see! I should've really looked up how these look like. Makes sense to have sharp edges.

I am only a bit concerned that they might occur too often, and replacing stone entirely.

[Treer]

I have a suspicion that they will be too hard to find and nobody ever will :)

I doubt many people will even reach the mantle, but it's hard to say.

Edit: Stone is already replaced entirely in the nether, either by netherack or deep netherack, I take it by "stone" you meant something more like that?

[tenplus1]

I added this pull to my own nether mod and I gotta say, stumbling across one of these geode areas looks amazing! I would add this change in a heartbeat ( gotta fix the lasty lastz locals in mapgen_geaodes.lua first tho :)

[Treer]

Cheers, I've rebased it and fixed that lasty lastz issue and a couple of other things. (I hope PR rebases don't create too many headaches)

There's more could be done with the lighting, and some colour variance. I have a branch off this one to try and play with that stuff, but it's on the backburner. A white transition mineral like in the amethyst geode photo could also work.

[tenplus1]

@Treer - kewl, changes have been added to Xanadu server for testing :) players love it.

[SmallJoker]

Is there a specific license for the textures? If so, please document it. If the PR is otherwise ready for merge, I will merge it a few days after addressing this question.

[Treer]

Edit: Licensing for textures is now sorted. lets merge it

If anyone is interested, I've pushed the branch where I was playing with more color to https://github.com/Treer/nether/tree/feature/geodes-colour (I stopped working on it)

[Treer]

I will merge it a few days after addressing this question.

It's ready