minetest/src/mapgen/mapgen_v7.cpp

/*
Minetest
Copyright (C) 2013-2018 kwolekr, Ryan Kwolek <kwolekr@minetest.net>
Copyright (C) 2014-2018 paramat

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/


#include "mapgen.h"
#include <cmath>
#include "voxel.h"
#include "noise.h"
#include "mapblock.h"
#include "mapnode.h"
#include "map.h"
#include "content_sao.h"
#include "nodedef.h"
#include "voxelalgorithms.h"
//#include "profiler.h" // For TimeTaker
#include "settings.h" // For g_settings
#include "emerge.h"
#include "dungeongen.h"
#include "cavegen.h"
#include "mg_biome.h"
#include "mg_ore.h"
#include "mg_decoration.h"
#include "mapgen_v7.h"


FlagDesc flagdesc_mapgen_v7[] = {
	{"mountains",   MGV7_MOUNTAINS},
	{"ridges",      MGV7_RIDGES},
	{"floatlands",  MGV7_FLOATLANDS},
	{"caverns",     MGV7_CAVERNS},
	{NULL,          0}
};


////////////////////////////////////////////////////////////////////////////////


MapgenV7::MapgenV7(int mapgenid, MapgenV7Params *params, EmergeManager *emerge)
	: MapgenBasic(mapgenid, params, emerge)
{
	spflags              = params->spflags;
	mount_zero_level     = params->mount_zero_level;
	float_mount_density  = params->float_mount_density;
	float_mount_exponent = params->float_mount_exponent;
	floatland_level      = params->floatland_level;
	shadow_limit         = params->shadow_limit;

	cave_width           = params->cave_width;
	large_cave_depth     = params->large_cave_depth;
	lava_depth           = params->lava_depth;
	cavern_limit         = params->cavern_limit;
	cavern_taper         = params->cavern_taper;
	cavern_threshold     = params->cavern_threshold;
	dungeon_ymin         = params->dungeon_ymin;
	dungeon_ymax         = params->dungeon_ymax;

	// This is to avoid a divide-by-zero.
	// Parameter will be saved to map_meta.txt in limited form.
	params->float_mount_height = std::fmax(params->float_mount_height, 1.0f);
	float_mount_height   = params->float_mount_height;

	// 2D noise
	noise_terrain_base =
		new Noise(&params->np_terrain_base,    seed, csize.X, csize.Z);
	noise_terrain_alt =
		new Noise(&params->np_terrain_alt,     seed, csize.X, csize.Z);
	noise_terrain_persist =
		new Noise(&params->np_terrain_persist, seed, csize.X, csize.Z);
	noise_height_select =
		new Noise(&params->np_height_select,   seed, csize.X, csize.Z);
	noise_filler_depth =
		new Noise(&params->np_filler_depth,    seed, csize.X, csize.Z);

	if (spflags & MGV7_MOUNTAINS)
		noise_mount_height =
			new Noise(&params->np_mount_height,      seed, csize.X, csize.Z);

	if (spflags & MGV7_FLOATLANDS) {
		noise_floatland_base =
			new Noise(&params->np_floatland_base,    seed, csize.X, csize.Z);
		noise_float_base_height =
			new Noise(&params->np_float_base_height, seed, csize.X, csize.Z);
	}

	if (spflags & MGV7_RIDGES) {
		noise_ridge_uwater =
			new Noise(&params->np_ridge_uwater,      seed, csize.X, csize.Z);
	// 3D noise, 1 up, 1 down overgeneration
		noise_ridge =
			new Noise(&params->np_ridge,    seed, csize.X, csize.Y + 2, csize.Z);
	}

	// 3D noise, 1 up, 1 down overgeneration
	if ((spflags & MGV7_MOUNTAINS) || (spflags & MGV7_FLOATLANDS))
		noise_mountain =
			new Noise(&params->np_mountain, seed, csize.X, csize.Y + 2, csize.Z);

	// 3D noise, 1 down overgeneration
	MapgenBasic::np_cave1  = params->np_cave1;
	MapgenBasic::np_cave2  = params->np_cave2;
	MapgenBasic::np_cavern = params->np_cavern;
}


MapgenV7::~MapgenV7()
{
	delete noise_terrain_base;
	delete noise_terrain_alt;
	delete noise_terrain_persist;
	delete noise_height_select;
	delete noise_filler_depth;

	if (spflags & MGV7_MOUNTAINS)
		delete noise_mount_height;

	if (spflags & MGV7_FLOATLANDS) {
		delete noise_floatland_base;
		delete noise_float_base_height;
	}

	if (spflags & MGV7_RIDGES) {
		delete noise_ridge_uwater;
		delete noise_ridge;
	}

	if ((spflags & MGV7_MOUNTAINS) || (spflags & MGV7_FLOATLANDS))
		delete noise_mountain;
}


MapgenV7Params::MapgenV7Params():
	np_terrain_base      (4.0,   70.0,  v3f(600,  600,  600),  82341, 5, 0.6,  2.0),
	np_terrain_alt       (4.0,   25.0,  v3f(600,  600,  600),  5934,  5, 0.6,  2.0),
	np_terrain_persist   (0.6,   0.1,   v3f(2000, 2000, 2000), 539,   3, 0.6,  2.0),
	np_height_select     (-8.0,  16.0,  v3f(500,  500,  500),  4213,  6, 0.7,  2.0),
	np_filler_depth      (0.0,   1.2,   v3f(150,  150,  150),  261,   3, 0.7,  2.0),
	np_mount_height      (256.0, 112.0, v3f(1000, 1000, 1000), 72449, 3, 0.6,  2.0),
	np_ridge_uwater      (0.0,   1.0,   v3f(1000, 1000, 1000), 85039, 5, 0.6,  2.0),
	np_floatland_base    (-0.6,  1.5,   v3f(600,  600,  600),  114,   5, 0.6,  2.0),
	np_float_base_height (48.0,  24.0,  v3f(300,  300,  300),  907,   4, 0.7,  2.0),
	np_mountain          (-0.6,  1.0,   v3f(250,  350,  250),  5333,  5, 0.63, 2.0),
	np_ridge             (0.0,   1.0,   v3f(100,  100,  100),  6467,  4, 0.75, 2.0),
	np_cavern            (0.0,   1.0,   v3f(384,  128,  384),  723,   5, 0.63, 2.0),
	np_cave1             (0.0,   12.0,  v3f(61,   61,   61),   52534, 3, 0.5,  2.0),
	np_cave2             (0.0,   12.0,  v3f(67,   67,   67),   10325, 3, 0.5,  2.0)
{
}


void MapgenV7Params::readParams(const Settings *settings)
{
	settings->getFlagStrNoEx("mgv7_spflags", spflags, flagdesc_mapgen_v7);
	settings->getS16NoEx("mgv7_mount_zero_level",       mount_zero_level);
	settings->getFloatNoEx("mgv7_cave_width",           cave_width);
	settings->getS16NoEx("mgv7_large_cave_depth",       large_cave_depth);
	settings->getS16NoEx("mgv7_lava_depth",             lava_depth);
	settings->getFloatNoEx("mgv7_float_mount_density",  float_mount_density);
	settings->getFloatNoEx("mgv7_float_mount_height",   float_mount_height);
	settings->getFloatNoEx("mgv7_float_mount_exponent", float_mount_exponent);
	settings->getS16NoEx("mgv7_floatland_level",        floatland_level);
	settings->getS16NoEx("mgv7_shadow_limit",           shadow_limit);
	settings->getS16NoEx("mgv7_cavern_limit",           cavern_limit);
	settings->getS16NoEx("mgv7_cavern_taper",           cavern_taper);
	settings->getFloatNoEx("mgv7_cavern_threshold",     cavern_threshold);
	settings->getS16NoEx("mgv7_dungeon_ymin",           dungeon_ymin);
	settings->getS16NoEx("mgv7_dungeon_ymax",           dungeon_ymax);

	settings->getNoiseParams("mgv7_np_terrain_base",      np_terrain_base);
	settings->getNoiseParams("mgv7_np_terrain_alt",       np_terrain_alt);
	settings->getNoiseParams("mgv7_np_terrain_persist",   np_terrain_persist);
	settings->getNoiseParams("mgv7_np_height_select",     np_height_select);
	settings->getNoiseParams("mgv7_np_filler_depth",      np_filler_depth);
	settings->getNoiseParams("mgv7_np_mount_height",      np_mount_height);
	settings->getNoiseParams("mgv7_np_ridge_uwater",      np_ridge_uwater);
	settings->getNoiseParams("mgv7_np_floatland_base",    np_floatland_base);
	settings->getNoiseParams("mgv7_np_float_base_height", np_float_base_height);
	settings->getNoiseParams("mgv7_np_mountain",          np_mountain);
	settings->getNoiseParams("mgv7_np_ridge",             np_ridge);
	settings->getNoiseParams("mgv7_np_cavern",            np_cavern);
	settings->getNoiseParams("mgv7_np_cave1",             np_cave1);
	settings->getNoiseParams("mgv7_np_cave2",             np_cave2);
}


void MapgenV7Params::writeParams(Settings *settings) const
{
	settings->setFlagStr("mgv7_spflags", spflags, flagdesc_mapgen_v7, U32_MAX);
	settings->setS16("mgv7_mount_zero_level",       mount_zero_level);
	settings->setFloat("mgv7_cave_width",           cave_width);
	settings->setS16("mgv7_large_cave_depth",       large_cave_depth);
	settings->setS16("mgv7_lava_depth",             lava_depth);
	settings->setFloat("mgv7_float_mount_density",  float_mount_density);
	settings->setFloat("mgv7_float_mount_height",   float_mount_height);
	settings->setFloat("mgv7_float_mount_exponent", float_mount_exponent);
	settings->setS16("mgv7_floatland_level",        floatland_level);
	settings->setS16("mgv7_shadow_limit",           shadow_limit);
	settings->setS16("mgv7_cavern_limit",           cavern_limit);
	settings->setS16("mgv7_cavern_taper",           cavern_taper);
	settings->setFloat("mgv7_cavern_threshold",     cavern_threshold);
	settings->setS16("mgv7_dungeon_ymin",           dungeon_ymin);
	settings->setS16("mgv7_dungeon_ymax",           dungeon_ymax);

	settings->setNoiseParams("mgv7_np_terrain_base",      np_terrain_base);
	settings->setNoiseParams("mgv7_np_terrain_alt",       np_terrain_alt);
	settings->setNoiseParams("mgv7_np_terrain_persist",   np_terrain_persist);
	settings->setNoiseParams("mgv7_np_height_select",     np_height_select);
	settings->setNoiseParams("mgv7_np_filler_depth",      np_filler_depth);
	settings->setNoiseParams("mgv7_np_mount_height",      np_mount_height);
	settings->setNoiseParams("mgv7_np_ridge_uwater",      np_ridge_uwater);
	settings->setNoiseParams("mgv7_np_floatland_base",    np_floatland_base);
	settings->setNoiseParams("mgv7_np_float_base_height", np_float_base_height);
	settings->setNoiseParams("mgv7_np_mountain",          np_mountain);
	settings->setNoiseParams("mgv7_np_ridge",             np_ridge);
	settings->setNoiseParams("mgv7_np_cavern",            np_cavern);
	settings->setNoiseParams("mgv7_np_cave1",             np_cave1);
	settings->setNoiseParams("mgv7_np_cave2",             np_cave2);
}


////////////////////////////////////////////////////////////////////////////////


int MapgenV7::getSpawnLevelAtPoint(v2s16 p)
{
	// If rivers are enabled, first check if in a river
	if (spflags & MGV7_RIDGES) {
		float width = 0.2f;
		float uwatern = NoisePerlin2D(&noise_ridge_uwater->np, p.X, p.Y, seed) *
			2.0f;
		if (std::fabs(uwatern) <= width)
			return MAX_MAP_GENERATION_LIMIT; // Unsuitable spawn point
	}

	// Terrain noise 'offset' is the average level of that terrain.
	// At least 50% of terrain will be below the higher of base and alt terrain
	// 'offset's.
	// Raising the maximum spawn level above 'water_level + 16' is necessary
	// for when terrain 'offset's are set much higher than water_level.
	s16 max_spawn_y = std::fmax(std::fmax(noise_terrain_alt->np.offset,
			noise_terrain_base->np.offset),
			water_level + 16);
	// Base terrain calculation
	s16 y = baseTerrainLevelAtPoint(p.X, p.Y);

	// If mountains are disabled, terrain level is base terrain level.
	// Avoids mid-air spawn where mountain terrain would have been.
	if (!(spflags & MGV7_MOUNTAINS)) {
		if (y < water_level || y > max_spawn_y)
			return MAX_MAP_GENERATION_LIMIT; // Unsuitable spawn point

		// y + 2 because y is surface level and due to biome 'dust'
		return y + 2;
	}

	// Search upwards for first node without mountain terrain
	int iters = 256;
	while (iters > 0 && y <= max_spawn_y) {
		if (!getMountainTerrainAtPoint(p.X, y + 1, p.Y)) {
			if (y <= water_level || y > max_spawn_y)
				return MAX_MAP_GENERATION_LIMIT; // Unsuitable spawn point

			// y + 1 due to biome 'dust'
			return y + 1;
		}
		y++;
		iters--;
	}

	// Unsuitable spawn point
	return MAX_MAP_GENERATION_LIMIT;
}


void MapgenV7::makeChunk(BlockMakeData *data)
{
	// Pre-conditions
	assert(data->vmanip);
	assert(data->nodedef);
	assert(data->blockpos_requested.X >= data->blockpos_min.X &&
		data->blockpos_requested.Y >= data->blockpos_min.Y &&
		data->blockpos_requested.Z >= data->blockpos_min.Z);
	assert(data->blockpos_requested.X <= data->blockpos_max.X &&
		data->blockpos_requested.Y <= data->blockpos_max.Y &&
		data->blockpos_requested.Z <= data->blockpos_max.Z);

	//TimeTaker t("makeChunk");

	this->generating = true;
	this->vm = data->vmanip;
	this->ndef = data->nodedef;

	v3s16 blockpos_min = data->blockpos_min;
	v3s16 blockpos_max = data->blockpos_max;
	node_min = blockpos_min * MAP_BLOCKSIZE;
	node_max = (blockpos_max + v3s16(1, 1, 1)) * MAP_BLOCKSIZE - v3s16(1, 1, 1);
	full_node_min = (blockpos_min - 1) * MAP_BLOCKSIZE;
	full_node_max = (blockpos_max + 2) * MAP_BLOCKSIZE - v3s16(1, 1, 1);

	blockseed = getBlockSeed2(full_node_min, seed);

	// Generate base and mountain terrain
	s16 stone_surface_max_y = generateTerrain();

	// Generate rivers
	if (spflags & MGV7_RIDGES)
		generateRidgeTerrain();

	// Create heightmap
	updateHeightmap(node_min, node_max);

	// Init biome generator, place biome-specific nodes, and build biomemap
	if (flags & MG_BIOMES) {
		biomegen->calcBiomeNoise(node_min);
		generateBiomes();
	}

	// Generate tunnels, caverns and large randomwalk caves
	if (flags & MG_CAVES) {
		// Generate tunnels first as caverns confuse them
		generateCavesNoiseIntersection(stone_surface_max_y);

		// Generate caverns
		bool near_cavern = false;
		if (spflags & MGV7_CAVERNS)
			near_cavern = generateCavernsNoise(stone_surface_max_y);

		// Generate large randomwalk caves
		if (near_cavern)
			// Disable large randomwalk caves in this mapchunk by setting
			// 'large cave depth' to world base. Avoids excessive liquid in
			// large caverns and floating blobs of overgenerated liquid.
			generateCavesRandomWalk(stone_surface_max_y,
				-MAX_MAP_GENERATION_LIMIT);
		else
			generateCavesRandomWalk(stone_surface_max_y, large_cave_depth);
	}

	// Generate the registered ores
	m_emerge->oremgr->placeAllOres(this, blockseed, node_min, node_max);

	// Generate dungeons
	if ((flags & MG_DUNGEONS) && full_node_min.Y >= dungeon_ymin &&
			full_node_max.Y <= dungeon_ymax)
		generateDungeons(stone_surface_max_y);

	// Generate the registered decorations
	if (flags & MG_DECORATIONS)
		m_emerge->decomgr->placeAllDecos(this, blockseed, node_min, node_max);

	// Sprinkle some dust on top after everything else was generated
	if (flags & MG_BIOMES)
		dustTopNodes();

	// Update liquids
	updateLiquid(&data->transforming_liquid, full_node_min, full_node_max);

	// Calculate lighting.
	// Limit floatland shadow.
	bool propagate_shadow = !((spflags & MGV7_FLOATLANDS) &&
		node_min.Y <= shadow_limit && node_max.Y >= shadow_limit);

	if (flags & MG_LIGHT)
		calcLighting(node_min - v3s16(0, 1, 0), node_max + v3s16(0, 1, 0),
			full_node_min, full_node_max, propagate_shadow);

	this->generating = false;

	//printf("makeChunk: %lums\n", t.stop());
}


////////////////////////////////////////////////////////////////////////////////


float MapgenV7::baseTerrainLevelAtPoint(s16 x, s16 z)
{
	float hselect = NoisePerlin2D(&noise_height_select->np, x, z, seed);
	hselect = rangelim(hselect, 0.0f, 1.0f);

	float persist = NoisePerlin2D(&noise_terrain_persist->np, x, z, seed);

	noise_terrain_base->np.persist = persist;
	float height_base = NoisePerlin2D(&noise_terrain_base->np, x, z, seed);

	noise_terrain_alt->np.persist = persist;
	float height_alt = NoisePerlin2D(&noise_terrain_alt->np, x, z, seed);

	if (height_alt > height_base)
		return height_alt;

	return (height_base * hselect) + (height_alt * (1.0f - hselect));
}


float MapgenV7::baseTerrainLevelFromMap(int index)
{
	float hselect = rangelim(noise_height_select->result[index], 0.0f, 1.0f);
	float height_base = noise_terrain_base->result[index];
	float height_alt = noise_terrain_alt->result[index];

	if (height_alt > height_base)
		return height_alt;

	return (height_base * hselect) + (height_alt * (1.0f - hselect));
}


bool MapgenV7::getMountainTerrainAtPoint(s16 x, s16 y, s16 z)
{
	float mnt_h_n =
		std::fmax(NoisePerlin2D(&noise_mount_height->np, x, z, seed), 1.0f);
	float density_gradient = -((float)(y - mount_zero_level) / mnt_h_n);
	float mnt_n = NoisePerlin3D(&noise_mountain->np, x, y, z, seed);

	return mnt_n + density_gradient >= 0.0f;
}


bool MapgenV7::getMountainTerrainFromMap(int idx_xyz, int idx_xz, s16 y)
{
	float mounthn = std::fmax(noise_mount_height->result[idx_xz], 1.0f);
	float density_gradient = -((float)(y - mount_zero_level) / mounthn);
	float mountn = noise_mountain->result[idx_xyz];

	return mountn + density_gradient >= 0.0f;
}


bool MapgenV7::getFloatlandMountainFromMap(int idx_xyz, int idx_xz, s16 y)
{
	// Make rim 2 nodes thick to match floatland base terrain
	float density_gradient = (y >= floatland_level) ?
		-std::pow((float)(y - floatland_level) / float_mount_height,
		float_mount_exponent) :
		-std::pow((float)(floatland_level - 1 - y) / float_mount_height,
		float_mount_exponent);

	float floatn = noise_mountain->result[idx_xyz] + float_mount_density;

	return floatn + density_gradient >= 0.0f;
}


void MapgenV7::floatBaseExtentFromMap(s16 *float_base_min, s16 *float_base_max,
	int idx_xz)
{
	// '+1' to avoid a layer of stone at y = MAX_MAP_GENERATION_LIMIT
	s16 base_min = MAX_MAP_GENERATION_LIMIT + 1;
	s16 base_max = MAX_MAP_GENERATION_LIMIT;

	float n_base = noise_floatland_base->result[idx_xz];
	if (n_base > 0.0f) {
		float n_base_height =
				std::fmax(noise_float_base_height->result[idx_xz], 1.0f);
		float amp = n_base * n_base_height;
		float ridge = n_base_height / 3.0f;
		base_min = floatland_level - amp / 1.5f;

		if (amp > ridge * 2.0f) {
			// Lake bed
			base_max = floatland_level - (amp - ridge * 2.0f) / 2.0f;
		} else {
			// Hills and ridges
			float diff = std::fabs(amp - ridge) / ridge;
			// Smooth ridges using the 'smoothstep function'
			float smooth_diff = diff * diff * (3.0f - 2.0f * diff);
			base_max = floatland_level + ridge - smooth_diff * ridge;
		}
	}

	*float_base_min = base_min;
	*float_base_max = base_max;
}


int MapgenV7::generateTerrain()
{
	MapNode n_air(CONTENT_AIR);
	MapNode n_stone(c_stone);
	MapNode n_water(c_water_source);

	//// Calculate noise for terrain generation
	noise_terrain_persist->perlinMap2D(node_min.X, node_min.Z);
	float *persistmap = noise_terrain_persist->result;

	noise_terrain_base->perlinMap2D(node_min.X, node_min.Z, persistmap);
	noise_terrain_alt->perlinMap2D(node_min.X, node_min.Z, persistmap);
	noise_height_select->perlinMap2D(node_min.X, node_min.Z);

	if ((spflags & MGV7_MOUNTAINS) || (spflags & MGV7_FLOATLANDS)) {
		noise_mountain->perlinMap3D(node_min.X, node_min.Y - 1, node_min.Z);
	}

	if (spflags & MGV7_MOUNTAINS) {
		noise_mount_height->perlinMap2D(node_min.X, node_min.Z);
	}

	if (spflags & MGV7_FLOATLANDS) {
		noise_floatland_base->perlinMap2D(node_min.X, node_min.Z);
		noise_float_base_height->perlinMap2D(node_min.X, node_min.Z);
	}

	//// Place nodes
	const v3s16 &em = vm->m_area.getExtent();
	s16 stone_surface_max_y = -MAX_MAP_GENERATION_LIMIT;
	u32 index2d = 0;

	for (s16 z = node_min.Z; z <= node_max.Z; z++)
	for (s16 x = node_min.X; x <= node_max.X; x++, index2d++) {
		s16 surface_y = baseTerrainLevelFromMap(index2d);
		if (surface_y > stone_surface_max_y)
			stone_surface_max_y = surface_y;

		// Get extent of floatland base terrain
		// '+1' to avoid a layer of stone at y = MAX_MAP_GENERATION_LIMIT
		s16 float_base_min = MAX_MAP_GENERATION_LIMIT + 1;
		s16 float_base_max = MAX_MAP_GENERATION_LIMIT;
		if (spflags & MGV7_FLOATLANDS)
			floatBaseExtentFromMap(&float_base_min, &float_base_max, index2d);

		u32 vi = vm->m_area.index(x, node_min.Y - 1, z);
		u32 index3d = (z - node_min.Z) * zstride_1u1d + (x - node_min.X);

		for (s16 y = node_min.Y - 1; y <= node_max.Y + 1;
				y++,
				index3d += ystride,
				VoxelArea::add_y(em, vi, 1)) {
			if (vm->m_data[vi].getContent() != CONTENT_IGNORE)
				continue;

			if (y <= surface_y) {
				vm->m_data[vi] = n_stone; // Base terrain
			} else if ((spflags & MGV7_MOUNTAINS) &&
					getMountainTerrainFromMap(index3d, index2d, y)) {
				vm->m_data[vi] = n_stone; // Mountain terrain
				if (y > stone_surface_max_y)
					stone_surface_max_y = y;
			} else if ((spflags & MGV7_FLOATLANDS) &&
					((y >= float_base_min && y <= float_base_max) ||
					getFloatlandMountainFromMap(index3d, index2d, y))) {
				vm->m_data[vi] = n_stone; // Floatland terrain
				stone_surface_max_y = node_max.Y;
			} else if (y <= water_level) {
				vm->m_data[vi] = n_water; // Ground level water
			} else if ((spflags & MGV7_FLOATLANDS) &&
					(y >= float_base_max && y <= floatland_level)) {
				vm->m_data[vi] = n_water; // Floatland water
			} else {
				vm->m_data[vi] = n_air;
			}
		}
	}

	return stone_surface_max_y;
}


void MapgenV7::generateRidgeTerrain()
{
	if (node_max.Y < water_level - 16 ||
			((spflags & MGV7_FLOATLANDS) && node_max.Y > shadow_limit))
		return;

	noise_ridge->perlinMap3D(node_min.X, node_min.Y - 1, node_min.Z);
	noise_ridge_uwater->perlinMap2D(node_min.X, node_min.Z);

	MapNode n_water(c_water_source);
	MapNode n_air(CONTENT_AIR);
	u32 index3d = 0;
	float width = 0.2f;

	for (s16 z = node_min.Z; z <= node_max.Z; z++)
	for (s16 y = node_min.Y - 1; y <= node_max.Y + 1; y++) {
		u32 vi = vm->m_area.index(node_min.X, y, z);
		for (s16 x = node_min.X; x <= node_max.X; x++, index3d++, vi++) {
			u32 index2d = (z - node_min.Z) * csize.X + (x - node_min.X);
			float uwatern = noise_ridge_uwater->result[index2d] * 2.0f;
			if (std::fabs(uwatern) > width)
				continue;
			// Optimises, but also avoids removing nodes placed by mods in
			// 'on-generated', when generating outside mapchunk.
			content_t c = vm->m_data[vi].getContent();
			if (c != c_stone)
				continue;

			float altitude = y - water_level;
			float height_mod = (altitude + 17.0f) / 2.5f;
			float width_mod = width - std::fabs(uwatern);
			float nridge = noise_ridge->result[index3d] *
				std::fmax(altitude, 0.0f) / 7.0f;
			if (nridge + width_mod * height_mod < 0.6f)
				continue;

			vm->m_data[vi] = (y > water_level) ? n_air : n_water;
		}
	}
}