OTTD Perlin Noise Landscape Generator, aka TerraGenesis Perlin. More...

#include "stdafx.h"
#include "clear_map.h"
#include "void_map.h"
#include "genworld.h"
#include "core/random_func.hpp"
#include "landscape_type.h"
#include "safeguards.h"

Data Structures
struct	HeightMap
	Height map - allocated array of heights (MapSizeX() + 1) x (MapSizeY() + 1) More...

Macros
#define	I2H(i) ((i) << height_decimal_bits)
	Conversion: int to Height.

#define	H2I(i) ((i) >> height_decimal_bits)
	Conversion: Height to int.

#define	A2I(i) ((i) >> amplitude_decimal_bits)
	Conversion: Amplitude to int.

#define	A2H(a) ((a) >> (amplitude_decimal_bits - height_decimal_bits))
	Conversion: Amplitude to Height.

#define	F(fraction) ((Height)(fraction * mh))

Typedefs
using	Height = int16_t
	Fixed point type for heights.

using	Amplitude = int
	Fixed point array for amplitudes (and percent values)

Functions
static Height	TGPGetMaxHeight ()
	Gets the maximum allowed height while generating a map based on mapsize, terraintype, and the maximum height level. More...

uint	GetEstimationTGPMapHeight ()
	Get an overestimation of the highest peak TGP wants to generate.

static Amplitude	GetAmplitude (int frequency)
	Get the amplitude associated with the currently selected smoothness and maximum height level. More...

static bool	IsValidXY (int x, int y)
	Check if a X/Y set are within the map. More...

static bool	AllocHeightMap ()
	Allocate array of (MapSizeX()+1)*(MapSizeY()+1) heights and init the _height_map structure members. More...

static void	FreeHeightMap ()
	Free height map.

static Height	RandomHeight (Amplitude rMax)
	Generates new random height in given amplitude (generated numbers will range from - amplitude to + amplitude) More...

static void	HeightMapGenerate ()
	Base Perlin noise generator - fills height map with raw Perlin noise. More...

static void	HeightMapGetMinMaxAvg (Height min_ptr, Height max_ptr, Height *avg_ptr)
	Returns min, max and average height from height map.

static int *	HeightMapMakeHistogram (Height h_min, [[maybe_unused]] Height h_max, int *hist_buf)
	Dill histogram and return pointer to its base point - to the count of zero heights.

static void	HeightMapSineTransform (Height h_min, Height h_max)
	Applies sine wave redistribution onto height map.

static void	HeightMapCurves (uint level)
	Additional map variety is provided by applying different curve maps to different parts of the map. More...

static void	HeightMapAdjustWaterLevel (Amplitude water_percent, Height h_max_new)
	Adjusts heights in height map to contain required amount of water tiles.

static double	perlin_coast_noise_2D (const double x, const double y, const double p, const int prime)
	This is a similar function to the main perlin noise calculation, but uses the value p passed as a parameter rather than selected from the predefined sequences. More...

static void	HeightMapCoastLines (uint8_t water_borders)
	This routine sculpts in from the edge a random amount, again a Perlin sequence, to avoid the rigid flat-edge slopes that were present before. More...

static void	HeightMapSmoothCoastInDirection (int org_x, int org_y, int dir_x, int dir_y)
	Start at given point, move in given direction, find and Smooth coast in that direction.

static void	HeightMapSmoothCoasts (uint8_t water_borders)
	Smooth coasts by modulating height of tiles close to map edges with cosine of distance from edge.

static void	HeightMapSmoothSlopes (Height dh_max)
	This routine provides the essential cleanup necessary before OTTD can display the terrain. More...

static void	HeightMapNormalize ()
	Height map terraform post processing: More...

static double	int_noise (const long x, const long y, const int prime)
	The Perlin Noise calculation using large primes The initial number is adjusted by two values; the generation_seed, and the passed parameter; prime. More...

static double	linear_interpolate (const double a, const double b, const double x)
	This routine determines the interpolated value between a and b.

static double	interpolated_noise (const double x, const double y, const int prime)
	This routine returns the smoothed interpolated noise for an x and y, using the values from the surrounding positions.

static void	TgenSetTileHeight (TileIndex tile, int height)
	A small helper function to initialize the terrain.

void	GenerateTerrainPerlin ()
	The main new land generator using Perlin noise. More...

Variables
static const int	height_decimal_bits = 4

static const int	amplitude_decimal_bits = 10

static HeightMap	_height_map = { {}, 0, 0, 0 }
	Global height map instance.

static const int	MAX_TGP_FREQUENCIES = 10
	Maximum number of TGP noise frequencies.

static const Amplitude	_water_percent [4] = {70, 170, 270, 420}
	Desired water percentage (100% == 1024) - indexed by _settings_game.difficulty.quantity_sea_lakes.

Detailed Description

OTTD Perlin Noise Landscape Generator, aka TerraGenesis Perlin.

Definition in file tgp.cpp.

Function Documentation

◆ AllocHeightMap()

static bool AllocHeightMap ( )

inlinestatic

Allocate array of (MapSizeX()+1)*(MapSizeY()+1) heights and init the _height_map structure members.

Returns: true on success

Definition at line 318 of file tgp.cpp.

References _height_map, Map::SizeX(), and Map::SizeY().

Referenced by GenerateTerrainPerlin().

◆ GenerateTerrainPerlin()

void GenerateTerrainPerlin ( )

The main new land generator using Perlin noise.

Desert landscape is handled different to all others to give a desert valley between two high mountains. Clearly if a low height terrain (flat/very flat) is chosen, then the tropic areas won't be high enough, and there will be very little tropic on the map. Thus Tropic works best on Hilly or Mountainous.

Definition at line 976 of file tgp.cpp.

References _settings_game, AllocHeightMap(), GameSettings::construction, ConstructionSettings::freeform_edges, FreeHeightMap(), GenerateWorldSetAbortCallback(), GWP_LANDSCAPE, HeightMapGenerate(), HeightMapNormalize(), and IncreaseGeneratingWorldProgress().

◆ GetAmplitude()

static Amplitude GetAmplitude ( int frequency )

static

Get the amplitude associated with the currently selected smoothness and maximum height level.

Parameters

frequency The frequency to get the amplitudes for

Returns: The amplitudes to apply to the map.

< Very smooth

< Smooth

< Rough

< Very rough

Definition at line 261 of file tgp.cpp.

References _settings_game, Clamp(), GameSettings::game_creation, I2H, MAX_TGP_FREQUENCIES, GameCreationSettings::tgen_smoothness, and TGPGetMaxHeight().

Referenced by HeightMapGenerate().

◆ HeightMapCoastLines()

static void HeightMapCoastLines ( uint8_t water_borders )

static

This routine sculpts in from the edge a random amount, again a Perlin sequence, to avoid the rigid flat-edge slopes that were present before.

The Perlin noise map doesn't know where we are going to slice across, and so we often cut straight through high terrain. The smoothing routine makes it legal, gradually increasing up from the edge to the original terrain height. By cutting parts of this away, it gives a far more irregular edge to the map-edge. Sometimes it works beautifully with the existing sea & lakes, and creates a very realistic coastline. Other times the variation is less, and the map-edge shows its cliff-like roots.

This routine may be extended to randomly sculpt the height of the terrain near the edge. This will have the coast edge at low level (1-3), rising in smoothed steps inland to about 15 tiles in. This should make it look as though the map has been built for the map size, rather than a slice through a larger map.

Please note that all the small numbers; 53, 101, 167, etc. are small primes to help give the perlin noise a bit more of a random feel.

Definition at line 721 of file tgp.cpp.

References _settings_game, GameSettings::game_creation, GameCreationSettings::map_x, and GameCreationSettings::map_y.

◆ HeightMapCurves()

static void HeightMapCurves ( uint level )

static

Additional map variety is provided by applying different curve maps to different parts of the map.

A randomized low resolution grid contains which curve map to use on each part of the make. This filtered non-linearly to smooth out transitions between curves, so each tile could have between 100% of one map applied or 25% of four maps.

The curve maps define different land styles, i.e. lakes, low-lands, hills and mountain ranges, although these are dependent on the landscape style chosen as well.

The level parameter dictates the resolution of the grid. A low resolution grid will result in larger continuous areas of a land style, a higher resolution grid splits the style into smaller areas.

Parameters

level Rough indication of the size of the grid sections to style. Small level means large grid sections.

Basically scale height X to height Y. Everything in between is interpolated.

< The height to scale from.

< The height to scale to.

Definition at line 544 of file tgp.cpp.

References I2H, and TGPGetMaxHeight().

◆ HeightMapGenerate()

static void HeightMapGenerate ( )

static

Base Perlin noise generator - fills height map with raw Perlin noise.

This runs several iterations with increasing precision; the last iteration looks at areas of 1 by 1 tiles, the second to last at 2 by 2 tiles and the initial 2**MAX_TGP_FREQUENCIES by 2**MAX_TGP_FREQUENCIES tiles.

Definition at line 357 of file tgp.cpp.

References _height_map, GetAmplitude(), Map::LogX(), Map::LogY(), and MAX_TGP_FREQUENCIES.

Referenced by GenerateTerrainPerlin().

◆ HeightMapNormalize()

static void HeightMapNormalize ( )

static

Height map terraform post processing:

water level adjusting
coast Smoothing
slope Smoothing
height histogram redistribution by sine wave transform

Definition at line 859 of file tgp.cpp.

References _settings_game, _water_percent, GameSettings::construction, GameCreationSettings::custom_sea_level, CUSTOM_SEA_LEVEL_NUMBER_DIFFICULTY, GameSettings::difficulty, ConstructionSettings::freeform_edges, GameSettings::game_creation, HeightMapAdjustWaterLevel(), DifficultySettings::quantity_sea_lakes, GameCreationSettings::tgen_smoothness, TGPGetMaxHeight(), and GameCreationSettings::water_borders.

Referenced by GenerateTerrainPerlin().

◆ HeightMapSmoothSlopes()

static void HeightMapSmoothSlopes ( Height dh_max )

static

This routine provides the essential cleanup necessary before OTTD can display the terrain.

When generated, the terrain heights can jump more than one level between tiles. This routine smooths out those differences so that the most it can change is one level. When OTTD can support cliffs, this routine may not be necessary.

Definition at line 836 of file tgp.cpp.

◆ int_noise()

static double int_noise	(	const long	x,
		const long	y,
		const int	prime
	)

static

The Perlin Noise calculation using large primes The initial number is adjusted by two values; the generation_seed, and the passed parameter; prime.

prime is used to allow the perlin noise generator to create useful random numbers from slightly different series.

Definition at line 893 of file tgp.cpp.

◆ IsValidXY()

static bool IsValidXY	(	int	x,
		int	y
	)

inlinestatic

Check if a X/Y set are within the map.

Parameters

x	coordinate x
y	coordinate y

Returns: true if within the map

Definition at line 308 of file tgp.cpp.

◆ perlin_coast_noise_2D()

static double perlin_coast_noise_2D	(	const double	x,
		const double	y,
		const double	p,
		const int	prime
	)

static

This is a similar function to the main perlin noise calculation, but uses the value p passed as a parameter rather than selected from the predefined sequences.

as you can guess by its title, i use this to create the indented coastline, which is just another perlin sequence.

Definition at line 943 of file tgp.cpp.

◆ RandomHeight()

static Height RandomHeight ( Amplitude rMax )

inlinestatic

Generates new random height in given amplitude (generated numbers will range from - amplitude to + amplitude)

Parameters

rMax	Limit of result

Returns: generated height

Definition at line 344 of file tgp.cpp.

References A2H, and RandomRange().

◆ TGPGetMaxHeight()

static Height TGPGetMaxHeight ( )

static

Gets the maximum allowed height while generating a map based on mapsize, terraintype, and the maximum height level.

Returns: The maximum height for the map generation.

Note: Values should never be lower than 3 since the minimum snowline height is 2.

Desired maximum height - indexed by:

_settings_game.difficulty.terrain_type
min(Map::LogX(), Map::LogY()) - MIN_MAP_SIZE_BITS

It is indexed by map size as well as terrain type since the map size limits the height of a usable mountain. For example, on a 64x64 map a 24 high single peak mountain (as if you raised land 24 times in the center of the map) will leave only a ring of about 10 tiles around the mountain to build on. On a 4096x4096 map, it won't cover any major part of the map.

< Very flat

< Flat

< Hilly

< Mountainous

< Alpinist

Definition at line 208 of file tgp.cpp.

References _settings_game, GameSettings::construction, GameCreationSettings::custom_terrain_type, CUSTOM_TERRAIN_TYPE_NUMBER_DIFFICULTY, GameSettings::difficulty, GameSettings::game_creation, I2H, Map::LogX(), Map::LogY(), ConstructionSettings::map_height_limit, MAX_MAP_SIZE_BITS, MIN_MAP_SIZE_BITS, and DifficultySettings::terrain_type.

Referenced by GetAmplitude(), GetEstimationTGPMapHeight(), HeightMapCurves(), and HeightMapNormalize().

Data Structures

Macros

Typedefs

Functions

Variables

Detailed Description

Function Documentation

◆ AllocHeightMap()

◆ GenerateTerrainPerlin()

◆ GetAmplitude()

◆ HeightMapCoastLines()

◆ HeightMapCurves()

◆ HeightMapGenerate()

◆ HeightMapNormalize()

◆ HeightMapSmoothSlopes()

◆ int_noise()

◆ IsValidXY()

◆ perlin_coast_noise_2D()

◆ RandomHeight()

◆ TGPGetMaxHeight()