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jMonkeyEngine is a 3-D game engine for adventurous Java developers
/*
* Copyright (c) 2009-2021 jMonkeyEngine
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*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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package com.jme3.terrain.heightmap;
import java.util.Random;
import java.util.logging.Logger;
/**
* FluidSimHeightMap generates a height map based using some
* sort of fluid simulation. The heightmap is treated as a highly viscous and
* rubbery fluid enabling to fine tune the generated heightmap using a number
* of parameters.
*
* @author Frederik Boelthoff
* @see Terrain Generation Using Fluid Simulation
* @version $Id$
*
*/
public class FluidSimHeightMap extends AbstractHeightMap {
private static final Logger logger = Logger.getLogger(FluidSimHeightMap.class.getName());
private float waveSpeed = 100.0f; // speed at which the waves travel
private float timeStep = 0.033f; // constant time-step between each iteration
private float nodeDistance = 10.0f; // distance between each node of the surface
private float viscosity = 100.0f; // viscosity of the fluid
private int iterations; // number of iterations
private float minInitialHeight = -500; // min initial height
private float maxInitialHeight = 500; // max initial height
private long seed; // the seed for the random number generator
float coefA, coefB, coefC; // pre-computed coefficients in the fluid equation
/**
* Constructor sets the attributes of the hill system and generates the
* height map. It gets passed a number of tweakable parameters which
* fine-tune the outcome.
*
* @param size
* size the size of the terrain to be generated
* @param iterations
* the number of iterations to do
* @param minInitialHeight
* the minimum initial height of a terrain value
* @param maxInitialHeight
* the maximum initial height of a terrain value
* @param viscosity
* the viscosity of the fluid
* @param waveSpeed
* the speed at which the waves travel
* @param timestep
* the constant time-step between each iteration
* @param nodeDistance
* the distance between each node of the heightmap
* @param seed
* the seed to generate the same heightmap again
* @throws Exception
* if size of the terrain is not greater than zero, or number of
* iterations is not greater that zero, or the minimum initial height
* is greater than the maximum (or the other way around)
*/
public FluidSimHeightMap(int size, int iterations, float minInitialHeight, float maxInitialHeight, float viscosity, float waveSpeed, float timestep, float nodeDistance, long seed) throws Exception {
if (size <= 0 || iterations <= 0 || minInitialHeight >= maxInitialHeight) {
throw new Exception(
"Either size of the terrain is not greater that zero, "
+ "or number of iterations is not greater that zero, "
+ "or minimum height greater or equal as the maximum, "
+ "or maximum height smaller or equal as the minimum.");
}
this.size = size;
this.seed = seed;
this.iterations = iterations;
this.minInitialHeight = minInitialHeight;
this.maxInitialHeight = maxInitialHeight;
this.viscosity = viscosity;
this.waveSpeed = waveSpeed;
this.timeStep = timestep;
this.nodeDistance = nodeDistance;
load();
}
/**
* Constructor sets the attributes of the hill system and generates the
* height map.
*
* @param size
* size the size of the terrain to be generated
* @param iterations
* the number of iterations to do
* @throws Exception
* if size of the terrain is not greater than zero, or number of
* iterations is not greater than zero
*/
public FluidSimHeightMap(int size, int iterations) throws Exception {
if (size <= 0 || iterations <= 0) {
throw new Exception(
"Either size of the terrain is not greater than zero, "
+ "or number of iterations is not greater than zero");
}
this.size = size;
this.iterations = iterations;
load();
}
/**
* Generates a heightmap using fluid simulation and the attributes set by
* the constructor or the setters.
*/
@Override
public boolean load() {
// Clean up data if needed.
if (null != heightData) {
unloadHeightMap();
}
heightData = new float[size * size];
float[][] tempBuffer = new float[2][size * size];
Random random = new Random(seed);
// pre-compute the coefficients in the fluid equation
coefA = (4 - (8 * waveSpeed * waveSpeed * timeStep * timeStep) / (nodeDistance * nodeDistance)) / (viscosity * timeStep + 2);
coefB = (viscosity * timeStep - 2) / (viscosity * timeStep + 2);
coefC = ((2 * waveSpeed * waveSpeed * timeStep * timeStep) / (nodeDistance * nodeDistance)) / (viscosity * timeStep + 2);
// initialize the heightmaps to random values except for the edges
for (int i = 0; i < size; i++) {
for (int j = 0; j < size; j++) {
tempBuffer[0][j + i * size] = tempBuffer[1][j + i * size] = randomRange(random, minInitialHeight, maxInitialHeight);
}
}
int curBuf = 0;
int ind;
float[] oldBuffer;
float[] newBuffer;
// Iterate over the heightmap, applying the fluid simulation equation.
// Although it requires knowledge of the two previous timesteps, it only
// accesses one pixel of the k-1 timestep, so using a simple trick we only
// need to store the heightmap twice, not three times, and we can avoid
// copying data every iteration.
for (int i = 0; i < iterations; i++) {
oldBuffer = tempBuffer[1 - curBuf];
newBuffer = tempBuffer[curBuf];
for (int y = 0; y < size; y++) {
for (int x = 0; x < size; x++) {
ind = x + y * size;
float neighborsValue = 0;
int neighbors = 0;
if (x > 0) {
neighborsValue += newBuffer[ind - 1];
neighbors++;
}
if (x < size - 1) {
neighborsValue += newBuffer[ind + 1];
neighbors++;
}
if (y > 0) {
neighborsValue += newBuffer[ind - size];
neighbors++;
}
if (y < size - 1) {
neighborsValue += newBuffer[ind + size];
neighbors++;
}
if (neighbors != 4) {
neighborsValue *= 4 / neighbors;
}
oldBuffer[ind] = coefA * newBuffer[ind] + coefB
* oldBuffer[ind] + coefC * (neighborsValue);
}
}
curBuf = 1 - curBuf;
}
// put the normalized heightmap into the range [0...255] and into the heightmap
for (int y = 0; y < size; y++) {
for (int x = 0; x < size; x++) {
heightData[x + y * size] = tempBuffer[curBuf][x + y * size];
}
}
normalizeTerrain(NORMALIZE_RANGE);
logger.fine("Created Heightmap using fluid simulation");
return true;
}
private float randomRange(Random random, float min, float max) {
return (random.nextFloat() * (max - min)) + min;
}
/**
* Sets the number of times the fluid simulation should be iterated over
* the heightmap. The more iterations, the fewer features (hills, etcetera)
* the terrain will have, and the smoother it will be.
*
* @param iterations
* the number of iterations to perform
* @throws Exception
* if iterations is not greater than zero
*/
public void setIterations(int iterations) throws Exception {
if (iterations <= 0) {
throw new Exception(
"Number of iterations is not greater than zero");
}
this.iterations = iterations;
}
/**
* Sets the maximum initial height of the terrain.
*
* @param maxInitialHeight
* the maximum initial height
* @see #setMinInitialHeight(float)
*/
public void setMaxInitialHeight(float maxInitialHeight) {
this.maxInitialHeight = maxInitialHeight;
}
/**
* Sets the minimum initial height of the terrain.
*
* @param minInitialHeight
* the minimum initial height
* @see #setMaxInitialHeight(float)
*/
public void setMinInitialHeight(float minInitialHeight) {
this.minInitialHeight = minInitialHeight;
}
/**
* Sets the distance between each node of the heightmap.
*
* @param nodeDistance
* the distance between each node
*/
public void setNodeDistance(float nodeDistance) {
this.nodeDistance = nodeDistance;
}
/**
* Sets the time-speed between each iteration of the fluid
* simulation algorithm.
*
* @param timeStep
* the time-step between each iteration
*/
public void setTimeStep(float timeStep) {
this.timeStep = timeStep;
}
/**
* Sets the viscosity of the simulated fluid.
*
* @param viscosity
* the viscosity of the fluid
*/
public void setViscosity(float viscosity) {
this.viscosity = viscosity;
}
/**
* Sets the speed at which the waves travel.
*
* @param waveSpeed
* the speed at which the waves travel
*/
public void setWaveSpeed(float waveSpeed) {
this.waveSpeed = waveSpeed;
}
}
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