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/*
* Copyright (c) Contributors, http://opensimulator.org/
* See CONTRIBUTORS.TXT for a full list of copyright holders.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the OpenSim Project nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
using System;
namespace libTerrain
{
partial class Channel
{
// Ideas for Aerobic erosion
//
// Unlike thermal (gravity) and hydraulic (water suspension)
// aerobic erosion should displace mass by moving sediment
// in "hops". The length of the hop being dictated by the
// presence of sharp cliffs and wind speed.
// The ability to pickup sediment is defined by the total
// surface area, such that:
// 0 0 0
// 0 1 0
// 0 0 0
// Would be the best possible value for sediment to be
// picked up (total difference = 8) and flatter land
// will erode less quickly.
// Suspended particles assist the erosion process by hitting
// the surface and chiselling additional particles off faster
// than alone.
// Particles are deposited when one of two conditions is met
// First:
// When particles hit a wall - such that the
// wind direction points at a difference >= the
// deposition mininum talus.
// Second:
// When wind speed is lowered to below the minimum
// required for transit. An idea for this is to
// use the navier-stokes algorithms for simulating
// pressure across the terrain.
/// <summary>
/// An experimental erosion algorithm developed by Adam. Moves sediment by factoring the surface area of each height point.
/// </summary>
/// <param name="windspeed">0..1 The speed of the wind</param>
/// <param name="pickup_talus_minimum">The minimum angle at which rock is eroded 0..1 (recommended: <= 0.30)</param>
/// <param name="drop_talus_minimum">The minimum angle at which rock is dropped 0..1 (recommended: >= 0.00)</param>
/// <param name="carry">The percentage of rock which can be picked up to pickup 0..1</param>
/// <param name="rounds">The number of erosion rounds (recommended: 25+)</param>
/// <param name="lowest">Drop sediment at the lowest point?</param>
public void AerobicErosion(double windspeed, double pickupTalusMinimum, double dropTalusMinimum, double carry,
int rounds, bool lowest, bool usingFluidDynamics)
{
bool debugImages = false;
Channel wind = new Channel(w, h);
Channel sediment = new Channel(w, h);
int x, y, i, j;
Normalise();
wind = Copy();
wind.Noise();
if (debugImages)
wind.SaveImage("testimg/wind_start.png");
if (usingFluidDynamics)
{
wind.navierStokes(20, 0.1, 0.0, 0.0);
}
else
{
wind.Pertubation(30);
}
if (debugImages)
wind.SaveImage("testimg/wind_begin.png");
for (i = 0; i < rounds; i++)
{
// Convert some rocks to sand
for (x = 1; x < w - 1; x++)
{
for (y = 1; y < h - 1; y++)
{
double me = Get(x, y);
double surfacearea = 0.3; // Everything will erode even if it's flat. Just slower.
for (j = 0; j < 9; j++)
{
int[] coords = Neighbours(NeighbourSystem.Moore, j);
double target = Get(x + coords[0], y + coords[1]);
surfacearea += Math.Abs(target - me);
}
double amount = surfacearea*wind.map[x, y]*carry;
if (amount < 0)
amount = 0;
if (surfacearea > pickupTalusMinimum)
{
Set(x, y, map[x, y] - amount);
sediment.map[x, y] += amount;
}
}
}
if (usingFluidDynamics)
{
sediment.navierStokes(7, 0.1, 0.0, 0.1);
Channel noiseChan = new Channel(w, h);
noiseChan.Noise();
wind.Blend(noiseChan, 0.01);
wind.navierStokes(10, 0.1, 0.01, 0.01);
sediment.Distort(wind, windspeed);
}
else
{
wind.Pertubation(15); // Can do better later
wind.seed++;
sediment.Pertubation(10); // Sediment is blown around a bit
sediment.seed++;
}
if (debugImages)
wind.SaveImage("testimg/wind_" + i.ToString() + ".png");
// Convert some sand to rock
for (x = 1; x < w - 1; x++)
{
for (y = 1; y < h - 1; y++)
{
double me = Get(x, y);
double surfacearea = 0.01; // Flat land does not get deposition
double min = double.MaxValue;
int[] minside = new int[2];
for (j = 0; j < 9; j++)
{
int[] coords = Neighbours(NeighbourSystem.Moore, j);
double target = Get(x + coords[0], y + coords[1]);
surfacearea += Math.Abs(target - me);
if (target < min && lowest)
{
minside = (int[]) coords.Clone();
min = target;
}
}
double amount = surfacearea*(1.0 - wind.map[x, y])*carry;
if (amount < 0)
amount = 0;
if (surfacearea > dropTalusMinimum)
{
Set(x + minside[0], y + minside[1], map[x + minside[0], y + minside[1]] + amount);
sediment.map[x, y] -= amount;
}
}
}
if (debugImages)
sediment.SaveImage("testimg/sediment_" + i.ToString() + ".png");
wind.Normalise();
wind *= windspeed;
Normalise();
}
Channel myself = this;
myself += sediment;
myself.Normalise();
if (debugImages)
SaveImage("testimg/output.png");
}
}
}
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