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diff --git a/OpenSim/Region/Terrain.BasicTerrain/libTerrainBSD/Channel/Manipulators/NavierStokes.cs b/OpenSim/Region/Terrain.BasicTerrain/libTerrainBSD/Channel/Manipulators/NavierStokes.cs
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--- a/OpenSim/Region/Terrain.BasicTerrain/libTerrainBSD/Channel/Manipulators/NavierStokes.cs
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1/*
2 * Copyright (c) Contributors, http://opensimulator.org/
3 * See CONTRIBUTORS.TXT for a full list of copyright holders.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 * * Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * * Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * * Neither the name of the OpenSim Project nor the
13 * names of its contributors may be used to endorse or promote products
14 * derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
17 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
20 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
21 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
22 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
23 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
25 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28namespace libTerrain
29{
30 partial class Channel
31 {
32 // Navier Stokes Algorithms ported from
33 // "Real-Time Fluid Dynamics for Games" by Jos Stam.
34 // presented at GDC 2003.
35
36 // Poorly ported from C++. (I gave up making it properly native somewhere after nsSetBnd)
37
38 private static int nsIX(int i, int j, int N)
39 {
40 return ((i) + (N + 2)*(j));
41 }
42
43// TODO: unused
44// private static void nsSwap(ref double x0, ref double x)
45// {
46// double tmp = x0;
47// x0 = x;
48// x = tmp;
49// }
50
51 private static void nsSwap(ref double[] x0, ref double[] x)
52 {
53 double[] tmp = x0;
54 x0 = x;
55 x = tmp;
56 }
57
58 private void nsAddSource(int N, ref double[] x, ref double[] s, double dt)
59 {
60 int i;
61 int size = (N + 2)*(N + 2);
62 for (i = 0; i < size; i++)
63 {
64 x[i] += dt*s[i];
65 }
66 }
67
68 private void nsSetBnd(int N, int b, ref double[] x)
69 {
70 int i;
71 for (i = 0; i <= N; i++)
72 {
73 x[nsIX(0, i, N)] = b == 1 ? -x[nsIX(1, i, N)] : x[nsIX(1, i, N)];
74 x[nsIX(0, N + 1, N)] = b == 1 ? -x[nsIX(N, i, N)] : x[nsIX(N, i, N)];
75 x[nsIX(i, 0, N)] = b == 2 ? -x[nsIX(i, 1, N)] : x[nsIX(i, 1, N)];
76 x[nsIX(i, N + 1, N)] = b == 2 ? -x[nsIX(i, N, N)] : x[nsIX(i, N, N)];
77 }
78 x[nsIX(0, 0, N)] = 0.5f*(x[nsIX(1, 0, N)] + x[nsIX(0, 1, N)]);
79 x[nsIX(0, N + 1, N)] = 0.5f*(x[nsIX(1, N + 1, N)] + x[nsIX(0, N, N)]);
80 x[nsIX(N + 1, 0, N)] = 0.5f*(x[nsIX(N, 0, N)] + x[nsIX(N + 1, 1, N)]);
81 x[nsIX(N + 1, N + 1, N)] = 0.5f*(x[nsIX(N, N + 1, N)] + x[nsIX(N + 1, N, N)]);
82 }
83
84 private void nsLinSolve(int N, int b, ref double[] x, ref double[] x0, double a, double c)
85 {
86 int i, j;
87 for (i = 1; i <= N; i++)
88 {
89 for (j = 1; j <= N; j++)
90 {
91 x[nsIX(i, j, N)] = (x0[nsIX(i, j, N)] + a*
92 (x[nsIX(i - 1, j, N)] +
93 x[nsIX(i + 1, j, N)] +
94 x[nsIX(i, j - 1, N)] + x[nsIX(i, j + 1, N)])
95 )/c;
96 }
97 }
98
99 nsSetBnd(N, b, ref x);
100 }
101
102 private void nsDiffuse(int N, int b, ref double[] x, ref double[] x0, double diff, double dt)
103 {
104 double a = dt*diff*N*N;
105 nsLinSolve(N, b, ref x, ref x0, a, 1 + 4*a);
106 }
107
108 private void nsAdvect(int N, int b, ref double[] d, ref double[] d0, ref double[] u, ref double[] v, double dt)
109 {
110 int i, j, i0, j0, i1, j1;
111 double x, y, s0, t0, s1, t1, dt0;
112
113 dt0 = dt*N;
114
115 for (i = 1; i <= N; i++)
116 {
117 for (j = 1; j <= N; j++)
118 {
119 x = i - dt0*u[nsIX(i, j, N)];
120 y = j - dt0*v[nsIX(i, j, N)];
121
122 if (x < 0.5)
123 x = 0.5;
124 if (x > N + 0.5)
125 x = N + 0.5;
126 i0 = (int) x;
127 i1 = i0 + 1;
128
129 if (y < 0.5)
130 y = 0.5;
131 if (y > N + 0.5)
132 y = N + 0.5;
133 j0 = (int) y;
134 j1 = j0 + 1;
135
136 s1 = x - i0;
137 s0 = 1 - s1;
138 t1 = y - j0;
139 t0 = 1 - t1;
140
141 d[nsIX(i, j, N)] = s0*(t0*d0[nsIX(i0, j0, N)] + t1*d0[nsIX(i0, j1, N)]) +
142 s1*(t0*d0[nsIX(i1, j0, N)] + t1*d0[nsIX(i1, j1, N)]);
143 }
144 }
145
146 nsSetBnd(N, b, ref d);
147 }
148
149 public void nsProject(int N, ref double[] u, ref double[] v, ref double[] p, ref double[] div)
150 {
151 int i, j;
152
153 for (i = 1; i <= N; i++)
154 {
155 for (j = 1; j <= N; j++)
156 {
157 div[nsIX(i, j, N)] = -0.5*
158 (u[nsIX(i + 1, j, N)] - u[nsIX(i - 1, j, N)] + v[nsIX(i, j + 1, N)] -
159 v[nsIX(i, j - 1, N)])/N;
160 p[nsIX(i, j, N)] = 0;
161 }
162 }
163
164 nsSetBnd(N, 0, ref div);
165 nsSetBnd(N, 0, ref p);
166
167 nsLinSolve(N, 0, ref p, ref div, 1, 4);
168
169 for (i = 1; i <= N; i++)
170 {
171 for (j = 1; j <= N; j++)
172 {
173 u[nsIX(i, j, N)] -= 0.5*N*(p[nsIX(i + 1, j, N)] - p[nsIX(i - 1, j, N)]);
174 v[nsIX(i, j, N)] -= 0.5*N*(p[nsIX(i, j + 1, N)] - p[nsIX(i, j - 1, N)]);
175 }
176 }
177
178 nsSetBnd(N, 1, ref u);
179 nsSetBnd(N, 2, ref v);
180 }
181
182 private void nsDensStep(int N, ref double[] x, ref double[] x0, ref double[] u, ref double[] v, double diff,
183 double dt)
184 {
185 nsAddSource(N, ref x, ref x0, dt);
186 nsSwap(ref x0, ref x);
187 nsDiffuse(N, 0, ref x, ref x0, diff, dt);
188 nsSwap(ref x0, ref x);
189 nsAdvect(N, 0, ref x, ref x0, ref u, ref v, dt);
190 }
191
192 private void nsVelStep(int N, ref double[] u, ref double[] v, ref double[] u0, ref double[] v0, double visc,
193 double dt)
194 {
195 nsAddSource(N, ref u, ref u0, dt);
196 nsAddSource(N, ref v, ref v0, dt);
197 nsSwap(ref u0, ref u);
198 nsDiffuse(N, 1, ref u, ref u0, visc, dt);
199 nsSwap(ref v0, ref v);
200 nsDiffuse(N, 2, ref v, ref v0, visc, dt);
201 nsProject(N, ref u, ref v, ref u0, ref v0);
202 nsSwap(ref u0, ref u);
203 nsSwap(ref v0, ref v);
204 nsAdvect(N, 1, ref u, ref u0, ref u0, ref v0, dt);
205 nsAdvect(N, 2, ref v, ref v0, ref u0, ref v0, dt);
206 nsProject(N, ref u, ref v, ref u0, ref v0);
207 }
208
209 private void nsBufferToDoubles(ref double[] dens, int N, ref double[,] doubles)
210 {
211 int i;
212 int j;
213
214 for (i = 1; i <= N; i++)
215 {
216 for (j = 1; j <= N; j++)
217 {
218 doubles[i - 1, j - 1] = dens[nsIX(i, j, N)];
219 }
220 }
221 }
222
223 private void nsDoublesToBuffer(double[,] doubles, int N, ref double[] dens)
224 {
225 int i;
226 int j;
227
228 for (i = 1; i <= N; i++)
229 {
230 for (j = 1; j <= N; j++)
231 {
232 dens[nsIX(i, j, N)] = doubles[i - 1, j - 1];
233 }
234 }
235 }
236
237 private void nsSimulate(int N, int rounds, double dt, double diff, double visc)
238 {
239 int size = (N*2)*(N*2);
240
241 double[] u = new double[size]; // Force, X axis
242 double[] v = new double[size]; // Force, Y axis
243 double[] u_prev = new double[size];
244 double[] v_prev = new double[size];
245 double[] dens = new double[size];
246 double[] dens_prev = new double[size];
247
248 nsDoublesToBuffer(map, N, ref dens);
249 nsDoublesToBuffer(map, N, ref dens_prev);
250
251 for (int i = 0; i < rounds; i++)
252 {
253 u_prev = u;
254 v_prev = v;
255 dens_prev = dens;
256
257 nsVelStep(N, ref u, ref v, ref u_prev, ref v_prev, visc, dt);
258 nsDensStep(N, ref dens, ref dens_prev, ref u, ref v, diff, dt);
259 }
260
261 nsBufferToDoubles(ref dens, N, ref map);
262 }
263
264 /// <summary>
265 /// Performs computational fluid dynamics on a channel
266 /// </summary>
267 /// <param name="rounds">The number of steps to perform (Recommended: 20)</param>
268 /// <param name="dt">Delta Time - The time between steps (Recommended: 0.1)</param>
269 /// <param name="diff">Fluid diffusion rate (Recommended: 0.0)</param>
270 /// <param name="visc">Fluid viscosity (Recommended: 0.0)</param>
271 public void navierStokes(int rounds, double dt, double diff, double visc)
272 {
273 nsSimulate(h, rounds, dt, diff, visc);
274 }
275
276 public void navierStokes(int rounds, double dt, double diff, double visc, ref double[,] uret, ref double[,] vret)
277 {
278 int N = h;
279
280 int size = (N*2)*(N*2);
281
282 double[] u = new double[size]; // Force, X axis
283 double[] v = new double[size]; // Force, Y axis
284 double[] u_prev = new double[size];
285 double[] v_prev = new double[size];
286 double[] dens = new double[size];
287 double[] dens_prev = new double[size];
288
289 nsDoublesToBuffer(map, N, ref dens);
290 nsDoublesToBuffer(map, N, ref dens_prev);
291
292 for (int i = 0; i < rounds; i++)
293 {
294 u_prev = u;
295 v_prev = v;
296 dens_prev = dens;
297
298 nsVelStep(N, ref u, ref v, ref u_prev, ref v_prev, visc, dt);
299 nsDensStep(N, ref dens, ref dens_prev, ref u, ref v, diff, dt);
300 }
301
302 nsBufferToDoubles(ref u, N, ref uret);
303 nsBufferToDoubles(ref v, N, ref vret);
304 nsBufferToDoubles(ref dens, N, ref map);
305 }
306 }
307}
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