It produces a fractal image from an N particle gravity simulation. Warning: The calculation takes about a minute!
Java, 162 lines
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 | // <applet code="GravityFr" width=500 height=500></applet>
// GravityFr.java (200810094) Fuat Bahadir
import java.applet.Applet;
import java.awt.*;
import java.awt.image.*;
public class GravityFr extends Applet
{
Image img;
int wd,ht,pix[],alpha;
public void init()
{
wd=getSize().width;ht=getSize().height;alpha=255;
pix=new int[wd*ht];
gr();
img=createImage(new MemoryImageSource(wd,ht,pix,0,wd));
}
public void paint(Graphics g)
{
g.drawImage(img,0,0,this);
// Refresh Periodically
long t=System.currentTimeMillis();
while((System.currentTimeMillis()-t)<10000) {;}
// delete the old graph
for(int i=0;i<wd*ht;++i) pix[i]=0;
gr();
img=createImage(new MemoryImageSource(wd,ht,pix,0,wd));
repaint();
}
/*
public void update(Graphics g) // to stop refresh flickering
{
paint(g);
}
*/
public void gr()
{
// fractal level
int level=100;
// number of gravity sources
int n = (int)(Math.random() * 6)+3;
double G = 1.0; // general gravity constant
double h = 0.0025; // time step (real solution; lim h->0)
double dmin = 10.0; // min allowed distance between objects
int mx, my, k, j, ix, iy;
mx = wd-1;my = ht-1;
double ang, v, dx, dy, d, a, ax, ay;
double x[], y[], xnew[], ynew[], m[], vx[], vy[];
double x0[], y0[], vx0[], vy0[];
m=new double[n];
x=new double[n];y=new double[n];
xnew=new double[n];ynew=new double[n];
vx=new double[n];vy=new double[n];
x0=new double[n];y0=new double[n];
vx0=new double[n];vy0=new double[n];
double Sx, Sy, Svx, Svy, Sm;
Sx = Sy = Svx = Svy = Sm = 0;
for(k=0;k<n;++k)
{
x[k] = (double)((Math.random()*2-1) * mx/2+mx/2);
y[k] = (double)((Math.random()*2-1) * my/2+my/2);
m[k] = (double)(Math.random() * 30) + 10;
m[k] = (m[k]*m[k]*m[k])*40;
ang = (double)(Math.random() * 2 * Math.PI);
v = (double)(Math.random() * 200);
vx[k] = (double)(v * Math.cos(ang));
vy[k] = (double)(v * Math.sin(ang));
Sx = Sx + m[k] * x[k];
Sy = Sy + m[k] * y[k];
Svx = Svx + m[k] * vx[k];
Svy = Svy + m[k] * vy[k];
Sm = Sm + m[k];
}
for (k = 0; k < n; k++)
{
x[k] = x[k] - (Sx / Sm) + (mx / 2.0);
y[k] = y[k] - (Sy / Sm) + (my / 2.0);
vx[k] = vx[k] - (Svx / Sm);
vy[k] = vy[k] - (Svy / Sm);
}
for (k = 0; k < n; k++)
{
x0[k] = x[k];
y0[k] = y[k];
vx0[k] = vx[k];
vy0[k] = vy[k];
}
// color palette
int rd[], gr[], bl[];
rd=new int[16];gr=new int[16];bl=new int[16];
for(k=0;k<16;k++)
{
rd[k] = (int)(Math.random() * 256);
gr[k] = (int)(Math.random() * 256);
bl[k] = (int)(Math.random() * 256);
}
//
for(iy=0;iy<my;iy++)
{
for(ix=0;ix<mx;ix++)
{
// load the initial values
for (k = 0; k < n; k++)
{
x[k] = x0[k];
y[k] = y0[k];
vx[k] = vx0[k];
vy[k] = vy0[k];
}
x[0]=ix;y[0]=iy;
for(int fr=0;fr<level;fr++)
{
// n-body simulation
for(k=0;k<n;++k)
{
ax = 0; ay = 0;
for(j=0;j<n;++j)
{
if(k!=j)
{
dx = x[j] - x[k]; dy = y[j] - y[k];
d = (double)Math.sqrt(dx * dx + dy * dy);
d = Math.max(dmin, d);
dx = dx / d; dy = dy / d;
a = G * m[j] / (d * d);
ax = ax + a * dx; ay = ay + a * dy;
}
}
xnew[k] = x[k] + vx[k] * h;
ynew[k] = y[k] + vy[k] * h;
vx[k] = vx[k] + ax * h; vy[k] = vy[k] + ay * h;
}
for(k=0;k<n;++k)
{
x[k] = xnew[k]; y[k] = ynew[k];
}
}
dx = x[0] - ix; dy = y[0] - iy;
d = (double)Math.sqrt(dx * dx + dy * dy);
pix[wd*iy+ix]=(alpha<<24)|(rd[((int)d*100)%16]<<16)|(gr[((int)d*100)%16]<<8)|bl[((int)d*100)%16];
}
}
}
}
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