public vec3D[] ForcesBrute()
{
vec3D[] forces = new vec3D[bodyList.Count()];
for (int i = 0; i < forces.Length; i++)
{
forces[i] = new vec3D(0f, 0f, 0f);
}
for (int i = 0; i < bodyList.Count(); i++)
{
for (int j = 0; j < bodyList.Count(); j++)
{
if (i != j)
{
vec3D temp = forcePair(bodyList[i], bodyList[j]);
forces[i] += temp;
//forces[j] -= temp;
}
}
}
return(forces);
}
public vec3D[] forcesBHTree()
{
vec3D[] forces = new vec3D[bodyList.Count()];
for (int i = 0; i < bodyList.Count(); i++)
{
//Console.WriteLine("body nr: " + i);
forces[i] = forceTreeNode(rootNode, bodyList[i]);
//Console.WriteLine("force: " + forces[i].xCoord + " " + forces[i].yCoord);
}
return(forces);
}
/*
* public vec3D forcePair(Particle a, Particle b)
* {
* vec3D temp = new vec3D(0, 0, 0);
* vec3D r = a.pos - b.pos;
* float off = 0.01f;
*
* if (r.squared() > 0)
* temp = -1.0f * ((a.mass * b.mass) / (float)Math.Pow(r.squared() + off * off, 3 / 2)) * (r * (float)(1.0f / Math.Pow(r.squared(), 1.0f / 2.0f)) );
*
* //temp = -1 * (((a.mass * b.mass) / (Math.Pow((r.magnitude() + 1, 2)) * (a.pos - b.pos).magnitude()) * r);
* //Console.WriteLine("temp: " + temp.xCoord + " " + temp.yCoord + " " + temp.zCoord);
*
* return temp;
* }
*/
public vec3D forcePair(Particle a, Particle b)
{
vec3D temp = new vec3D(0, 0, 0);
vec3D r = a.pos - b.pos;
float eps = 1f;
if (Math.Sqrt(r.squared()) > 1f)
{
temp = -1.0f * ((a.mass * b.mass) / (float)Math.Pow(r.squared() + eps * eps, 2 / 2)) * (r * (float)(1.0f / Math.Pow(r.squared(), 1.0 / 2.0)));
}
//temp = -1 * (((a.mass * b.mass) / (Math.Pow((r.magnitude() + 1, 2)) * (a.pos - b.pos).magnitude()) * r);
//Console.WriteLine("temp: " + temp.xCoord + " " + temp.yCoord + " " + temp.zCoord);
return(temp);
}
static void RunSim(int numBodies, string initMethod, string forceMethod, string intMethod, float deltaT, int numFrames)
{
Frame firstFrame = new Frame(100);
float velocity = (float)Math.Sqrt((Math.Pow(10, 10) * 2 + 0) / (2f * 50));
vec3D velvec = new vec3D(0f, (float)(velocity), 0f);
firstFrame.AddBodies(numBodies, initMethod, new vec3D(0, 0, 0), new vec3D(0, 0, 0));
//firstFrame.AddBodies(125, initMethod, new vec3D(-50, 0, 0), velvec * 0.6f);
//firstFrame.AddBodies(1, initMethod, new vec3D(0, 0, 0), new vec3D(0, 0, 0));
//firstFrame.AddBodies(125, initMethod, new vec3D(50, 0, 0), velvec * -0.6f);
//for (int i = 0; i < firstFrame.bodyList.Count; i++)
// firstFrame.bodyList[i].vel *= 1f;
Simulation simulation = new Simulation(firstFrame);
simulation.WriteToFile();
int frameCounter = 0;
if (intMethod == "Beeman")
{
simulation.NextStep(deltaT, forceMethod, "Euler");
simulation.WriteToFile();
simulation.NextStep(deltaT, forceMethod, "Euler");
simulation.WriteToFile();
}
for (int i = 0; i < numFrames; i++)
{
Console.WriteLine(frameCounter);
frameCounter++;
simulation.NextStep(deltaT, forceMethod, intMethod);
simulation.WriteToFile();
}
simulation.writer.Close();
}
public vec3D forceTreeNode(TreeNode node, Particle part)
{
float theta = node.q.edgeLength / (float)Math.Sqrt((node.body.pos - part.pos).squared());
//Console.WriteLine("theta: " + theta);
if (!((node.body.pos - part.pos).squared() == 0))
{
if (theta < 1f)
{
return(forcePair(part, node.body));
}
else
{
if (node.children.Count() > 0)
{
//Console.WriteLine("int node");
vec3D force = new vec3D(0, 0, 0);
for (int i = 0; i < 8; i++)
{
force += forceTreeNode(node.children[i], part);
}
return(force);
}
else
{
//Console.WriteLine("ext node");
return(forcePair(part, node.body));
}
}
}
else
{
//Console.WriteLine("zero vec");
return(new vec3D(0, 0, 0));
}
}
public oct(vec3D LowLeftCorner, float edgeLength)
{
this.LowLeftCorner = LowLeftCorner;
this.edgeLength = edgeLength;
}
public void NextStep(float deltaT, string forceMethod, string integrationMethod)
{
vec3D[] newForces = new vec3D[lastFrame.bodyList.Count()];
Frame newFrame = new Frame(lastFrame);
Frame oldFrame = new Frame(lastFrame);
switch (forceMethod)
{
case ("Brute"):
{
if (integrationMethod != "Beeman")
{
newForces = lastFrame.ForcesBrute();
for (int i = 0; i < oldFrame.bodyList.Count; i++)
{
prevLastForces[i] = lastForces[i];
lastForces[i] = newForces[i];
}
}
break;
}
case ("BarnesHut"):
{
lastFrame.BuildTree();
newForces = lastFrame.forcesBHTree();
for (int i = 0; i < oldFrame.bodyList.Count; i++)
{
prevLastForces[i] = lastForces[i];
lastForces[i] = newForces[i];
}
break;
}
}
switch (integrationMethod)
{
case ("Euler"):
{
for (int i = 0; i < oldFrame.bodyList.Count; i++)
{
newFrame.bodyList[i].pos += deltaT * oldFrame.bodyList[i].vel;
newFrame.bodyList[i].vel += (deltaT / oldFrame.bodyList[i].mass) * newForces[i];
}
//frameList.Add(newFrame);
lastFrame = new Frame(newFrame);
prevLastFrame = new Frame(oldFrame);
break;
}
case ("Beeman"):
{
//vec3D[] newForces = new vec3D[lastFrame.bodyList.Count()];
for (int i = 0; i < oldFrame.bodyList.Count; i++)
{
newFrame.bodyList[i].pos += deltaT * oldFrame.bodyList[i].vel + (deltaT * deltaT / oldFrame.bodyList[i].mass) * ((2f / 3f) * lastForces[i] - (1f / 6f) * prevLastForces[i]);
}
newFrame.BuildTree();
newForces = newFrame.forcesBHTree();
//newForces = newFrame.ForcesBrute();
for (int i = 0; i < oldFrame.bodyList.Count; i++)
{
prevLastForces[i] = lastForces[i];
lastForces[i] = newForces[i];
}
for (int i = 0; i < oldFrame.bodyList.Count; i++)
{
//vec3D diff = (5f / 12f) * newForces[i] + (2f / 3f) * lastForces[i] - (1 / 12) * prevLastForces[i];
//Console.WriteLine("diff: " + diff.xCoord + " " + diff.yCoord + " " + diff.zCoord);
newFrame.bodyList[i].vel += (deltaT / oldFrame.bodyList[i].mass) * ((5f / 12f) * newForces[i] + (2f / 3f) * lastForces[i] - (1f / 12f) * prevLastForces[i]);
}
lastFrame = new Frame(newFrame);
prevLastFrame = new Frame(oldFrame);
break;
}
}
}
public void AddBodies(int nBodies, string method, vec3D CenterOfMass = null, vec3D CenterVelocity = null)
{
switch (method)
{
case ("Random"):
for (int i = 0; i < nBodies; i++)
{
bodyList.Add(new Particle(new vec3D((float)randomGenerator.NextDouble() * 2f * length - length, (float)randomGenerator.NextDouble() * 2f * length - length, (float)randomGenerator.NextDouble() * 2f * length - length), new vec3D(0, 0, 0), 1));
}
break;
case ("UniformSphere"):
double rad;
double r;
for (int i = 0; i < nBodies; i++)
{
r = randomGenerator.NextDouble() * length;
rad = randomGenerator.NextDouble() * 2 * Math.PI;
vec3D posvec = new vec3D((float)(r * Math.Cos(rad)), (float)(r * Math.Sin(rad)), 0f);
vec3D velvec = new vec3D((float)(1 * r * Math.Sin(rad)), (float)(-1 * r * Math.Cos(rad)), 0f);
bodyList.Add(new Particle(posvec, velvec, 1));
}
break;
case ("Plummer"):
{
for (int i = 0; i < nBodies; i++)
{
float radius = (float)(1.0 / Math.Sqrt(Math.Pow(randomGenerator.NextDouble(), (-2.0 / 3.0)) - 1.0));
float theta = (float)(Math.Acos(randomGenerator.NextDouble() * 2.0 - 1.0));
float phi = (float)(randomGenerator.NextDouble() * 2.0 * Math.PI);
vec3D posvec = new vec3D((float)(radius * Math.Sin(theta) * Math.Cos(phi)), (float)(radius * Math.Sin(theta) * Math.Sin(phi)), (float)(radius * Math.Cos(theta)));
posvec += CenterOfMass;
float x = 0f;
float y = 0.1f;
while (y > x * x * (float)Math.Pow((1 - x * x), 3.5))
{
x = (float)randomGenerator.NextDouble();
y = (float)randomGenerator.NextDouble() * 0.1f;
}
double velocity = x * Math.Sqrt(2) * Math.Pow((1 + radius * radius), -0.25);
//Console.WriteLine(velocity);
theta = (float)(Math.Acos(randomGenerator.NextDouble() * 2 - 1));
phi = (float)(randomGenerator.NextDouble() * 2 * Math.PI);
vec3D velvec = new vec3D((float)(velocity * Math.Sin(theta) * Math.Cos(phi)), (float)(velocity * Math.Sin(theta) * Math.Sin(phi)), (float)(velocity * Math.Cos(theta)));
velvec += CenterVelocity;
bodyList.Add(new Particle(posvec, velvec, 1 / (float)nBodies));
}
break;
}
case ("Kuzmin"):
{
bodyList.Add(new Particle(new vec3D(0, 0, 0), new vec3D(0, 0, 0), 10));
for (int i = 0; i < nBodies; i++)
{
float rand = (float)randomGenerator.NextDouble();
float a = 0.01f;
float radius = (float)Math.Sqrt((a * a) / (Math.Pow(1 - rand, 2)) + a * a);
float phi = (float)(randomGenerator.NextDouble() * 2.0 * Math.PI);
vec3D posvec = new vec3D((float)(radius * Math.Cos(phi)), (float)(radius * Math.Sin(phi)), (float)randomGenerator.NextDouble());
//float velocity = (float)Math.Sqrt((1 - (a) / (Math.Sqrt(a * a + radius * radius))) / (radius * radius));
//float velocity = radius * (float)Math.Pow(radius * radius + a * a, 3/4);
float velocity = (float)Math.Sqrt(10 / radius);
//Console.WriteLine(velocity);
vec3D velvec = new vec3D((float)(velocity * Math.Sin(phi)), (float)(-1 * velocity * Math.Cos(phi)), 0);
//bodyList.Add(new Particle(posvec, velvec, 1 / (float)nBodies));
//bodyList.Add(new Particle(posvec, new vec3D(0,0,0), 1 / (float)nBodies));
bodyList.Add(new Particle(posvec, velvec, 1f));
//bodyList.Add(new Particle(posvec, 0.5f * velvec , 0.00025f));
}
break;
}
case ("Kepler"):
{
float blackHoleMass = (float)Math.Pow(10, 10);
bodyList.Add(new Particle(CenterOfMass, CenterVelocity, blackHoleMass));
for (int i = 0; i < nBodies; i++)
{
float radius = (float)(randomGenerator.NextDouble() * 35) + 10f;
float phi = (float)(randomGenerator.NextDouble() * 2.0 * Math.PI);
vec3D posvec = new vec3D((float)(radius * Math.Cos(phi)), (float)(radius * Math.Sin(phi)), 0f);
float velocity = (float)Math.Sqrt(blackHoleMass / radius);
vec3D velvec = new vec3D((float)(velocity * Math.Sin(phi)), (float)(-1f * velocity * Math.Cos(phi)), 0f);
posvec += CenterOfMass;
velvec += CenterVelocity;
bodyList.Add(new Particle(posvec, velvec, 1f));
}
break;
}
}
}
public Particle(vec3D pos, vec3D vel, float mass)
{
this.pos = pos;
this.vel = vel;
this.mass = mass;
}
