public void Update()
{
if (immovable)
{
return;
}
double energy = v.Dot(v);
if (energy < 0.01)
{
if (aboutToFreeze)
{
//curGravity.Scale(0.8);
framesToFreeze++;
if (framesToFreeze > 20)
{
freezed = true;
aboutToFreeze = false;
v.Clear();
}
}
else
{
framesToFreeze = 0;
aboutToFreeze = true;
}
}
else
{
if (aboutToFreeze)
{
aboutToFreeze = false;
}
}
}
public void SimulateFast(double dt)
{
// Applying forces
// Run CD
Collide();
DateTime t = DateTime.Now;
if (joints.Count == 0 && contacts.Count == 0)
{
foreach (Particle p in particles)
{
p.Integrate(dt);
}
return;
}
uint n = (uint)particles.Count;
uint dofs = 0;
int i, j;
double idt = 1 / dt;
//for (i = 0, j = 0; i < n; i++)
// if (!particles[i].freezed)
// {
// dofs++;
// particles[i].id = j;
// j++;
// }
dofs = 2 * n;
// Then build mass matrix M
MatrixMN M = new MatrixMN(dofs, dofs);
for (i = 0, j = 0; i < n; i++)
{
//if (particles[i].freezed) continue;
double mass = particles[i].invMass;
if (particles[i].immovable)
{
mass = 0;
}
M.v[j][j] = mass;
M.v[j + 1][j + 1] = mass;
j += 2;
}
// Build external force vector, velocity vector, position vector
VectorN F = new VectorN(dofs);
VectorN V = new VectorN(dofs);
VectorN X = new VectorN(dofs);
for (i = 0, j = 0; i < n; i++)
{
//if (particles[i].freezed) continue;
F.v[j] = particles[i].forceAccum.v[0];
F.v[j + 1] = particles[i].forceAccum.v[1];
if (particles[i].immovable)
{
V.v[j] = 0;
V.v[j + 1] = 0;
}
else
{
V.v[j] = particles[i].v.v[0];
V.v[j + 1] = particles[i].v.v[1];
}
X.v[j] = particles[i].pos.v[0];
X.v[j + 1] = particles[i].pos.v[1];
j += 2;
}
// Build Jacobian J
uint s = (uint)(joints.Count + contacts.Count);
MatrixMN J = new MatrixMN(s, 4);
int[][] Jmap = new int[s][];
VectorN xi = new VectorN(s);
for (i = 0; i < joints.Count; i++)
{
VectorN Jpartial = joints[i].Jacobian();
J.v[i][0] = Jpartial.v[0];
J.v[i][1] = Jpartial.v[1];
J.v[i][2] = Jpartial.v[2];
J.v[i][3] = Jpartial.v[3];
Jmap[i] = new int[2];
Jmap[i][0] = 2 * joints[i].pair[0].id;
Jmap[i][1] = 2 * joints[i].pair[1].id;
xi.v[i] = Jpartial.v[4];
}
for (j = 0, i = joints.Count; j < contacts.Count; j++, i++)
{
VectorN Jpartial = contacts[j].Jacobian();
J.v[i][0] = Jpartial.v[0];
J.v[i][1] = Jpartial.v[1];
J.v[i][2] = Jpartial.v[2];
J.v[i][3] = Jpartial.v[3];
Jmap[i] = new int[2];
Jmap[i][0] = 2 * contacts[j].pair[0].id;
Jmap[i][1] = 2 * contacts[j].pair[1].id;
xi.v[i] = Jpartial.v[4];
}
// 1/dt * V - MF
VectorN q = new VectorN(dofs);
for (i = 0; i < dofs; i++)
{
q.v[i] = idt * V.v[i] - M.v[i][i] * F.v[i];
}
// b = 1 / dt * xi - Jq
VectorN b = new VectorN(s);
for (i = 0; i < s; i++)
{
int off1 = Jmap[i][0];
int off2 = Jmap[i][1];
b.v[i] = idt * xi.v[i] - (J.v[i][0] * q.v[off1] + J.v[i][1] * q.v[off1 + 1] +
J.v[i][2] * q.v[off2] + J.v[i][3] * q.v[off2 + 1]);
}
// A = M^-1 * J^T
MatrixMN A = new MatrixMN(4, s);
for (i = 0; i < s; i++)
{
int off1 = Jmap[i][0];
int off2 = Jmap[i][1];
A.v[0][i] = M.v[off1][off1] * J.v[i][0] + M.v[off1][off1 + 1] * J.v[i][1] + M.v[off1][off2] * J.v[i][2] + M.v[off1][off2 + 1] * J.v[i][3];
A.v[1][i] = M.v[off1 + 1][off1] * J.v[i][0] + M.v[off1 + 1][off1 + 1] * J.v[i][1] + M.v[off1 + 1][off2] * J.v[i][2] + M.v[off1 + 1][off2 + 1] * J.v[i][3];
A.v[2][i] = M.v[off2][off1] * J.v[i][0] + M.v[off2][off1 + 1] * J.v[i][1] + M.v[off2][off2] * J.v[i][2] + M.v[off2][off2 + 1] * J.v[i][3];
A.v[3][i] = M.v[off2 + 1][off1] * J.v[i][0] + M.v[off2 + 1][off1 + 1] * J.v[i][1] + M.v[off2 + 1][off2] * J.v[i][2] + M.v[off2 + 1][off2 + 1] * J.v[i][3];
}
// Up to here all is right
//MatrixMN Jfull = new MatrixMN(s, dofs);
//MatrixMN Afull = new MatrixMN(dofs, s);
//Jfull.Clear();
//Afull.Clear();
//for (i = 0; i < s; i++)
//{
// int off1 = Jmap[i][0];
// int off2 = Jmap[i][1];
// Jfull.v[i][off1] = J.v[i][0];
// Jfull.v[i][off1 + 1] = J.v[i][1];
// Jfull.v[i][off2] = J.v[i][2];
// Jfull.v[i][off2 + 1] = J.v[i][3];
// Afull.v[off1][i] = A.v[0][i];
// Afull.v[off1 + 1][i] = A.v[1][i];
// Afull.v[off2][i] = A.v[2][i];
// Afull.v[off2 + 1][i] = A.v[3][i];
//}
//MatrixMN Z = Jfull.Multiply(Afull);
//// Solve Ax = b
//VectorN lambda = MatrixMN.SolveGSSOR(Z, b);
//Jfull = Jfull.Transpose();
//F.Add(Jfull.Multiply(lambda));
// Apparently there're a few bugs here...
// Solve JAx = b
// PGS-SOR starts here
VectorN lambda = new VectorN(b);
// a = A * lambda
// diag - diagonal elements of JA
VectorN a = new VectorN(dofs);
VectorN diag = new VectorN(s);
a.Clear();
for (i = 0; i < s; i++)
{
int off1 = Jmap[i][0];
int off2 = Jmap[i][1];
a.v[off1] += A.v[0][i] * lambda.v[i];
a.v[off1 + 1] += A.v[1][i] * lambda.v[i];
a.v[off2] += A.v[2][i] * lambda.v[i];
a.v[off2 + 1] += A.v[3][i] * lambda.v[i];
diag.v[i] = 1 / (J.v[i][0] * A.v[0][i] + J.v[i][1] * A.v[1][i] + J.v[i][2] * A.v[2][i] + J.v[i][3] * A.v[3][i]);
}
for (int iter = 0; iter < 10; iter++)
{
for (i = 0; i < s; i++)
{
int off1 = Jmap[i][0];
int off2 = Jmap[i][1];
double l = b.v[i] - J.v[i][0] * a.v[off1] - J.v[i][1] * a.v[off1 + 1] - J.v[i][2] * a.v[off2] - J.v[i][3] * a.v[off2 + 1];
l *= diag.v[i];
double delta = lambda.v[i];
lambda.v[i] += 0.9 * (l - delta);
if (lambda.v[i] < 0)
{
lambda.v[i] = 0;
}
delta = lambda.v[i] - delta;
a.v[off1] += delta * A.v[0][i];
a.v[off1 + 1] += delta * A.v[1][i];
a.v[off2] += delta * A.v[2][i];
a.v[off2 + 1] += delta * A.v[3][i];
}
}
// F + J^T * lambda
for (i = 0; i < s; i++)
{
int off1 = Jmap[i][0];
int off2 = Jmap[i][1];
F.v[off1] += J.v[i][0] * lambda.v[i];
F.v[off1 + 1] += J.v[i][1] * lambda.v[i];
F.v[off2] += J.v[i][2] * lambda.v[i];
F.v[off2 + 1] += J.v[i][3] * lambda.v[i];
}
for (i = 0, j = 0; i < n; i++, j += 2)
{
particles[i].forceAccum.v[0] = F.v[j];
particles[i].forceAccum.v[1] = F.v[j + 1];
particles[i].v.v[0] = V.v[j];
particles[i].v.v[1] = V.v[j + 1];
particles[i].pos.v[0] = X.v[j];
particles[i].pos.v[1] = X.v[j + 1];
particles[i].Integrate(dt);
particles[i].forceAccum.Clear();
}
TimeSpan tt = DateTime.Now.Subtract(t);
solverTime = (double)(tt.TotalMilliseconds);// / (double)TimeSpan.TicksPerMillisecond;
}