//----------------------------------------------------------------------------
void Rope::CreateSprings ()
{
const int numParticles = 8;
const float step = 0.1f;
Vector3f gravity(0.0f, 0.0f, -1.0f);
Vector3f wind(0.0f, -0.25f, 0.0f);
float windChangeAmplitude = 0.01f;
float viscosity = 10.0f;
mModule = new0 PhysicsModule(numParticles, step, gravity, wind,
windChangeAmplitude, viscosity);
// Constant mass at interior points (endpoints are immovable).
mModule->SetMass(0, Mathf::MAX_REAL);
mModule->SetMass(numParticles - 1, Mathf::MAX_REAL);
int i;
for (i = 1; i < numParticles - 1; ++i)
{
mModule->SetMass(i, 1.0f);
}
// Initial position on a horizontal line segment.
float factor = 1.0f/(float)(numParticles - 1);
for (i = 0; i < numParticles; ++i)
{
mModule->Position(i) = Vector3f(i*factor, 0.0f, 1.0f);
}
// Initial velocities are all zero.
for (i = 0; i < numParticles; ++i)
{
mModule->Velocity(i) = Vector3f::ZERO;
}
// Springs are at rest in the initial horizontal configuration.
int numSprings = numParticles - 1;
float restLength = 1.0f/(float)numSprings;
for (i = 0; i < numSprings; ++i)
{
mModule->Constant(i) = 10.0f;
mModule->Length(i) = restLength;
}
}
//----------------------------------------------------------------------------
void GelatinCube::CreateSprings ()
{
// The inner 4-by-4-by-4 particles are used as the control points of a
// B-spline volume. The outer layer of particles are immovable to
// prevent the cuboid from collapsing into itself.
int numSlices = 6;
int numRows = 6;
int numCols = 6;
// Viscous forces applied. If you set viscosity to zero, the cuboid
// wiggles indefinitely since there is no dissipation of energy. If
// the viscosity is set to a positive value, the oscillations eventually
// stop. The length of time to steady state is inversely proportional
// to the viscosity.
#ifdef _DEBUG
float step = 0.1f;
#else
float step = 0.01f; // simulation needs to run slower in release mode
#endif
float viscosity = 0.01f;
mModule = new0 PhysicsModule(numSlices, numRows, numCols, step,
viscosity);
// The initial cuboid is axis-aligned. The outer shell is immovable.
// All other masses are constant.
float sFactor = 1.0f/(float)(numSlices - 1);
float rFactor = 1.0f/(float)(numRows - 1);
float cFactor = 1.0f/(float)(numCols - 1);
int s, r, c;
for (s = 0; s < numSlices; ++s)
{
for (r = 0; r < numRows; ++r)
{
for (c = 0; c < numCols; ++c)
{
mModule->Position(s, r, c) =
Vector3f(c*cFactor, r*rFactor, s*sFactor);
if (1 <= s && s < numSlices - 1
&& 1 <= r && r < numRows - 1
&& 1 <= c && c < numCols - 1)
{
mModule->SetMass(s, r, c, 1.0f);
mModule->Velocity(s, r, c) = 0.1f*Vector3f(
Mathf::SymmetricRandom(), Mathf::SymmetricRandom(),
Mathf::SymmetricRandom());
}
else
{
mModule->SetMass(s, r, c, Mathf::MAX_REAL);
mModule->Velocity(s, r, c) = Vector3f::ZERO;
}
}
}
}
// Springs are at rest in the initial configuration.
const float constant = 10.0f;
Vector3f diff;
for (s = 0; s < numSlices - 1; ++s)
{
for (r = 0; r < numRows; ++r)
{
for (c = 0; c < numCols; ++c)
{
mModule->ConstantS(s, r, c) = constant;
diff = mModule->Position(s + 1, r, c) -
mModule->Position(s, r, c);
mModule->LengthS(s, r, c) = diff.Length();
}
}
}
for (s = 0; s < numSlices; ++s)
{
for (r = 0; r < numRows - 1; ++r)
{
for (c = 0; c < numCols; ++c)
{
mModule->ConstantR(s, r, c) = constant;
diff = mModule->Position(s, r + 1, c) -
mModule->Position(s, r, c);
mModule->LengthR(s, r, c) = diff.Length();
}
}
}
for (s = 0; s < numSlices; ++s)
{
for (r = 0; r < numRows; ++r)
{
for (c = 0; c < numCols - 1; ++c)
{
mModule->ConstantC(s, r, c) = constant;
diff = mModule->Position(s, r, c + 1) -
mModule->Position(s, r, c);
mModule->LengthC(s, r, c) = diff.Length();
}
}
}
}