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add support for more than one constraint for a single deformable node

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This commit is contained in:
Xuchen Han
2019-07-11 10:14:58 -07:00
parent b7e512a5f9
commit b28f1fdac3
4 changed files with 96 additions and 9 deletions
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4
src/BulletSoftBody/btBackwardEulerObjective.cpp
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@@ -8,7 +8,7 @@
#include "btBackwardEulerObjective.h"
btBackwardEulerObjective::btBackwardEulerObjective(btAlignedObjectArray<btSoftBody *>& softBodies, const TVStack& backup_v)
: cg(20)
: cg(50)
, m_softBodies(softBodies)
, precondition(DefaultPreconditioner())
, projection(m_softBodies, m_dt)
@@ -66,7 +66,7 @@ void btBackwardEulerObjective::computeStep(TVStack& dv, const TVStack& residual,
m_dt = dt;
btScalar tolerance = std::numeric_limits<float>::epsilon()* 16 * computeNorm(residual);
cg.solve(*this, dv, residual, tolerance);
}
}
void btBackwardEulerObjective::updateVelocity(const TVStack& dv)
{

3
src/BulletSoftBody/btCGProjection.h
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@@ -23,6 +23,8 @@ public:
std::unordered_map<btSoftBody::Node *, size_t> m_indices;
TVArrayStack m_constrainedDirections;
TArrayStack m_constrainedValues;
btAlignedObjectArray<int> m_constrainedId;
const btScalar& m_dt;
btCGProjection(btAlignedObjectArray<btSoftBody *>& softBodies, const btScalar& dt)
@@ -56,6 +58,7 @@ public:
m_constrainedDirections[i].clear();
m_constrainedValues[i].clear();
}
m_constrainedId.clear();
}
void updateId()

56
src/BulletSoftBody/btContactProjection.cpp
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@@ -114,6 +114,7 @@ void btContactProjection::setConstraintDirections()
m_constrainedValues[counter].push_back(0);
m_constrainedValues[counter].push_back(0);
m_constrainedValues[counter].push_back(0);
m_constrainedId.push_back(counter);
}
++counter;
}
@@ -180,10 +181,65 @@ void btContactProjection::setConstraintDirections()
++j;
m_constrainedDirections[m_indices[c.m_node]].push_back(cti.m_normal);
m_constrainedValues[m_indices[c.m_node]].resize(m_constrainedValues[m_indices[c.m_node]].size()+1);
m_constrainedId.push_back(m_indices[c.m_node]);
continue;
}
}
psb->m_rcontacts.removeAtIndex(j);
}
}
// for particles with more than three constrained directions, prune constrained directions so that there are at most three constrained directions
counter = 0;
const int dim = 3;
for (int i = 0; i < m_softBodies.size(); ++i)
{
const btSoftBody* psb = m_softBodies[i];
for (int j = 0; j < psb->m_nodes.size(); ++j)
{
if (m_constrainedDirections[counter].size() > dim)
{
btAlignedObjectArray<btVector3> prunedConstraints;
// always keep the first constrained direction
prunedConstraints.push_back(m_constrainedDirections[counter][0]);
// find the direction most orthogonal to the first direction and keep it
size_t selected = 1;
btScalar min_dotProductAbs = std::abs(prunedConstraints[0].dot(m_constrainedDirections[counter][selected]));
for (int j = 2; j < m_constrainedDirections[counter].size(); ++j)
{
btScalar dotProductAbs =std::abs(prunedConstraints[0].dot(m_constrainedDirections[counter][j]));
if (dotProductAbs < min_dotProductAbs)
{
selected = j;
min_dotProductAbs = dotProductAbs;
}
}
if (std::abs(min_dotProductAbs-1) < SIMD_EPSILON)
{
m_constrainedDirections[counter++] = prunedConstraints;
continue;
}
prunedConstraints.push_back(m_constrainedDirections[counter][selected]);
// find the direction most orthogonal to the previous two directions and keep it
size_t selected2 = (selected == 1) ? 2 : 1;
btVector3 normal = btCross(prunedConstraints[0], prunedConstraints[1]);
normal.normalize();
btScalar max_dotProductAbs = std::abs(normal.dot(m_constrainedDirections[counter][selected2]));
for (int j = 3; j < m_constrainedDirections[counter].size(); ++j)
{
btScalar dotProductAbs = std::abs(normal.dot(m_constrainedDirections[counter][j]));
if (dotProductAbs > min_dotProductAbs)
{
selected2 = j;
max_dotProductAbs = dotProductAbs;
}
}
prunedConstraints.push_back(m_constrainedDirections[counter][selected2]);
m_constrainedDirections[counter] = prunedConstraints;
m_constrainedValues[counter].resize(dim);
}
++counter;
}
}
}

32
src/BulletSoftBody/btContactProjection.h
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@@ -29,18 +29,37 @@ public:
// apply the constraints
virtual void operator()(TVStack& x)
{
for (int i = 0; i < x.size(); ++i)
const int dim = 3;
for (int j = 0; j < m_constrainedId.size(); ++j)
{
int i = m_constrainedId[j];
btAssert(m_constrainedDirections[i].size() <= dim);
if (m_constrainedDirections[i].size() <= 1)
{
for (int j = 0; j < m_constrainedDirections[i].size(); ++j)
{
x[i] -= x[i].dot(m_constrainedDirections[i][j]) * m_constrainedDirections[i][j];
}
}
else if (m_constrainedDirections[i].size() == 2)
{
btVector3 free_dir = btCross(m_constrainedDirections[i][0], m_constrainedDirections[i][1]);
free_dir.normalize();
x[i] = x[i].dot(free_dir) * free_dir;
}
else
x[i].setZero();
}
}
virtual void enforceConstraint(TVStack& x)
{
for (int i = 0; i < x.size(); ++i)
const int dim = 3;
for (int j = 0; j < m_constrainedId.size(); ++j)
{
int i = m_constrainedId[j];
btAssert(m_constrainedDirections[i].size() <= dim);
if (m_constrainedDirections[i].size() <= 1)
{
for (int j = 0; j < m_constrainedDirections[i].size(); ++j)
{
@@ -48,6 +67,15 @@ public:
x[i] += m_constrainedValues[i][j] * m_constrainedDirections[i][j];
}
}
else if (m_constrainedDirections[i].size() == 2)
{
btVector3 free_dir = btCross(m_constrainedDirections[i][0], m_constrainedDirections[i][1]);
free_dir.normalize();
x[i] = x[i].dot(free_dir) * free_dir + m_constrainedDirections[i][0] * m_constrainedValues[i][0] + m_constrainedDirections[i][1] * m_constrainedValues[i][1];
}
else
x[i] = m_constrainedDirections[i][0] * m_constrainedValues[i][0] + m_constrainedDirections[i][1] * m_constrainedValues[i][1] + m_constrainedDirections[i][2] * m_constrainedValues[i][2];
}
}
// update the constraints