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Add another wind model, that doesn't clamp the maximum force.

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Thanks to saggitasaggita for the patch, see http://code.google.com/p/bullet/issues/detail?id=532
This commit is contained in:
erwin.coumans
2011-09-01 01:53:45 +00:00
parent 822e8a3383
commit 06112592fd
3 changed files with 147 additions and 45 deletions
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124
src/BulletSoftBody/btSoftBody.cpp
View File

@@ -2701,35 +2701,51 @@ void btSoftBody::applyForces()
/* Aerodynamics */
if(as_vaero)
{
const btVector3 rel_v = n.m_v - medium.m_velocity;
const btVector3 rel_v = n.m_v - medium.m_velocity;
const btScalar rel_v_len = rel_v.length();
const btScalar rel_v2 = rel_v.length2();
if(rel_v2>SIMD_EPSILON)
{
btVector3 nrm = n.m_n;
/* Setup normal */
switch(m_cfg.aeromodel)
const btVector3 rel_v_nrm = rel_v.normalized();
btVector3 nrm = n.m_n;
if (m_cfg.aeromodel == btSoftBody::eAeroModel::V_TwoSidedLiftDrag)
{
case btSoftBody::eAeroModel::V_Point:
nrm = NormalizeAny(rel_v);
break;
case btSoftBody::eAeroModel::V_TwoSided:
nrm *= (btScalar)( (btDot(nrm,rel_v) < 0) ? -1 : +1);
break;
default:
{
}
btVector3 fDrag(0, 0, 0);
btVector3 fLift(0, 0, 0);
btScalar n_dot_v = nrm.dot(rel_v_nrm);
btScalar tri_area = 0.5f * n.m_area;
fDrag = 0.5f * kDG * medium.m_density * rel_v2 * tri_area * n_dot_v * (-rel_v_nrm);
// Check angle of attack
// cos(10<31>) = 0.98480
if ( 0 < n_dot_v && n_dot_v < 0.98480f)
fLift = 0.5f * kLF * medium.m_density * rel_v_len * tri_area * btSqrt(1.0f-n_dot_v*n_dot_v) * (nrm.cross(rel_v_nrm).cross(rel_v_nrm));
n.m_f += fDrag;
n.m_f += fLift;
}
const btScalar dvn = btDot(rel_v,nrm);
/* Compute forces */
if(dvn>0)
else if (m_cfg.aeromodel == btSoftBody::eAeroModel::V_Point || m_cfg.aeromodel == btSoftBody::eAeroModel::V_OneSided || m_cfg.aeromodel == btSoftBody::eAeroModel::V_TwoSided)
{
btVector3 force(0,0,0);
const btScalar c0 = n.m_area * dvn * rel_v2/2;
const btScalar c1 = c0 * medium.m_density;
force += nrm*(-c1*kLF);
force += rel_v.normalized() * (-c1 * kDG);
ApplyClampedForce(n, force, dt);
}
if (btSoftBody::eAeroModel::V_TwoSided)
nrm *= (btScalar)( (btDot(nrm,rel_v) < 0) ? -1 : +1);
const btScalar dvn = btDot(rel_v,nrm);
/* Compute forces */
if(dvn>0)
{
btVector3 force(0,0,0);
const btScalar c0 = n.m_area * dvn * rel_v2/2;
const btScalar c1 = c0 * medium.m_density;
force += nrm*(-c1*kLF);
force += rel_v.normalized() * (-c1 * kDG);
ApplyClampedForce(n, force, dt);
}
}
}
}
}
@@ -2754,31 +2770,63 @@ void btSoftBody::applyForces()
const btVector3 v=(f.m_n[0]->m_v+f.m_n[1]->m_v+f.m_n[2]->m_v)/3;
const btVector3 x=(f.m_n[0]->m_x+f.m_n[1]->m_x+f.m_n[2]->m_x)/3;
EvaluateMedium(m_worldInfo,x,medium);
medium.m_velocity = m_windVelocity;
medium.m_density = m_worldInfo->air_density;
const btVector3 rel_v=v-medium.m_velocity;
const btScalar rel_v_len = rel_v.length();
const btScalar rel_v2=rel_v.length2();
if(rel_v2>SIMD_EPSILON)
{
btVector3 nrm=f.m_normal;
/* Setup normal */
switch(m_cfg.aeromodel)
const btVector3 rel_v_nrm = rel_v.normalized();
btVector3 nrm = f.m_normal;
if (m_cfg.aeromodel == btSoftBody::eAeroModel::F_TwoSidedLiftDrag)
{
case btSoftBody::eAeroModel::F_TwoSided:
nrm*=(btScalar)(btDot(nrm,rel_v)<0?-1:+1);break;
default:
nrm *= (btScalar)( (btDot(nrm,rel_v) < 0) ? -1 : +1);
btVector3 fDrag(0, 0, 0);
btVector3 fLift(0, 0, 0);
btScalar n_dot_v = nrm.dot(rel_v_nrm);
btScalar tri_area = 0.5f * f.m_ra;
fDrag = 0.5f * kDG * medium.m_density * rel_v2 * tri_area * n_dot_v * (-rel_v_nrm);
// Check angle of attack
// cos(10<31>) = 0.98480
if ( 0 < n_dot_v && n_dot_v < 0.98480f)
fLift = 0.5f * kLF * medium.m_density * rel_v_len * tri_area * btSqrt(1.0f-n_dot_v*n_dot_v) * (nrm.cross(rel_v_nrm).cross(rel_v_nrm));
fDrag /= 3;
fLift /= 3;
for(int j=0;j<3;++j)
{
if (f.m_n[j]->m_im>0)
{
f.m_n[j]->m_f += fDrag;
f.m_n[j]->m_f += fLift;
}
}
}
const btScalar dvn=btDot(rel_v,nrm);
/* Compute forces */
if(dvn>0)
else if (m_cfg.aeromodel == btSoftBody::eAeroModel::F_OneSided || m_cfg.aeromodel == btSoftBody::eAeroModel::F_TwoSided)
{
btVector3 force(0,0,0);
const btScalar c0 = f.m_ra*dvn*rel_v2;
const btScalar c1 = c0*medium.m_density;
force += nrm*(-c1*kLF);
force += rel_v.normalized()*(-c1*kDG);
force /= 3;
for(int j=0;j<3;++j) ApplyClampedForce(*f.m_n[j],force,dt);
if (btSoftBody::eAeroModel::F_TwoSided)
nrm *= (btScalar)( (btDot(nrm,rel_v) < 0) ? -1 : +1);
const btScalar dvn=btDot(rel_v,nrm);
/* Compute forces */
if(dvn>0)
{
btVector3 force(0,0,0);
const btScalar c0 = f.m_ra*dvn*rel_v2;
const btScalar c1 = c0*medium.m_density;
force += nrm*(-c1*kLF);
force += rel_v.normalized()*(-c1*kDG);
force /= 3;
for(int j=0;j<3;++j) ApplyClampedForce(*f.m_n[j],force,dt);
}
}
}
}

12
src/BulletSoftBody/btSoftBody.h
View File

@@ -80,11 +80,13 @@ public:
///eAeroModel
struct eAeroModel { enum _ {
V_Point, ///Vertex normals are oriented toward velocity
V_TwoSided, ///Vertex normals are fliped to match velocity
V_OneSided, ///Vertex normals are taken as it is
F_TwoSided, ///Face normals are fliped to match velocity
F_OneSided, ///Face normals are taken as it is
V_Point, ///Vertex normals are oriented toward velocity
V_TwoSided, ///Vertex normals are flipped to match velocity
V_TwoSidedLiftDrag, ///Vertex normals are flipped to match velocity and lift and drag forces are applied
V_OneSided, ///Vertex normals are taken as it is
F_TwoSided, ///Face normals are flipped to match velocity
F_TwoSidedLiftDrag, ///Face normals are flipped to match velocity and lift and drag forces are applied
F_OneSided, ///Face normals are taken as it is
END
};};