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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@5992 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp
2011-04-21 20:05:45 +00:00
parent 0f41ccb943
commit 428bdd0b09
8 changed files with 48 additions and 15 deletions
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32
src/math_extra.cpp
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@ -428,8 +428,8 @@ void quat_to_mat_trans(const double *quat, double mat[3][3])
/* ----------------------------------------------------------------------
compute space-frame inertia tensor of an ellipsoid
quat = orientiation quaternion of ellipsoid
radii = 3 radii of ellipsoid
quat = orientiation quaternion of ellipsoid
return symmetric inertia tensor as 6-vector in Voigt notation
------------------------------------------------------------------------- */
@ -454,6 +454,36 @@ void inertia_ellipsoid(double *radii, double *quat, double mass,
inertia[5] = tensor[0][1];
}
/* ----------------------------------------------------------------------
compute space-frame inertia tensor of a line segment in 2d
length = length of line
theta = orientiation of line
return symmetric inertia tensor as 6-vector in Voigt notation
------------------------------------------------------------------------- */
void inertia_line(double length, double theta, double mass, double *inertia)
{
double p[3][3],ptrans[3][3],itemp[3][3],tensor[3][3];
double q[4],idiag[3];
q[0] = cos(0.5*theta);
q[1] = q[2] = 0.0;
q[3] = sin(0.5*theta);
MathExtra::quat_to_mat(q,p);
MathExtra::quat_to_mat_trans(q,ptrans);
idiag[0] = 0.0;
idiag[1] = 1.0/12.0 * mass * length*length;
idiag[2] = 1.0/12.0 * mass * length*length;
MathExtra::diag_times3(idiag,ptrans,itemp);
MathExtra::times3(p,itemp,tensor);
inertia[0] = tensor[0][0];
inertia[1] = tensor[1][1];
inertia[2] = tensor[2][2];
inertia[3] = tensor[1][2];
inertia[4] = tensor[0][2];
inertia[5] = tensor[0][1];
}
/* ----------------------------------------------------------------------
compute space-frame inertia tensor of a triangle
v0,v1,v2 = 3 vertices of triangle