# compute smd/tlsph/shape command

## Syntax

    compute ID group-ID smd/tlsph/shape

-   ID, group-ID are documented in [compute](compute) command
-   smd/tlsph/shape = style name of this compute command

## Examples

``` LAMMPS
compute 1 all smd/tlsph/shape
```

## Description

Define a computation that outputs the current shape of the volume
associated with a particle as a rotated ellipsoid. It is only meaningful
for particles which interact according to the Total-Lagrangian SPH pair
style.

See [this PDF guide](PDF/MACHDYN_LAMMPS_userguide.pdf)\_ to use Smooth
Mach Dynamics in LAMMPS.

## Output info

This compute calculates a per-particle vector of vectors, which can be
accessed by any command that uses per-particle values from a compute as
input. See the [Howto output](Howto_output) page for an overview of
LAMMPS output options.

The per-particle vector has 7 entries. The first three entries
correspond to the lengths of the ellipsoid\'s axes and have units of
length. These axis values are computed as the contact radius times the
xx, yy, or zz components of the Green-Lagrange strain tensor associated
with the particle. The next 4 values are quaternions (order: q, x, y, z)
which describe the spatial rotation of the particle relative to its
initial state.

## Restrictions

This compute is part of the MACHDYN package. It is only enabled if
LAMMPS was built with that package. See the [Build
package](Build_package) page for more info.

This quantity will be computed only for particles which interact with
the Total-Lagrangian SPH pair style.

## Related commands

[smd/contact/radius](compute_smd_contact_radius)

## Default

none