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Name

snapfold - fold a thin disk N-body snapshot file into a cone along Z axis

Synopsis

snapfold in=snap-file out=snap-file [parameter=value] ...

Description

snapfold folds the positions and velocities of an N-body snapshot file representing a thin disk. The disk can be folded up to a cone around the +Z axis, or down to a cone around the -Z axis. Fold angle (theta=) must thus be between -90 and +90.

Parameters

The following parameters are recognized; they may be given in any order.
in=snap-file
Input data is read from snap-file, which must be in snapshot format.
out=snap-file
Output data is written to snap-file.
theta=x-angle
Fold Angle (in degrees). Default: 0.0
select=
Select the vectors for rotation. Normally you want to select all vectors. [pos,vel,acc]
fill=t|f
Fill the cone? Otherwise it will be a thin wall. Default: false
view=0,1,-1
Limit the view of the cone. view=0 shows the whole cone, view=1 shows the front side (towards the -Y axis) view=-1 the backside (towards the +Y axis). The value of 1+|view| will actually determine the opening angle in the plane of the visible part. [0]

Examples

Here is an example creating a tilted cone with outflow 
  set nbody = 10000
  set vscale = 0
  set outflow = 1.0
  set cone = 30
  set inc = 30
here vscale controls how much rotation is left, and outflow how much radial outflow. cone is the opening angle of the outflow, which points to the observer, but inc will incline it from the sky/disk plane. 
  mkdisk - $nbody mass=1 |\
    snapscale - - vscale=$vscale |\
    snapspin - - omega=$outflow outflow=t|\
    snapfold - - theta=90-$cone |\
    snaprotate - - $inc y |\
    snapgrid - $out.vel moment=-1
In this example the outflow is perpendicular to a disk, which is not in this example. A more expaned version is in the script mk_cone.

See Also

snaprotate(1NEMO) , snapspin(1NEMO) , snapshot(5NEMO)

Author

Peter Teuben

Files


$NEMO/src/nbody/trans/snapfill.c
$NEMO/scripts/csh/mk_cone - expanded example of a disk with one or two outflow
cones

History


20-nov-2017    V0.1 a quick hack to make a cone (at ESO)    PJT
22-mar-2018    V0.3 add fill=    PJT
22-jul-2020    note the new mk_cone script    PJT
28-jul-2020    V0.4 allow the cone to shrink in angle as well (view=)        PJT

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