.. _chap-vtk-output:

Visualization with VTK tools (e.g. Paraview or VisIt)
*****************************************************

Since 3-D models can be very hard to visualize, and since RADMC-3D is not
made for quick rendering, it can be very useful to make use of a number of
freely available 3-D rendering tools, for example:

* Paraview www.paraview.org
  
* VisIt visit.llnl.gov

RADMC-3D can create data files for use with these tools. The file format is
VTK (Visual Tool Kit), which is a simple ascii file format which is used by
various programs. Those tools are not only useful for visualizing the
3-D structure of the model, but also for visualizing the structure of the
grid which can be, when using AMR, rather complex. 

The file that RADMC-3D writes is called ``model.vtk``\ . You should be able to
open it directly from within e.g. paraview. Figures :numref:`fig-disk-with-vtk`
and :numref:`fig-modeljuhasz-with-vtk` gives an example of how you can analyze a
complex geometry with AMR refinement with Paraview. The file {\em always}
includes the information about the grid. In addition you can also make RADMC-3D
add scalar fields or vector fields.

To create a VTK file for viewing the grid only, type:
::

  radmc3d vtk_grid

To create a VTK file for viewing the gas density (this file then also
includes the grid of course) type:
::

  radmc3d vtk_gas_density

Since density can span a huge range, the 10-log of the density (in units of
gram/cm\ :math:`^3`) is written instead. For the gas temperature:
::

  radmc3d vtk_gas_temperature

which is written in Kelvin (and linearly, not log). For the dust density of
dust species 1:
::

  radmc3d vtk_dust_density 1

and for dust species 2:
::

  radmc3d vtk_dust_density 2

Also these densities are 10-log. RADMC-3D typically computes the dust
temperature using a Monte Carlo approach. By typing
::

  radmc3d vtk_dust_temperature 1

RADMC-3D will try to read the dust temperature from the file
``dust_temperature.dat`` (if this file has been created 
earlier by a ``radmc3d mctherm`` call) and then create
the VTK file. You can also let RADMC-3D compute the temperature
directly and write it out to VTK right afterward:
::

  radmc3d mctherm vtk_dust_temperature 1


If you are doing line transfer you may wish to visualize the number density
of the molecules (or atoms):
::

  radmc3d vtk_molspec 1

(for molecular species 1). This number density (in cm\ :math:`^{-3}`) is also
written in 10-log form.  You may also wish to visualize the polulations of
level 1 (ground state) of molecule 2:
::

  radmc3d vtk_levelpop 2 1

The gas velocity field can be written to VTK file by
::

  radmc3d vtk_velocity

This is a vector field.

Note: The VTK mode works for 3-D cartesian and 3-D spherical coordinates
(thanks, Attila Juhasz, for the 3-D spherical mode!).

.. _fig-disk-with-vtk:

.. figure:: Figures/disk_rosenfeld.*

   Example of image created with Paraview, using the VTK output of RADMC-3D.
   The model shown here is a warped disk model by Katherine Rosenfeld, in 3-D
   cartesian coordinates with oct-tree AMR refinement.

.. _fig-modeljuhasz-with-vtk:

.. figure:: Figures/model_juhasz_vtk_lowres.*

   Example of image created with Paraview, using the VTK output of RADMC-3D.
   The model shown here is a warped disk model by Attila Juhasz, in 3-D
   spherical coordinates with separable refinement, but without AMR refinement.
   The model is kept low-resolution on purpose, to show the grid structure
   better.