          TIPSY(1)   Katz and Quinn Release 2.0 (22 MARCH 1994)    TIPSY(1)

          NAME           tipsy - theoretical image processing system

          SYNOPSIS           tipsy [-nodisplay] [-address title] [X options]

          DESCRIPTION           The developement of TIPSY was motivated  by  the
     need  to             quickly  display  and  analyze  the  results of N-body
                simulations.  Most  data  visualization packages  are   designed
                for  the  display  of  gridded  data,  and  hence are unsuitable
                for  use  with  particle data.   Therefore,  a  special  package
               was built that could easily perform the following functions:

               * Display particle  positions  (as  points),  and velocities  (as
               line segments) from an arbitrary viewpoint.

               * Zoom in to a chosen position.  Due to their extremely
     clustered  nature,  structure of interest in an N-body           simulation
     is often so small that it can not be seen when             looking  at  the
     simulation as a whole.

               * Color particles to display scalar fields.  Examples of
     such  fields  are potential energy, or for SPH particles,           density
     and temperature.

               * Selection of a subset of the particles for display and
     analysis.  Regions of interest are generally small subsets           of the
     simulation.

               * Following selected particles from one timestep to another.

               * Finding cumulative  properties  of  a  collection  of
     particles.   This usually involves just a sum over the           particles.

               The basic data structure is  an  array  of  particle  structures.
                Since TIPSY  was built for use with cosmological N-body
     simulations, there are actually three separate arrays for           each of
     the     types    of    particle used    in such    simulations:
     collisionless particles, SPH particles, and star  particles.              A
     single  timestep  is  read  into  these arrays from a disk           file.
     Display is done  by  finding  the x  and  y coordinates  of             the
     particles in  the  rotated coordinate system, and storing           them in
     arrays.  Screen coordinates  are  calculated  from             these arrays
     according  to the current zoom factor.  Also, a           software Z-buffer
     is maintained to save time if  many             particles  project  to  the
     same screen pixel.

               There are several types of  display.   An  ``all plot''
     displays  all  particles  colored  according  to  their  type.   A
     ``radial plot'' will color particles according to the

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          TIPSY(1)   Katz and Quinn Release 2.0 (22 MARCH 1994)    TIPSY(1)

               projection of the velocity  along  the  line-of-sight.   A  ``gas
                plot''  will  color  gas according  to  SPH  quantities  such as
               density, temperature, neutral hydrogen fraction, etc.

               Subsets of  particles  are  maintained  using  ``boxes''.  A  box
                structure  contains  a  bounding box,  and  an array of pointers
               to particles within the box.  All display  and analysis
     functions  are performed  on  the ``active box''.  By default           all
     particles are loaded into box 0, which becomes the           active box.

               If a new timestep is read  from  disk,  all  boxes  are
     destroyed.   A selection  of  particles  can  be  followed between
     timesteps via a ``mark'' array.  Marked particles are             displayed
     in  a  different color, and the analysis functions           can be told to
     only operate on the marked particles.

               To quickly test out tipsy, try the commands:

               openascii run99.ascii

               readascii run99.bin

               loadb 14

               xall

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