Draft of complete paper.

doc/iau208/partiview.tex

 % $Log$
+% Revision 1.6  2002/07/03 13:27:17  slevy
+% Draft of complete paper.
+%
 % Revision 1.5  2002/06/29 07:03:07  slevy
 % ...
 %
@@ -62,17 +65,17 @@ flexible display of particles in 3-space.
 
 Input data to partiview is provided as a (possibly time-varying)
 collection of particles, each with a 3-D position and an arbitrary number
-of other floating-point attributes ("fields"), and a configuration script
+of other floating-point attributes ({\it fields}), and a configuration script
 specifying which fields to map into visible properties,
-including color and luminosity.  For example, if a field were named Tlog,
+including color and luminosity.  Text-based commands can change
+these selections interactively, switching between coloring stars by
+e.g. temperature, mass, or space velocity on the fly.
+For example, if a field were named Tlog,
 {\verb"  color Tlog 3.2 4.5
 "}
 assigns colors by using the Tlog field as an index into a
 user-supplied color table via a linear mapping
 that associates 3.2 and 4.5 with the colormap's endpoints.
-Text-based commands can change these selections interactively,
-switching between coloring stars by e.g. temperature, mass, or
-space velocity on the fly.
 
 From each particle's luminosity and distance from the current
 viewpoint, partiview draws a dot whose screen brightness and size
@@ -84,10 +87,10 @@ is good enough to yield plausible naked-eye starfields given a table
 of stellar luminosities, colors and 3-D positions as in Figure~1,
 drawn using Hipparcos data.
 
-This sort of viewpoint-dependent apparent brightness
+This kind of viewpoint-dependent apparent brightness
 is a feature that few other scientific visualization
 packages seem to offer, even though it's
-inexpensive to compute and can be useful.
+inexpensive to compute and can be useful.  
 (Where not useful, as when making orthographic
 plots of 3-D scenes, it can be switched off in partiview.)
 
@@ -100,34 +103,38 @@ over all particles or the selected subset.
 
 \begin{figure}
   \psfig{figure=starfield.ps,height=2.0in}
-  \caption{Figure~1. Desktop version of partiview showing star field
-    from Hipparcos data with Sun at upper left, marked by 0.1 pc crosshair.}
+  \caption{Desktop version of partiview showing star field
+    from Hipparcos data with Sun at upper left, marked by 0.1 pc crosshair.
+    Normally displayed in light colors on a dark background, this and all
+    images in this article are rendered as black-on-white for publication.}
 \end{figure}
 
 \begin{figure}
   \psfig{figure=ncsa-haydenCollab2.ps,height=2.0in}
-  \caption{Figure~2.  Virtual Director version: collaborating between
-    Hayden Planetarium (dome avatar at lower left) and NCSA while designing an animation path
-    in a simplified Milky Way model.}
+  \caption{Virtual Director version: collaborating between
+    Hayden Planetarium (dome avatar at lower left) and NCSA while
+    designing an animation path in a simplified Milky Way model.}
 \end{figure}
 
-% \begin{minipage}{2.7in}
-% 	\centerline{\hbox{
-% 	\psfig{figure=starfield.ps,height=2.3in}
-% 	}}
-% 	\centerline{Figure~1. Desktop version of partiview showing star field
-% from Hipparcos data with Sun at upper left, marked by 0.1 pc crosshair.}
-% \end{minipage}\    \
-% \begin{minipage}{2.7in}
-% 	\centerline{\hbox{
-% 	\psfig{figure=ncsa-haydenCollab2.ps,height=2.3in}
-% 	}}
-% 	\centerline{Figure~2.  Virtual Director version: collaborating between
-% Hayden Planetarium (dome avatar at lower left) and NCSA while designing an animation path
-% in a simplified Milky Way model.}
-% \end{minipage}
+\section{Scripting}
+
+Partiview can be controlled by external scripts in a limited way,
+by invoking a subprocess which emits a series of partiview commands.
+This allows writing, for example, animation-recording programs which
+drive partiview to display some computed sequence of views and record
+each image to a file.  It may be adequate for creating simple
+graphical controls for features of partiview that aren't
+provided on the existing graphical panel.  The major limitation
+is the lack of feedback: there's no way for external driver programs
+to read out the viewer's state.
+
+A future version of the software may have an embedded scripting language,
+perhaps Python or Ruby.  This should make it easier to offer a variety
+of graphical interfaces (or to change the graphical interface dynamically),
+to couple the viewer more easily with external data-mining tools, and so on.
 
 \section{Desktop and dome}
+
 The same graphical and data-handling code is embedded
 in multiple guises for different computing environments.
 Both accept the same data and configuration files, and most of the same
@@ -137,11 +144,12 @@ with conventional buttons and sliders for common controls,
 available for Unix-like systems and for Windows.
 Figure~2 shows the virtual-reality version,
 built using the Virtual Director virtual-choreography framework
-and the CAVE library; it is currently restricted to Silicon Graphics computers
+and the CAVE library $<$http://www.evl.uic.edu/pape/CAVE/$>$;
+it is currently restricted to Silicon Graphics computers
 but can run on systems with multiple graphics pipes.
 
 Though the latter was originally written for the
-CAVE virtual reality room at NCSA, it is used elsewhere too.
+CAVE virtual reality room at NCSA, it is used elsewhere as well.
 The Hayden Planetarium at the American Museum of Natural History
 in New York built a Silicon Graphics-driven display for their
 planetarium dome; this turned out sufficiently
@@ -159,7 +167,7 @@ some animations for Hayden's 2002 space show, as seen in Figure~2.
 
 \section{N-body dynamics: examining Starlab traces}
 
-Stellar dynamics simulations done in Starlab [ref?]
+Stellar dynamics simulations done in Starlab $<$http://www.manybody.org/$<$
 produce "traces", recording various information about each star
 as a function of time: physical properties such as mass,
 luminosity and temperature; position and three time derivatives;
@@ -168,15 +176,16 @@ and hierarchical descriptions (binary trees) of interacting groups.
 Partiview, coupled with the Starlab libraries to read and interpolate
 traces, is adapted to display these properties as the cluster evolves.
 
-Figure~3 shows a cluster evolving in a tidal field
-[[with stars colored by mass]].  "Trails" show the recent motion
+Figure~3 shows a cluster evolving in a tidal field.
+"Trails" show the recent motion
 history of each star, so long trails show high speed, and curved ones
-high acceleration.  Note the stars escaping through the tidal [[tails?]] at left and right.
+high acceleration.  Note the stars escaping through the tidal tails
+\edcomment{Tails?} at left and right.
 
 \begin{figure}
   \psfig{figure=0607.ps,height=2.5in}
-  \caption{Figure~3.  Star cluster dispersing in a tidal field,
-    with recent motion shown by trails.  Small circles indicate binary or
+  \caption{Star cluster dispersing in a tidal field,
+    with recent motion shown by trails.  Small circles denote binary or
     multiple systems.}
 \end{figure}
 
@@ -198,43 +207,94 @@ serve a dual purpose: their positions show the center-of-mass location,
 and their lengths are proportional to the instantaneous true separation
 of the nodes on that branch.
 
-Note the triple system [[in magenta]]: although in this view the
+Note the triple system.  Although in this view its
 lower-right pair of stars seem very close together, this must be a 
 projection effect; as shown by the tick marks, their true separation
 is nearly as large as that from their center-of-mass to the upper-left star.
 
-[[ Each star's dynamical state is sufficiently finely sampled in time
-to allow accurate interpolation, generally at some fixed multiple of the
-internal simulation timestep.   Thus stars in dense regions
-may have far more frequent trace entries than isolated stars.
-The Starlab libraries offer functions to interpolate the state of the
-simulation at any time. ]]
+% Each star's dynamical state is sufficiently finely sampled in time
+% to allow accurate interpolation, generally at some fixed multiple of the
+% internal simulation timestep.   Thus stars in dense regions
+% may have far more frequent trace entries than isolated stars.
+% The Starlab libraries offer functions to interpolate the state of the
+% simulation at any time.
+
+Stellar cluster simulations, with time scales spanning many orders
+of magnitude, need some sort of temporal microscope too.  Partiview has
+limited facilities for this, with a logarithmic speed scale
+(simulation time per unit displayed time), keystroke commands to
+home in on interesting events, and a trip meter to mark a (single)
+time reference point.  
+
+
+\section{Sifting needles from a haystack}
+In all but the smallest systems, direct visual inspection quickly becomes
+an impractical way to study interaction patterns -- too many stars
+clutter the view.  But visualization might still be helpful, if there is a way
+to focus on a subset of the system that sheds light on the question at hand.
+
+For example, to study some sequence of events -- the ejection of a star
+from the cluster, or the formation of a hard binary -- one might
+imagine focusing by looking at some limited neighborhood,
+e.g. all stars passing through some volume during some time interval.
+But, since starlab simulation traces explicitly mark
+closely-interacting stars, we can do better than that; we can 
+use {\it interaction tracking} to pick out just the set of stars that
+pass close enough to be dynamically important.
+
+To do this, the user constructs an initial small
+{\it selection-set} $S$ of interesting stars at a given time -- perhaps by
+a threshold of some field ("all stars with mass exceeding 30 $M_sun$", or
+"all triple systems", or "star number 1792"), or by clicking on some star,
+e.g. an escapee.  This set is given to a {\verb"kira intsel $T$ = $S$"}
+command, and the user plays the trace forward or backward in time
+for a while.  When {\verb"intsel"} is in effect, whenever any member of
+$S$ interacts with another star, the software adds the latter star to the set $T$.
+If $S$ and $T$ refer to the same set, then that set accumulates the transitive
+closure of interactions with $S$.
+
+Other commands can then use membership in $T$ to
+affect the display: to show only stars which have
+or haven't interacted during the given time span; to show all stars,
+but brightening those in $T$; to draw trails behind those selected; etc.
+
+\section{Other views}
+Of course, plots of 3-D positions aren't the only
+useful way to display the state of a cluster.  For Starlab traces which
+record stellar temperature and luminosity, a Hertzprung-Russell
+diagram is also available, as shown in Figure~5.  One can click on a star
+in either view and locate it in the other.
 
-[[ Temporal microscope too. ]]
+\begin{figure}
+\psfig{figure=hyades-hrdiag.ps,height=2.2in}
+\caption{H-R diagram}
+\end{figure}
 
-[[ Interaction tracking.  One more figure? ]]
+Other types of views are contemplated for future work;
+for example, worldline plots of two spatial dimensions plus time,
+or a velocity-space plot.
 
 \section{Offerings}
-The desktop version of partiview is available as open source from
+The desktop version of partiview is available as open source software from
 the Starlab CVS archive; see Peter Teuben's web pages at:\hfill\break
-{\verb"    http://www.astro.umd.edu/nemo/amnh/"}
+$<$http://www.astro.umd.edu/nemo/amnh/$>$.
 
-Also, Brian Abbott and Carter Emmart of the American Museum of Natural
+Brian Abbott and Carter Emmart of the American Museum of Natural
 History have assembled a 3-D Milky Way model (nearby stars,
-open and globular clusters, H II regions, pulsars, etc.) from various
+open and globular clusters, H~II regions, pulsars, etc.) from various
 sources and are offering it in partiview form, along with partiview itself
 for Linux and Windows, on the Hayden Planetarium web site:\hfill\break
-{\verb"     http://www.haydenplanetarium.org/hp/vo/partiview/index.html"}
+$<$http://www.haydenplanetarium.org/hp/vo/partiview/index.html$>$.
 
 \section{Acknowledgements}
 Thanks are due in many directions: to my colleagues Donna Cox and
 Robert Patterson at NCSA who've encouraged me to develop this;
 to them and other patient users, Emmart and Abbott of Hayden/AMNH; Brent Tully
-of U. of Hawaii; Piet Hut, Steve McMillan, Simon
-Portegies-Zwart and others of the Starlab group.  All have offered data
+of U. of Hawaii; Piet Hut, Peter Teuben, Steve McMillan, Simon
+Portegies-Zwart, and Jun Makino of the Starlab group.  All have offered data
 to visualize and plenty of good ideas, a few of which are implemented here.
-Special thanks are due to Peter Teuben, who wrote much of the extant
-documentation, and Steve McMillan for the Starlab interface libraries.
+Special thanks are due to Teuben, who wrote much of the extant
+documentation, and to McMillan for the Starlab interface libraries.
 Thanks finally to the NCSA, which is supported in turn
 by the National Science Foundation and by the state of Illinois.
 \end{document}