bugs

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KNOWN BUGS IN SaVi
==================
# $Id: BUGS,v 1.42 2005/02/07 19:21:39 lloydwood Exp $

This list of BUGS describes caveats and problems with use of the SaVi
satellite visualization software. This document contains the following
sections:

1. Caveats in use of SaVi. Be aware of these.

2. A detailed SaVi 1.2 wishlist. Notes on issues in these SaVi releases.
   a. Build issues
   b. Scalability
   c. Scriptability
   d. User interface
   e. Coverage view improvements
   f. Fisheye view improvements
   g. Geomview interaction
   h. Dynamic texturemapping with Geomview
   i. Various
   j. Interaction with other 3D renderers
   k. Interaction with the network simulator ns

3. Remaining integration work from unreleased SaVi 1.1.

4. The original SaVi 1.0 wishlist.



1. CAVEATS IN USE OF SAVI
=========================

Changing default simulation parameters (central body radius,
gravity, etc.) can cause unexpected behaviour; scripts generally
describe satellites in circular orbits via an altitude above the
body's surface. Use at own risk.

Two-line-element (TLE) reading and constellation code in
tcl/constellations.tcl still needs considerable work. Reading
.tle files is experimental. This is not guaranteed for multiple
satellites of different epochs, so you can't yet just download
a .tle file, load it in and go.
Improving this would make SaVi much more practical.

Using sinusoidal coverage map, full coverage reads from 99.6% to 99.8%
due to rounding at curved edges of map.

Mask elevation/satellite cone selection in coverage does not update
fisheye mask circle.

Selection: selected satellite is not visible as selected in Geomview
until a marker type is first selected or satellite orbital elements
are edited. Operations on multiple satellites (e.g. Cut) only work
on the last satellite selected.


2. A DETAILED SAVI 1.2 WISHLIST
===============================

This is an additional wishlist of improvements for SaVi
originally accumulated during work for the SaVi 1.2 release during
October-November 2001, and kept up-to-date with development.

Development takes place at:
http://www.ee.surrey.ac.uk/Personal/L.Wood/software/SaVi/src/unreleased/
http://savi.sourceforge.net/

Many suggestions (such as the user interface and fisheye
modifications) should be straightforward if you have some Tcl/Tk/C
experience and the spare time and interest. Others are difficult.



a. BUILD ISSUES

- Cygwin support isn't seamless, and needs some editing of
  the Tcl Makefile to support the version of Tcl Cygwin uses.
  This caveat only appears to apply to old versions of Cygwin; not
  Cygwin 1.5.6-1 and later.

- $HOST or $HOSTNAME? One or both have the machine info we need
  for the compile version info preserved in Help/About...

- src/Makefile uses $MACH to clean and remove binaries. But Cygwin
  identifies itself as linux, so savi-bin.cygwin is skipped.
  Can we use $ARCH somehow?



b. SCALABILITY

- Scaling up.
  Can SaVi detect available CPU power and e.g. scale number of
  segments in drawn orbit circles/number of sides to a coverage cone
  appropriately for Geomview? A slider or command switch giving some
  control over this would be very useful. Scaling up the number of
  segments when drawing highly-elliptical orbits has been done, but
  ORBIT_SEGMENTS defined in include/constants.h needs to be passed
  to Tcl as a variable.
  More use of Geomview binary format (discussed below) may help.

- Scaling down.
  Geomview rendering is optional; you can conserve CPU by running
  SaVi standalone. SaVi 1.2 doesn't do Geomview calculations when run
  standalone, although 1.0 did.
  Why shouldn't Tk and a graphical display also be optional?
  You do need a Tcl parser - that's essential - but we
  can execute scripts to build satellites and get results; we can
  make use of command-line switches, and we can pipe graphics to
  stdout for a variety of uses, including building web cgis
  (a la Chris Meenan's footprint generator).



c. SCRIPTABILITY

As well as scripts that get results there needs to be a
scriptable interface to record tracefiles. Scriptable recording of
satellite-related values over time periods would be very useful;
the self-scheduling Tcl procedure model that is used in the
network simulator ns (see below) may be worth emulating.



d. USER INTERFACE

Multiple selections: although it's possible to select more than one
satellite in the list by e.g. shift-clicking, only one satellite
at a time is tagged/untagged and shown as selected in coverage
groundtracks and in Geomview, since a single satellite number,
rather than all current cursor selection, is passed through to
the C tag/untag code.

The Tk procedures in tcl/tcl_utils.tcl (inherited from dsTool)
are straightforward to use, but are not that efficient in
using screen real estate. This makes SaVi cluttered, even on a
1024x768 display. SaVi 1.2 has improved things, but this still
needs more work.

* Main panel:
  A realtime push-hold button next to Time Interval would be useful;
  removes Rendering menu (->Geomview menu) when Geomview is not present.
  Move current time into reworked playbar line instead?

* Coverage panel:
  Some wasted space here. When -large-map is selected the playbar
  at end is drawn below the bottom of a 1024x768 screen, which
  is a problem if you can't move windows from available edges.
  Reaching the coverage angle options also becomes tricky.

* Edit satellite:
  Layout can be improved.
  Apply button was removed since values do update live - but does
  that also hold for older versions of Tcl?
  There's no easy way to select multiple satellites so that
  you can change a checkbox setting for all of them.
  Panel can be left open when inappropriate, e.g. when a new
  constellation is loaded in. Should switch to editing a new
  satellite.


Create 'Show all {satellites | orbits | cones | footprints }'
checkboxes that, when checked, force related checkbox (in satellite
Edit parameters) on and the feature visible for all satellites.
When checked off, disable the feature for all satellites. These would
be entries on the Rendering menu, under 'Real-time mode' when
SaVi is run under Geomview.

In 'Edit satellite parameters', the display satellite and display
orbit checkboxes are used only by Geomview, but there is no selectivity
for individual footprints or groundtracks in the 2D coverage window.
Could add more checkboxes.

Update all Earth maps to track more recent political boundaries.

Provide menu of colour choices for highlights etc.



e. COVERAGE VIEW IMPROVEMENTS

When choosing new colour shades after animating forwards then
stopping, the satellites move on an interval unexpectedly as
the map is updated with new colours. Is this due to computed
coverage finally being shown by tk_update()?

Add further shading levels, so that five-level diversity can
be seen and more sense can be made of e.g. GPS coverage.

Improve newly-added spherical projection. Longitude calculation for
fisheye clicks needs doing. Edge calculation methods have visible
differences (as does sinusoidal). Area calculation hasn't been
attempted. We need to source outline Earth maps for this projection.
Look at applying a longitude offset so that Europe/Africa aren't
cut between spheres. Molnya/Tundra demonstrate unusual coverage
at the poles - look at polar plot routine?

Project groundtracks for the next n hours only projects forwards in
time, even if the simulator is currently being run backwards - is
this the least confusing approach?

When altering the coverage map and tiling, remember to run the
Teledesic (840) simulation to check that the top and bottom
of the map are visible as a single line of uncovered (blue or
white) pixels. Tk does require a unit offset.

Add option to fade groundtracks to background over time, just
as interval decay works for coverage areas.

Coverage areas of the selected satellite(s) can be shown in
different shades - possibly shades of green.

Add optional latitude/longitude lines.

Earth outline on sinusoidal map is drawn using different algorithm
to backdrop. Overlap is poor; both should be drawn on the
cached map, rather than on each coverage map drawn. Similarly,
coverage colors should be updated only when changed, rather than
recomputed each time coverage is drawn.

How much work would be required to enable multiple coverage windows
to be spawned, so that multiple projections could be seen, and
any available cylindrical projection used for texturemapping if