[ REQ 5619]: Stabilising the display

[Stephen.Jones at imag.fr]

I'm using Geomview as a display module within a mobile robot control
architecture. I'm using PVM to communicate with a geomview external
module which translates messages into gcl commands.

I want to show the robot and a free space envelope around
it. Initially I described the robot and the envelope as separate
objects but then I could find no way to set the scale of the two
objects to be the same. So I have them as one object with a sub-object
being the sonar envelope. I send gcl commands to geomview and
redefine this envelope as data arrives from the robot.

As data arrives the size of the sonar envelope changes, geomview
compensates for this and rescales the display to show all of the
envelope. The result is that the robot jumps all over the screen,
ideally, I'd like to keep it centred in the image - how do I do this ?
In other words how do I keep an object centred in the screen whilst
the shapes of others change. One solution might be to fix the camera a
sufficient distance away that it always holds the whole envelope in
view but it would be better if I could just switch off the dynamic
nature of the display.

Hope that you can help, I've exhausted a number of avenues so far
without success,

thanks

Steve