***  The most recent versions are at thebottom of this thread ***
 
I'm going to start making the beta versions public, as the beta is now far superior to the 2.0 version, and the new featuress seem to be quite stable.
 
This is the latest version.  It runs about 60% faster than the previous beta version, at least on my computer.  I'd be curious to know what results others get.
http://orbitsimulator.com/gravity/beta/GravitySimulatorBeta17Apr2007.exe
 
Download it into the same folder as your existing gravitysimulator.exe or your existing beta version and use it instead.
 
Future versions of the beta will include a contribution from frankuitaalst:  an Picard integrator.  So stay tuned...

This one may be quicker yet, depending on how many objects are in your simulation.  Give it a try and let me know what you think.  Create a new folder for this one, and copy all 3 files into the folder:
http://orbitsimulator.com/gravity/beta/GravitySimulatorBeta22Apr2007.exe
http://orbitsimulator.com//gravity/beta/CodeOptomizer.dll
http://orbitsimulator.com//gravity/beta/resume.gsim
 
You can use any resume.gsim that you want.  It's just important that there is one in your folder.  This CodeOptomizer.dll is different than the one you have now.  It's the same code, just compiled more efficiently.  This is why I suggest you create a new folder.
 
And remember, this is a beta version, .so there may be bugs to be ironed out. And the new .dll may not work with all processors.  If you have trouble or successes, I'd love to know.
 
Richard "Publius", "Grav", and others from the Bad Astronomy forum are helping me with this one.  
http://www.bautforum.com/showthread.php?t=57336

Download these into the same folder:
http://orbitsimulator.com/gravity/beta/GravitySimulatorBeta4Dec2007.exe
http://orbitsimulator.com//gravity/beta/CodeOptomizer.dll  
http://orbitsimulator.com//gravity/beta/resume.gsim
 
There are no huge changes.  But there's a new feature that lets you add a description to your simulations in the file menu.

Quote from Tony on 01/20/08 at 02:17:34:

Good job , I tried the new version.  
Seems to work fine , adding new bodies with the 1SD works ...
But running the program I got this flickering picture ... any idea why ?  

Quote from Tony on 01/20/08 at 02:17:34:

 
Are you using different compiling software? I think that can change the exe size, if it's compiled more efficiently.

Tony,  I just tried the latest beta, I have not noticed anything wrong. So it looks good. However I did have one question, are you still planning to implement the ability to edit object using the same variables used to create them. I am working on a system with 12 planets, trying to figure out a stable resonance, and I find it somewhat frustrating having to reenter all the variable because the current edit object just give the XYZ and motion vector.  
 
Thanks
 
-Matt-

http://orbitsimulator.com/gravity/beta/GravitySimulatorBeta2008November4.exe
 
There is a feature I introduced a few versions ago, but it was buggy, so I fixed and improved it.  It's the "Pointer" feature.  To use it, choose menu View > Show Pointer
It allows you to place an arrow on the screen that points to an object of your choosing.  When you first display the pointer, it points to the Sun.  You can drag it around the screen by dragging the words "To Sun".  To change the object it points to, right click the words "To Sun" and a dropdown list will appear that allows you to change the object.
 
Another change I made is that you can fine-tune the rotation of the rotating frame.  As it was, if you were in rotating frame, Pressing "<" or ">" (you had to hold the shift key) rotated the rotating frame by 36 degrees, so 10 presses made a complete circle.  Now "<" and ">" shift it by 0.5 degrees, and "." and "," (which are < and > without the shift key) rotate the rotating frame by 36 degrees.
 
 
What inspired these fixes is that I wanted to recreate the diagram and trajectory on this page:
http://neo.jpl.nasa.gov/news/2008tc3.html
(I'm hotlinking their image  )
 
And here's my effort

 
 
To try this yourself, download this simulation
http://orbitsimulator.com/gravity/simulations/2008TC3earthcenteredview.gsim
 
This simulation is in a rotating frame with a very long period (quadrillions of years).  This allows you to have basically a non-rotating frame, while giving you the ability to adjust the orientation.
 

• Run the simulation, and use the "<>,." buttons to rotate the screen until the Sun pointer points straight down.  Don't worry if you're not fast enough to do it before the asteroid impacts Earth.
  
• Pause the simulation
  
• Re-open the simulation (it should now be the first simulation in the "recently opened" simulations in the File menu.
  
• Increase the time step to .06
  
• Unpause the simulation
  
• Autopilot will pause the simulation for you a few moments before impact, so the screen won't clear on you
  
• You should now have the same image as above.
  

 
With the time step set to .06 seconds, and the graphics update in the Preferences menu set to 15000, you get 1 tick every 15000*.06=900 seconds, or every 15 minutes like the Nasa image.
 

http://orbitsimulator.com/gravity/beta/GravitySimulatorBeta2009February25.exe
 
menu Time > Time Step Control
 
Enable the control by clicking "on".
Set the minimum distance two objects are allowed to pass before the time step slows.
Set the slow time step.
Set the fast time step.
If you want a log of the time step changes, select the "report" option.
 
For example, if you started with a simulation of all the planets plus Earth's moon, you would want to set your minimum distance to less than about 90% of the moon's distance.  Let's choose 300,000 km.  Since the moon is always farther than this, this prevents it from triggering a slow time step.
 
Enter 2048 for the fast time step.
Enter 1 for the slow time step.
Choose to make a report.
 
Your simulation should run at time step 2048 unless any two objects are within 300,000 of each other, in which case it will run at time step 1 until the close encounter is over.
 
It doesn't check for close encounters with each iteration.  Rather it is controlled by the "Do Events" interval in the preferences menu.  This is set to 50 by default, but you may want to slow it down to 5.