I love to play with dust in this sim. But sometimes can be pretty hard to manipulate it.
You can use this to extract pieces of dust. A kinda of revert selection for dust if you will.
This script will read a file called bad.xml and subtract it's contents from a file called all.xml
In the example bellow I created a cube of dust, placed a body inside to "erase" the center, and saved the dust I did not wanted. Then ran the script against the full dusted scenario. The end result was a sphere of dust. :-)
Just remember that the dust must have no speed! Otherwise the dust will move and script won't work.
How to use it:
Get the dust.xml that has all the dust from your scenario. Save it in the same folder where the script files are and rename it all.xml. Now get the parts you want to remove, save in the same folder with the name bad.xml. Finally 2xclick the script (dextract.bat).
The file will create a dust.xml, which is the result of all.xml minus bad.xml.
If doesn't work is because the dust moved from one saved sim (all.xml) to another (bad.xml).