auto-build was enabled, i try to run org.xith3d.test.Xith3DTestLauncher and it works fine.
Then everything is built

.
maybe i don't undestand how eclipse work...i don't saw (and see) the .class file of the two project

i don't know if i'm stupid or blind

, anyway...it works

By default eclipse puts the class files into the same folders than the java files. This is a stupid default behaviour IMHO. But you can change it at project creation time (and by configuring the appropriate defaults). I for example decided to use a "src" forlder for the .java and a "bin" bolder for the .class files, which is quite similar to NetBeans' "src" and "build". And these names are configurable, but this time Eclipse's default is best. I strongly advise you to switch Eclipse's defaults to always use separate "src" and "bin" folders. When you want to archive a piece of code manually, you won't have to strip all the .class files manually.
When the project is built (manually or by auto-build) then class files are put next to the java files or separately into the package structure in the "bin" folder. That's all. Should be nearly the same in NetBeans, isn't it?
Marvin