A couple examples of simple 3d particle systems using the terrific Libgdx framework.
Taken partly from this tutorial.
To run the Java code, you'll need Gradle version 1.10, which you can find here and look for 'Previous Releases'. To run the scala code, you'll need Scala and SBT which you can find here and here.
Java:
cd java/
gradle desktop:run
Scala:
cd scala/
sbt desktop/run