code: public void setVelocityRange( final Vector3f minV, final Vector3f maxV )
      {
          if (null != mGVRContext) {
              mGVRContext.runOnGlThread(new Runnable() {
  
                  @Override
                  public void run() {
                      minVelocity = minV;
                      maxVelocity = maxV;
                  }
              });
          }
      }
docs: The range of velocities that a particle generated from this emitter can have.
  @param minV Minimum velocity that a particle can have
  @param maxV Maximum velocity that a particle can have