My question was wrong because of my lacking of knowledge about using camera in the game so I deleted this post !
Sorry For Bothering
Sorry for bothering with my stupid question !!
Actually the answer was in front of my eyes but I was not able to see it
I solved it by
flyCam.setEnabled(true);
flyCam.setDragToRotate(false);
flyCam.setMoveSpeed(100);
this.cam.setFrustumFar(2000);
this.cam.setFrustumNear(10);```
thanks from @nakou
You can also open up the source code to anything in JME to see how it works… like the FlyByCamera… FlyCamAppState, SimpleApplication, etc…
Because this:
.setFrustum(speed, speed, speed, rotate, speed, rotate);
…makes no sense at all, FYI
Thanks Paul
Yes it was my bad …
As you mentioned right now I am studying FlyByCamera source code .