Hello Guest

LWJGL running in text mode on Raspberry Pi

  • 3 Replies

Offline Momoko_Fan

  • *
  • 38
  • jME3 lead developer
LWJGL running in text mode on Raspberry Pi
« on: June 22, 2014, 20:40:15 »
Recently I've been trying to see if LWJGL could run on the Raspberry Pi in text mode. There was previous attempts but they require to have an X server running which consumes a lot of RAM, on a system with only 128 MB of memory this is not a good idea... For most games it is not needed to have X server anyway so if it can without it is actually better.

This is a screenshot of LWJGL Gears test running on top of htop (I executed the app via SSH)

And this is the output:
Code: [Select]
[root@malina ~]# java -Dorg.lwjgl.librarypath=$PWD -jar mytest.jar
found mode: 1440 x 900 x 24 @60Hz
found mode: 640 x 480 x 24 @60Hz
found mode: 1024 x 768 x 24 @60Hz
found mode: 1152 x 864 x 24 @60Hz
found mode: 1280 x 544 x 24 @60Hz
found mode: 1280 x 720 x 24 @60Hz
found mode: 800 x 600 x 24 @60Hz
raspi: set mode 1440 x 900 x 24 @60Hz
raspi: create window 1440 x 900 x 24 @60Hz, fs = true
Display Adapter: VideoCore IV HW
Display Version: Jun 18 2014 18:46:58  - 1a6f79b82240693dcdb9347b33ab16f656b5f067 (clean) (release)

GL VENDOR: Broadcom

1029 frames in 4.997 seconds = 205.92354
1101 frames in 4.999 seconds = 220.24405
1133 frames in 5.0 seconds = 226.6
1135 frames in 4.999 seconds = 227.04541

Unfortunately to make the native library I couldn't really use the existing Linux natives as they required X11 ..  Instead I created a new platform under platform_build for the raspberry pi which does not include X11 and instead depends on the broadcom libraries like libbcm_host.so. You do not need to have a raspberry pi or ARM machine to build the native because it uses the raspberry pi cross compiler available on github.

If there's any interest I can put up the code on github, at the moment though it is missing support for input, cursors, and some other stuff (audio via OpenAL works though).
« Last Edit: June 22, 2014, 20:44:01 by Momoko_Fan »


Offline Momoko_Fan

  • *
  • 38
  • jME3 lead developer
Re: LWJGL running in text mode on Raspberry Pi
« Reply #1 on: June 24, 2014, 21:05:49 »
I looked into implementing input on Raspberry Pi without X11, it turns out there's /dev/input/event*** which expose input devices and are accessible by users in the "input" group on the Raspberry Pi. However, it's a quite low level interface and missing many functions need to support all features in LWJGL. Specifically: absolute mouse coordinates, hardware cursor and scan code to character translation. I found that libSDL2 already implements all of these functions on the Raspberry Pi so what I am planning to do is just copy their code over and implement it according to LWJGL's interfaces.

Once that's covered, the only thing left is joystick support which is already provided on Linux via JInput, it also uses /dev/input/event*** hence no reliance on X11 and should work out-of-the-box on the Raspberry Pi.


Offline spasi

  • *****
  • 2258
    • WebHotelier
Re: LWJGL running in text mode on Raspberry Pi
« Reply #2 on: June 25, 2014, 11:13:16 »
Interesting stuff.

Would you be interested to work on this using the LWJGL 3 codebase? It should be much simpler to create the bindings you need and not have to support pre-existing behavior. Note that the plan is (not implemented yet) to be able to build LWJGL 3 with alternative backends and conditionally include only the bindings required by your application, which should be ideal for Raspberry apps.


Offline Momoko_Fan

  • *
  • 38
  • jME3 lead developer
Re: LWJGL running in text mode on Raspberry Pi
« Reply #3 on: June 25, 2014, 21:00:26 »
Oh that's pretty cool! So far it definitely seems like a step in the right direction, but based on the code it looks alpha stage to me.

In any case, I think I'll apply the LWJGL 3 principles to create the LWJGL 2 Raspberry Pi backend, e.g. have a separate class with all public native methods that interact with the RPI APIs, to ease the porting effort (if any). At least until LWJGL 3 matures, that would have to do.