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How to direct a simple graphics application to a framebuffer of our choice

Started by sudipta Apr 8, 2015 at 9:42 AM 2 replies 3.5k views

Original Post

sudipta

Apr 8, 2015 at 9:42 AM

Hi,

I am a beginner and i was going through the legacy tutorials provided in http://nehe.gamedev.net/ .

I want to direct one of the simple application lets say Lesson 3 of Adding Color i.e.

http://nehe.gamedev.net/tutorial/lessons_01__05/22004/ to a framebuffer of my choice i.e. /dev/fb1.

1. Where in the code i have to modify so as to achieve this?

2. While running the application, how can i verify that it is using /dev/fb1 for display?

Any help in this regard is highly appreciable.

Thanks in Advance,

Sudipta

swiftcoder

Apr 9, 2015 at 2:02 PM

if you are ok with software rendering, it should be fairly straightforward to configure MESA to software-render OpenGL content into /dev/fbX. Please note that this is system configuration, not something you can code in your application.

If you want hardware-acceleration (i.e. to use the actual GPU), then you need one of a variety of experimental drivers which support "OpenGL without X". I don't believe any of these approaches are stable or supported at this time, but you can search around for the 'Wayland' project, or MESA's fbdev/DRI drivers.

A more relevant response, perhaps, is to ask why you want to do this? Apart from a few scenarios involving headless server setups, I'm struggling to come up with a need to render OpenGL directly into the linux framebuffer...

sudipta

Apr 13, 2015 at 6:19 AM

Hi Swiftcoder,

Thanks for your reply. I am trying with graphics overlay on video streaming in which my video will appear on /dev/fb0(background) and the graphics will be overlayed on top of it i.e. /dev/fb1(foreground).But,i am stuck how to direct the graphics(application about which i asked above) to /dev/fb1.

Sudipta

sudipta

Apr 16, 2015 at 7:39 AM

I got it right.

There is a file named fsl_egl.c in which i could set the framebuffer to /dev/fb1 instead of default(as /dev/fb0).

In common/src/fsl_egl.c

#elif (defined EGL_API_FB)

eglNativeDisplayType = fbGetDisplayByIndex(0); //Pass the argument as required to show the framebuffer..

Change it to "1" to have it right on fb1.

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