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I'm trying to make an embedded system which will allow people to rotate and generally view a 3D model on a touchscreen. I am using Raspberry Pi 3 for that. The OpenGL part is not a problem as I already have experience with WebGL, but I'm having a lot of trouble making some way for the app to be able to display anything on Raspberry.

I installed minimal Raspbian and after a bit of research realised that KMS with direct buffering is the best choice, but... it seems this raspbian doesn't even have DRI (or at least, /dev/dri).

How can I make such an app for Raspberry Pi? What options do Pi's hardware and drivers provide?

  • I would have thought your best bet would be to run X with a minimal desktop manger then just run any standard openGL code. Rather than trying to run directly in framebuffer. – rob Apr 20 '18 at 10:05
  • @rob "any standard openGL code" still needs a surface and a context, which need to be initiated in some way. Also, a minimal desktop manager isn't needed as if you already have an X client you want to display, you can just startx it directly. – Deuxis Apr 20 '18 at 20:29
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I ran out of time and ended up using a kiosk-mode Chromium with a canvas as a WebGL context supplier, but here's what I gathered:

  1. Raspberry Pi 3 has the option to enable DRM. It's in options presented by running raspi-config, under Advanced Options -> Enable experimental GL Driver or something like that.
  2. If you have a program providing a context for you that is also an X client (which currently means any graphical Linux program), such as Chromium in my case, the most efficient way to run it is to use nodm to log into a special user, whose .xinitrc does exec yourprogram, and use that .xinitrc to initiate an X session.
  3. Chromium has a whole lot of command line switches that enable you to set kiosk mode, without any navigation features, and window geometry/offset, and it's actually pretty light. If you are in the same situation as me, it's actually a pretty good choice.

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