xranby / pi-eglonx

Raspberry Pi egl on X

Raspberry Pi EGL on X

Demo of Raspbery Pi OpenGL ES rendering to X window posted to raspberrypi.org forums by @teh_orph at http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=6488

Converted to c from c++, added Makefile. Tested on Raspbian.

to run type

cd pi-eglonx
make
./eglonx

Post by @teh_orph

Hello guys,

Quick proof-of-concept: hardware accelerated 3D in an X window. You do not need any fancy X server to make this work. The code provided below only works in a 16-bit 5/6/5 screen though.

Brief summary:
- I took this code: http://wiki.maemo.org/SimpleGL_example
- replaced the eglCreateWindowSurface with eglCreatePixmapSurface
- replaced the swap buffers with a glReadPixels and an XPutImage

Since everything's done in X, all window hiding stuff works fine. You can run multiple EGL programs too. (In the video I run the same program twice - no sharing is being done between them if you're wondering!)

http://www.youtube.com/watch?v=l0i55EndDZQ

CAVEATS:
- eglCreatePixmapSurface seems to be ill-documented for the Broadcom 3D EGL API. Figuring out what to put as the pixmap argument appears to be guesswork!
- X is currently invisible in 24/32-bit mode, and I can't get the pixmap to run in 16-bit mode. So I *in software* glReadPixels the image in 32-bit mode, and then convert to 5/6/5 by hand...this is of course slow. Once it's figured out how to make either a 16-bit pixmap or get 32-bit X working, no conversion will be required.

NB: glReadPixels is powered by the hardware's DMA functionality once the GPU is flushed. The X server it is running on in the video has DMA-enabled blitting, so - assuming the 32->16 conversion is omitted - the whole process would be powered by DMA.