Here is an easy way to do a virgin install of picrate and jruby on a RaspberryPI with (Raspbian Stretch OS).

Download my Rakefile and run as follows:-

rake # to run default task of Rakefile

To list rake Tasks:-

rake --tasks

NB: you will be prompted for password as some tasks require sudo authority (but you should not run rake with sudo authority)

Once everything is installed you can use geanyIDE to explore example sketches (after loading PiCrate project) or to run demo from console:-

cd `~/picrate_samples`

For opengl sketches (P2D, P3D) use vc4 graphics driver

dmesg | grep drm
[    4.856264] vc4-drm soc:gpu: bound 3f600000.firmwarekms (ops vc4_fkms_ops [vc4])
[    4.897489] vc4-drm soc:gpu: bound 3fc00000.v3d (ops vc4_v3d_ops [vc4])
[    4.902987] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on minor 0
[    4.903007] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[    4.903015] [drm] Driver supports precise vblank timestamp query.
[    5.024078] vc4-drm soc:gpu: fb0:  frame buffer device

For video capture use the legacy driver.