[dekhn]

I used to write opengl screensavers for xscreensaver (glplanet and pulsar) and I have to admit, sometimes when working with opengl it would take me more than a day to just get a triangle (or sphere, my preferred primitive) to show up on the screen. Anything from an errant transform, to a mistaken feature bit (lighting, whatever) turned on/off could make a huge difference. Once I could draw a quad I had everything required for pulsar, and once I could draw a sphere I had everything I needed for glplanet (although I later learned, I did get the projection math wrong the first time).