I was hoping to find some time for this a bit earlier, but better late than never,
(A bit of PDP-1 assembler code…)
Details: This is Snowflake, an early 1960s graphics demo for the PDP-1, with an additional text display. While there is a symbol generator available for the PDP-1, not every PDP-1 came with it (like my emulator), so the text display is implemented as a software renderer. However, this is slow. Therefore the program uses an JIT outline compiler for the characters to gain some speed (this was originally developed for my implementation of Computer Space for the PDP-1) and a faster random number generator (RNG) borrowed from Spacewar. While Snowflake on its own is running even too fast with this RNG, it’s still a bit flickery together with the text. In order to reduce this, the number of dots in any strain of the snowflake has been reduced (6 less per strain), as well.
Alas, there’s still a bit of flicker left. Drawing a dot onto the display is still the major bottleneck for any program on the PDP-1 and this is about as complex as you may get with your graphics.