This is the Bubble Universe effect, recently discovered (?)
by yuruyrau on twitter. I thought it looked interesting and worked on
an Apple II version based on some BASIC code of the algorithm found on
pouet.
I started in Applesoft, them moved to 6502 assembly. For speed I have
a super-unrolled screen clear and also a custom HPLOT routine using a lot
of lookup tables. I was using 8.8 fixed point for the math and a lot of
tricks but only could manage around 5fps with I=24,J=24.
I ended up discussing this on the sizecoding discord and it turns out
some other people were working on it too (and we all independently found
the trick that 1/6.28 is roughly $41). However Serato Fig ended up with
the best implementation. From a TIC-80 proof-of-concept to a C64 final
version, a lot of clever optimizations but the most important was that
the effect could be done using only 8-bit integer math, and that a lot
of the scaling/centering could be pushed into the sine tables.
Videos
A hastily grabbed version of the effect, running in the AppleWin emulator:
System Requirements
Should in theory run on any Apple II? Though to be safe
it should probably be one with Applesoft ROMs
How can I run this?
You can download the image below and then try running it on a real machine.
In theory you might also be able to play it in your browser at
the internet archive:
here
Downloads
Disk Image
Here is the disk image for v1.0 (19 February 2024) bubble.dsk (140k)
Got Serato Fig's code going with my Apple II routines. Had some interesting
glitches until I figured out that the sine tables had to be duplicated,
otherwise it would wrap into un-initialized data.
Code is currently not size optimized.
31 December 2023
Initial work on getting things going. Basing it off of BASIC implementation
posted on Pouet. Despite a lot of graphics code optimization,
my version only getting around 5 fps using 8.8 fixed point math.
