C64 SineHat - Modern Version

READY.

SYS 1983

In 1983, I was reading a computer magazine, likely Compute!, that featured an advertisement for a PET computer graphics card. The ad showed a 3D plot of a hat, and I was inspired to try and recreate it on my C64. After consulting the C64 Programmer's Reference Manual to learn how to plot on the high-resolution screen, I wrote the code in C64 BASIC V2. It took 23 minutes to run!

Later, I found that using a SuperExpander cartridge improved the plot time to 13 minutes. As time passed, I optimized that SuperExpander code further, bringing the runtime down to 3 minutes. This webpage visualizes the "Sine Hat," allows you to adjust parameters, and displays the original BASIC, SuperExpander, and optimized code.

Over the decades, I enjoyed porting the code to various languages and devices. It became my "Hello World" program. Finally, in 2026, Gemini Pro 3.1 AI produced a C64 Assembly version that ran in just 9 seconds. That's a massive improvement over my original 23-minute journey.

READY.

LIST

0 REM C64 BASIC SINEHAT 1983
3 REM PLOT TIME 23 MINS
5 BASE=2*4096:POKE53272,PEEK(53272)OR8
10 POKE53265,PEEK(53265)OR32
20 FOR I=BASETOBASE+7999:POKE I,0:NEXT
30 FOR I=1024TO2023:POKE I,80:NEXT
100 DR=3.1415/180:VA=15:S=0.3:RS=5:TS=5
130 FOR R=30 TO 330 STEP RS
140 FOR T=0 TO (360-TS) STEP TS
150 X=R*COS(T*DR)*S
160 Y=R*SIN(R*DR)*S
170 Z=R*SIN(T*DR)*S
180 XP=160+X+(COS(VA*DR)*Z)
185 YP=60-(Y+(SIN(VA*DR)*Z))
200 CH=INT(XP/8):RO=INT(YP/8):LN=YPAND7
230 BY=BASE+RO*320+8*CH+LN:BI=7-(XPAND7)
250 POKEBY,PEEK(BY)OR(2^BI)
300 NEXT T:NEXT R
520 GETA$:IFA$=""THEN520
525 POKE 53265,PEEK(53265)AND223
530 POKE 53272,PEEK(53272)AND247

STANDARD SUPEREXPANDER * 13 MINS RUNTIME *

READY.

LIST

COMMODORE 64 SINEHAT 1983