The code is here PART1 * = $1000 LDA #0 ; black everywhere :) STA $D021 ; =53281 STA $D020 ; =53280 START ; first step is to create a table with sine + cosine values ; The addition is performed on a proportionate basis ; the table is changed on every frame LDX #64 ; 25 rows (+40 additional values) loop LDA sin,X addpart ADC cos,X ; Y can be used as index ; insofar as it's decremented STA sinecosine,x ; new table DEX BPL loop ; values in sine + cos table are changed INC loop+1 ; after each frame DEC addpart+1 ; the first 40 succesive values represent a value ; for each of the 40 columns ; The 25 following successive values represent the 25 rows ; Once the sine + cos table with the 65 values is created ; The code adds and combines them giving 1,000 different values ; values 0-39 in the table : column ; values 40-64 in the table : row ; the routine deals each column, line by line LDX #39 PLOT LDA sinecosine,x ;LSR STA $10 ; address $10 in memory will be used ; to store the value used ; for each column ; row/line 0 ADC sinecosine+40 ; value for row/line 0 TAY LDA charcode,y ; load the charcode from a table STA $0400,x ; read and indexed with Y ; and store it in the screen memory LDA colorcode,y ; same thing about color memory STA $d800,x ; operation is repeated every ; 25 screen rows/lines ; row/line 1 LDA $10 ADC sinecosine+41 TAY LDA charcode,y ; load the charcode from a table ; read and indexed with Y STA $0400+40,x ; and store it in the screen memory LDA colorcode,y ; same thing about color memory STA $d800+40,x ; row/line 2 LDA $10 ADC sinecosine+42 TAY LDA charcode,y STA $0400+80,x LDA colorcode,y STA $d800+80,x ; row/line 3 LDA $10 ADC sinecosine+43 TAY LDA charcode,y STA $0400+120,x LDA colorcode,y STA $d800+120,x ; row/line 4 LDA $10 ADC sinecosine+44 TAY LDA charcode,y STA $0400+160,x LDA colorcode,y STA $d800+160,x ; row/line 5 LDA $10 ADC sinecosine+45 TAY LDA charcode,y STA $0400+200,x LDA colorcode,y STA $d800+200,x ; row/line 6 LDA $10 ADC sinecosine+46 TAY LDA charcode,y STA $0400+240,x LDA colorcode,y STA $d800+240,x ; row/line 7 LDA $10 ADC sinecosine+47 TAY LDA charcode,y STA $0400+280,x LDA colorcode,y STA $d800+280,x ; row/line 8 LDA $10 ADC sinecosine+48 TAY LDA charcode,y STA $0400+320,x LDA colorcode,y STA $d800+320,x ;row/line 9 LDA $10 ADC sinecosine+49 TAY LDA charcode,y STA $0400+360,x LDA colorcode,y STA $d800+360,x ;row/line 10 LDA $10 ADC sinecosine+50 TAY LDA charcode,y STA $0400+400,x LDA colorcode,y STA $d800+400,x ;row/line 11 LDA $10 ADC sinecosine+51 TAY LDA charcode,y STA $0400+440,x LDA colorcode,y STA $d800+440,x ;row/line 12 LDA $10 ADC sinecosine+52 TAY LDA charcode,y STA $0400+480,x LDA colorcode,y STA $d800+480,x ;row/line 13 LDA $10 ADC sinecosine+53 TAY LDA charcode,y STA $0400+520,x LDA colorcode,y STA $d800+520,x ;row/line 14 LDA $10 ADC sinecosine+54 TAY LDA charcode,y STA $0400+560,x LDA colorcode,y STA $d800+560,x ;row/line 15 LDA $10 ADC sinecosine+55 TAY LDA charcode,y STA $0400+600,x LDA colorcode,y STA $d800+600,x ;row/line 16 LDA $10 ADC sinecosine+56 TAY LDA charcode,y STA $0400+640,x LDA colorcode,y STA $d800+640,x ;row/line 17 LDA $10 ADC sinecosine+57 TAY LDA charcode,y STA $0400+680,x LDA colorcode,y STA $d800+680,x ;row/line 18 LDA $10 ADC sinecosine+58 TAY LDA charcode,y STA $0400+720,x LDA colorcode,y STA $d800+720,x ;row/line 19 LDA $10 ADC sinecosine+59 TAY LDA charcode,y STA $0400+760,x LDA colorcode,y STA $d800+760,x ;row/line 20 LDA $10 ADC sinecosine+60 TAY LDA charcode,y STA $0400+800,x LDA colorcode,y STA $d800+800,x ;row/line 21 LDA $10 ADC sinecosine+61 TAY LDA charcode,y STA $0400+840,x LDA colorcode,y STA $d800+840,x ;row/line 22 LDA $10 ADC sinecosine+62 TAY LDA charcode,y STA $0400+880,x LDA colorcode,y STA $d800+880,x ;row/line 23 LDA $10 ADC sinecosine+63 TAY LDA charcode,y STA $0400+920,x LDA colorcode,y STA $d800+920,x ;row/line 24 LDA $10 ADC sinecosine+64 TAY LDA charcode,y STA $0400+960,x LDA colorcode,y STA $d800+960,x DEX BMI loop_exit JMP PLOT loop_exit LDY #50 @exit DEX BNE @exit @exit2 DEY BNE @exit JMP START ALIGN ; here the code is aligned ; so that the LB adress is at $00 charcode DCB 16,195 ; DCB 16,196 ; number of bytes used will determine DCB 16,197 ; the thickness of the layers pattern DCB 16,198 ; DCB 16,195 DCB 16,196 DCB 16,197 DCB 16,198 DCB 16,195 DCB 16,196 DCB 16,197 DCB 16,198 DCB 16,195 DCB 16,196 DCB 16,197 DCB 16,198 ALIGN ; here the code is aligned ; so that the LB adress is at $00 colorcode DCB 16,00 DCB 16,11 DCB 16,12 DCB 16,15 DCB 16,00 DCB 16,11 DCB 16,12 DCB 16,15 DCB 16,00 DCB 16,11 DCB 16,12 DCB 16,15 DCB 16,00 DCB 16,11 DCB 16,12 DCB 16,15

Merci pour l'explication détaillée, la démarche pour obtenir l'effet est très claire :)

thanks for the info. It all makes sense now when i see 1k demo

Thanks for making the video and going thru it in detail.

Great video. Thank you very much!

Nice example how to properly self modify code. :) After cofing on C64 I thought that self modifying code is normal thing. When I started with PC, I was surprised that people don't use such tricks. Anyway, I would like to see how people do video playback on C64.

Thank you for this video, it was a pleasure for me to change the datas (charcode & colorcode) for fun. Here's my example: charcode DCB 8, $ef DCB 8, $d2 DCB 8, $c6 DCB 8, $c0 DCB 8, $C3 DCB 8, $C4 DCB 8, $C5 DCB 8, $f7 DCB 8, $ef DCB 8, $d2 DCB 8, $c6 DCB 8, $c0 DCB 8, $C3 DCB 8, $C4 DCB 8, $C5 DCB 8, $f7 DCB 8, $ef DCB 8, $d2 DCB 8, $c6 DCB 8, $c0 DCB 8, $C3 DCB 8, $C4 DCB 8, $C5 DCB 8, $f7 DCB 8, $ef DCB 8, $d2 DCB 8, $c6 DCB 8, $c0 DCB 8, $C3 DCB 8, $C4 DCB 8, $C5 DCB 8, $f7 colorcode DCB 8,$09 DCB 8,$08 DCB 8,$07 DCB 8,$01 DCB 8,$01 DCB 8,$07 DCB 8,$08 DCB 8,$09 DCB 8,$09 DCB 8,$08 DCB 8,$07 DCB 8,$01 DCB 8,$01 DCB 8,$07 DCB 8,$08 DCB 8,$09 DCB 8,$09 DCB 8,$08 DCB 8,$07 DCB 8,$01 DCB 8,$01 DCB 8,$07 DCB 8,$08 DCB 8,$09 DCB 8,$09 DCB 8,$08 DCB 8,$07 DCB 8,$01 DCB 8,$01 DCB 8,$07 DCB 8,$08 DCB 8,$09 And you ? Share your proposal here...