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2024-07-27 05:50

Repose

Registered: Oct 2010
Posts: 227

fastest plotter

Does anyone know the record for most pixels plotted per frame?
The best I can imagine is between 500 and 800 hires pixels (NTSC).
I think the quickest way is to use redefined charsets to create an ideal memory layout.
Imagine a vertical layout with (theoretically) 32 chars down. With 8 bytes per character that equals 256 bytes. That means y is itself as the offset. Each x/8 becomes the high byte, or (x&$fb)<<3. So the plot is just:

lda tabl,x ;4
sta zp+1 ;3
lda (zp),y ;5 never crosses page boundary
eor plot,x ;4
sta (zp),y ;5
;21, about 811 pixels per frame
alternate, plot only
lda plot,x ;4
sta (zp),y ;5
;16

One charset is only 8 chars by 32 chars so a pixel plot area of 64x200, but you can make a fast extension by changing the charset pointer at $d018 each raster, for 128 lines, taking 14 cycles (lda #base0:sta $d018:lda #base1:nop:sta $d018) plus sync code each line.
Now we have two charsets, 8x32 and 8x32, for a cropped 128x128 plot area.

For comparison, a hires plot is about 32 cycles.

The erasing has to be added too. Depending on what you're plotting, you might be able to overwrite it, but a full erase is 16x128=2048 bytes.
Or, eor the same pixels again for exactly half the speed.

I suppose a 16x16 layout is just as fast? The formula has two x components, but I think they could be combined.
byt=y+(x&8)>>7+(x&f8)>>4
I think.

To put this in perspective, in a plotted scroller with about 20 pixels per character, that's about 25 letters per frame.
That would easily fill the plot area and have time for effects.

2024-07-27 06:28

Repose

Registered: Oct 2010
Posts: 227

Here's the 16x16 char or 128x128 pixel hires code:
;ldy ycoord
;ldx xcoord
lda mul128low,x ;4
sta $fe ;3
lda mul128high,x ;4
sta $ff ;3

lda mask,x ;4
ora ($fe),y ;5
sta ($fe),y ;5
;28
This isn't very fast or much better than a bitmap it seems.

thanks to
https://csdb.dk/forums/?roomid=11&topicid=24359&showallposts=1

2024-07-27 10:37

Jammer

Registered: Nov 2002
Posts: 1336

OMG Got Balls!

2024-07-27 12:54

HCL

Registered: Feb 2003
Posts: 728

Quote:

Does anyone know the record for most pixels plotted per frame?

Oups, that's quite a vague request.. There are many ways to plot pixels and generally speed gets traded against flexibility. Pimp My Snail comes to mind but there are many others.

2024-07-27 13:33

Oswald

Registered: Apr 2002
Posts: 5095

to clr you can just store the calculated address while in the drawing phase in a speedcode that looks like:

sta
sta
sta
sta

each sta clears one dot :)

animated dot sphere records:

- one trick is to use sprites with 1 pixel vertical line in them, change spr xcoo per rasterline to set xcoo of pixel
- you can collect writes with the same ZP hi address into chunks, so you only need to change the lo byte for a number of pixels. (sta (),y)

I guess got balls animated ball uses the fact that many times there is 2 pixels in same byte, and sets them with one write.

2024-08-04 08:00

Repose

Registered: Oct 2010
Posts: 227

Thanks. OMG Got Balls and Pimp my snail have the same code for fullscreen bitmap, with unrolled code for 38 cycles. This is from the plotter of Pimp my snail.

.C:4008  B1 38       LDA ($38),Y ; slowly varying data
.C:400a  9D 00 24    STA $2400,X
.C:400d  BC 00 65    LDY $6500,X
.C:4010  8C 41 3E    STY $3E41 ; $3E47
.C:4013  AA          TAX
.C:4014  BD 00 66    LDA $6600,X
.C:4017  99 00 2B    STA $2B00,Y
.C:401a  A0 1B       LDY #$1B ; $1A
.C:401c  B3 28       LAX ($28),Y
.C:401e  8D 44 3E    STA $3E44 ; $3E4A
 ; 3/4 sinewave at $6400?

I don't quite follow it yet, but I think the points are sorted somehow. That's a good idea. I haven't seen anything yet faster than my idea.

2024-08-04 11:37

Oswald

Registered: Apr 2002
Posts: 5095

4 stores for plotting a dot ? I have no idea what that code does

2024-08-04 14:32

Sparta

Registered: Feb 2017
Posts: 49

Quoting Repose

Thanks. OMG Got Balls and Pimp my snail have the same code for fullscreen bitmap, with unrolled code for 38 cycles. This is from the plotter of Pimp my snail.

.C:4008 B1 38 LDA ($38),Y ; slowly varying data .C:400a 9D 00 24 STA $2400,X .C:400d BC 00 65 LDY $6500,X .C:4010 8C 41 3E STY $3E41 ; $3E47 .C:4013 AA TAX .C:4014 BD 00 66 LDA $6600,X .C:4017 99 00 2B STA $2B00,Y .C:401a A0 1B LDY #$1B ; $1A .C:401c B3 28 LAX ($28),Y .C:401e 8D 44 3E STA $3E44 ; $3E4A ; 3/4 sinewave at $6400?

Just to set things straight, that code snippet is from OMG got balls, and it is far from being the same as Pimp my snail's plotter code. It takes 40 cycles for two screen writes and also preps the erase routine. Hence the four writes. :)

2024-08-04 15:08

Oswald

Registered: Apr 2002
Posts: 5095

ah so ball mirror included, that clears things up

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