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2019-07-14 15:56

Shadow
Account closed

Registered: Apr 2002
Posts: 355

Proposal - The sprite font compo!

Last year there was the hugely successful 128b font competition, which had a very good turnout.
Lots of people who could compete since it was pretty simple code, and the result were lots of nice fonts which can be a good tool to have for sizecoding stuff.
It got me thinking about arranging a similar compo, but for sprite fonts!
But before kicking the compo off, I'd like some input on the rules etc.
Here's what I have so far:

* The object of the competition is to generate a sprite-font, in 256 bytes or less code.
* The code should be placed at $0900 and up, but no further than $09ff and must end with an RTS.
* The sprites should be placed at $2000-$2fff, so sprite number $80-$bf.
* 64 sprites are viewed, but it is up to the coder to decide how many he want to generate, but to be considered a font, at least sprite $81-$9b should be readable as the letters A-Z.
* For the other sprites, you can of course generate the appropriate numbers/punctuation characters, or spaceships or whatever, or not generate them at all and spend all your bytes on doing fancier A-Z, it's up to you to decide what will impress the voters most! :)
* Since the code to actually view the sprites would take quite some space, and the competition should not be about that optimizing the viewer code (or who can do the coolest looking viewer) I will provide the code that displays the 64 sprites on screen, it will occupy $0801-$08ff, and will perform a JSR to $0900 where your font generation code should be.
* The viewer has a number of tweakable parameters that are placed on $0810-$0814:
$0810 - $00=Sprites should be singlecolor. $ff=Sprites should be multicolor
$0811 - Bakground and border color.
$0812 - Sprite base color ($d027-$d02e will be set to this)
$0813 - Sprite multicolor1 ($d025 will be set to this)
$0814 - Sprite multicolor2 ($d026 will be set to this)
Simply change these bytes directly in the viewer code (if you compile it) or in the final binary if you use that, they should not be set from you generator code, as this is also not something that should steal your precious space.
* The generator code may *not* depend on A,X,Y holding specific startup values, or memory being initialized to something specific (you may for example not pull data from the viewer code and use etc.).
* Max three entries per coder
* Voting will be done using the CSDb system (yeah, I'm not as cool as lft!)
* No prizes except eternal glory.

Here's the viewer code for Kick Assembler usage, with a place to put your generator code at the end:

.pc =$0801 "Basic Starter"
:BasicUpstart($0820)

.pc=$0810 "Constants"
multicol:
	.byte $00
bgcol:
	.byte $06
sprcol:
	.byte $0e
sprmcol1:
	.byte $00
sprmcol2:
	.byte $00

.pc = $0820 "Code"
		sei
		lda multicol
		sta $d01c
		lda bgcol
		sta $d020
		sta $d021
		lda sprmcol1
		sta $d025
		lda sprmcol2
		sta $d026
		lda sprcol
		ldx #$07
!loop:		
		sta $d027,x
		dex
		bpl !loop-
		ldx #$00
		lda #$20
!loop:		
		sta $0400,x
		sta $0500,x
		sta $0600,x
		sta $0700,x
		inx
		bne !loop-
		lda #$ff
		sta $d015
		lda #$80
		sta $d010
		ldx #$07
		ldy #$00
		lda #$18+44
!loop:	
		sta $d000,y
		clc
		adc #29
		iny
		iny
		dex
		bpl !loop-
		jsr generatefont
		lda #$35
		sta $01
mainloop:
		lda #$2f
		sta ycoord
		lda #$80
		sta spridx
yloop:
		lda ycoord
!wait:
		cmp $d012
		bne !wait-		
		clc
		adc #4
		ldx #$07
		ldy #$00		
!loop:		
		sta $d001,y
		iny
		iny
		dex
		bpl !loop-
		ldx #$00
		ldy spridx		
!loop:		
		tya
		sta $07f8,x
		iny
		inx
		cpx #8
		bne !loop-
		clc
		lda spridx
		adc #8		
		sta spridx
		lda ycoord
		adc #25
		sta ycoord
		cmp #$2f+8*25
		bne yloop
		jmp mainloop

ycoord:
		.byte 0	
spridx:
		.byte 0

.pc=$0900 "Font generation code"	
generatefont:
		rts

Yes, code is neither pretty nor optimal, but that's not the point here, the pretty code should be written by YOU! :D

If you prefer some other assembler, here's the prebuilt binary for the $0801-$08ff portion:
sprite_font_view_base.prg

Here are some simple examples I've done to prove that it actually works:
Sprites using ROM font scaled to 3x3 pixel size. $0810 params set to : $00,$06,$0e,$00,$00
example1.prg

Exact same font but with multicolor params set (works this way as well!) $0810 params set to : $ff,$0b,$0c,$0f,$0f
example2.prg

So does these rules make sense?
I've been thinking a lot about the 256 byte limit, but I think it should be large enough to do some interesting things. My naive implementation of scaling up the ROM font is $9a bytes, which leaves plenty of space for actually tweaking the font, and I am sure some smart coders can do it in way less space.
I've been thinking on the possibility of generating a font from scratch using partial segments, not sure yet if it's doable in 256 bytes.
Unless someone has some compelling arguments, the 256 byte limit stands.
What's an appropriate time for such an event? Two months? Three?

And finally, does this seem like fun? Anyone think they will participate? :)

... 20 posts hidden. Click here to view all posts....

2019-07-20 20:18

ChristopherJam

Registered: Aug 2004
Posts: 1409

Hrm. I get an undefined symbol error if I don't? What am I missing?

(note that each file exports one symbol and imports another..)

2019-07-20 20:32

JackAsser

Registered: Jun 2002
Posts: 2014

Quote: Hrm. I get an undefined symbol error if I don't? What am I missing?

(note that each file exports one symbol and imports another..)

-U on the assembler flags (also why AFLAGS on the linker command?).

"-U Mark unresolved symbols as import"

This also means that really unresolved symbols will only generate errors during the linking phase, just like normal compilers.

2019-07-20 20:49

ChristopherJam

Registered: Aug 2004
Posts: 1409

Ah, nice. Though, I do like to be explicit about such things these days.
(AFLAGS thing is just cruft, I should fix that)

Ok, back to compo talk now :)

2019-07-21 00:11

Compyx

Registered: Jan 2005
Posts: 631

I think the 256 byte limit could be too constricting, resulting in a lot of CHARGEN copies with very little 'art' applied.

2019-07-21 01:28

Shadow
Account closed

Registered: Apr 2002
Posts: 355

Thanks for all the feedback, I'll do some minor changes to the rules based on some of all your suggestions, and set up a proper event later today probably.

We'll simply have to see if the concerns that 256 bytes is not enough to do anything interesting turns out to be true or not, but I have high faith in the C64 scene coders! ;)

2019-07-21 04:03

ws

Registered: Apr 2012
Posts: 251

One more detail: will the viewer display all the sprites gapless? Or will there be spaces between them?

2019-07-21 12:21

Shadow
Account closed

Registered: Apr 2002
Posts: 355

Quote: One more detail: will the viewer display all the sprites gapless? Or will there be spaces between them?

There's a few pixels of space between them when displayed, so the full 24x21 can be used without it looking weird.

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