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2019-07-22 00:58

Shadow
Account closed

Registered: Apr 2002
Posts: 355

Event id #2846 : The 256b sprite font compo

<Post edited by moderator on 22/7-2019 11:21>

* 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 the letters A-Z should be present and readable.
* 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.).
* The generator code may use ZP and stack (remember that your code is a subroutine that is being called though, so don't destroy the return address!)
* The generator may use memory up to $3fff
* Max three entries per coder
* The deadline for the compo is two months from now, 2019-09-22 at 23:59:59 CET
* Then follows a voting period of two weeks, a snapshot of the CSDb votes at 2019-10-06 at 23:59:59 CET will be the final result. (modedit: fixed date)
* 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

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2019-07-27 01:02

Shadow
Account closed

Registered: Apr 2002
Posts: 355

Quote: I assume its not safe to assume that $2000-$2ffff is filled with anything other than random bytes?

That is correct, my "super-secret-verfier" does fill all areas with crap before running, so if your font doesn't look the same as the normal .PRG when run from that, the entry will be set as out-of-compo until fixed.

2019-08-07 10:25

ChristopherJam

Registered: Aug 2004
Posts: 1378

Is it ok to trash locations $00 and $01?

I can shave two bytes off the entry I'm currently working on if that's legal, and the default viewer doesn't appear to care (I'm on 519b at the moment...)

(edit: I've managed to get down to 513b without changing location $00 after all, and I know that other entries already change $01, but it would be interesting to get a rules clarification anyway :) )

2019-08-07 20:33

Shadow
Account closed

Registered: Apr 2002
Posts: 355

Yeah, I see no reason why you can't trash $00 and $01, I assumed a lot of entries would be switching in the char ROM for example, so that was expected.

2019-08-10 17:08

Mixer

Registered: Apr 2008
Posts: 422

I wanted to put data from page start but the jsr $0900 rule ruined the plan :( -> plan b

2019-08-10 20:02

Digger

Registered: Mar 2005
Posts: 421

@Mixer: True, "generatefont" address ought to be somewhat arbitrary within the page. Can you start at $9ff and read backwards? ;-)

2019-08-19 14:57

Digger

Registered: Mar 2005
Posts: 421

Kernal/BASIC usage is allowed right? Here’s some neat tricks that might be useful http://nurpax.github.io/posts/2019-08-18-dirty-tricks-6502-prog..

2019-08-20 06:38

Oswald

Registered: Apr 2002
Posts: 5017

I'd have preferred to have in the rules that the rom font must be explicitly used. Generating a font entirelly from 256b, and out of the existing ROM one is two totally different beast.

2019-08-20 09:07

ChristopherJam

Registered: Aug 2004
Posts: 1378

That would be quite a different competition, Oswald.

Going by the last few comments on the proposal discussion (cf Proposal - The sprite font compo!), part of the point of this one was to pit the two approaches against each other.

I may yet do a ROM based entry next month, will see how I go for time and spoons.

2019-08-20 21:03

Oswald

Registered: Apr 2002
Posts: 5017

yeah, well next year could have been font generator without using ROM font compo, and this one could have been ROM only. But I was amongst the naysayers, but glad to see creativity finding its way, inspired me too, thinking on something.

2019-08-28 08:51

Digger

Registered: Mar 2005
Posts: 421

Lil’ bit disappointed with no entry from Cruzer though ;-)

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