My experiments with Atari 7800

[Eagle]

Maria 160B mode for background and sprites

GFX from A8 version by @Tezz Vega and @tebe

Sprites version by @TIX colored by me to 160B

Also I did conversion test of G2F picture by Odyn1ec

 

 

 

 

[+Defender_2600]

Great demo! 

 

And on the 7800, the background of Bomb Jack can be very close to the arcade version. Here is an example from my old 160B archive. I also added a third green color to enhance the trees.

 

 

 

 

 

Edited February 23, 2023 by Defender_2600

[TIX]

Hey @Eagle,

 

That's a very promising demo !!

 

The set of Bomb Jack sprites are from an old attempt to hack/replace the ugly C64 sprites for the A8 port.

I'm sure we can do MUCH better for the 7800 when time comes 😉

[Eagle]

@Defender_2600 unfortunately I can use only 128px for background.

@TIX BJ is 3rd or 4th on my list TODO, so plenty of time left.

 

Today next test, Polish classic game FRED

ps. sorry for background, I was to lazy today  

 

 

 

 

edit: wider background

 

 

 

 

Edited February 23, 2023 by Eagle

[+Defender_2600]

46 minutes ago, Eagle said:

@Defender_2600 unfortunately I can use only 128px for background.

 

When you're ready to work on Bomb Jack, let me know. I'll get you the background graphics of all levels in 128 pixels.

 

[+Defender_2600]

2 hours ago, Eagle said:

Today next test, Polish classic game FRED

 

I love the original black background, it brings out the detail of the graphics and makes them more solid. The new colors are beautiful.

 

[Revontuli]

9 hours ago, Eagle said:

Today next test, Polish classic game FRED

Impressive scrolling!  

 

While I have a few ideas on how to have different elements of a scrolling background have different palettes, my own scrolling engine assumes a single palette for the whole thing (or at least per zone).  I'm curious as to the approach/limitations you have for system, and how many cycles you have left!

 

[Eagle]

Thanks @Revontuli

Scroll is using 126 cycles per each line. This is direct mode 160A (21 tiles 8px wide per line)

So around 1000 for full screen plus few hundreds every 8 frame for updating the right side of the screen.

DMA usage is not bad for a screen with no background. I would say 200 Maria cycles on average per line (empty tiles are pointing DMA holes saving cycles)

With background layer DMA usage is very close to Maria limits. (this was just done as prof of concept) 

But in Fred, all the animations and movements of the enemies were done on the chars, so I'm sure it could work well.

I'll give some code example later.

 

[+karri]

1 hour ago, Eagle said:

This is direct mode 160A (21 tiles 8px wide per line)

With just one 8px tile that is not on screen I assume that you draw the new content on this column when it is hidden to avoid the flicker. Correct?

[Eagle]

@karri yes

 

There is so many variants, so let me explain easiest one. 

Scrolling screen to the left (like Fred, Mario Bros, etc.)

Mode 160A, tiles 16x16, each tile can have pallet 0-7

 

For one line Display list example in MADS (# is counter in mads, :21 repeat line 21 times and increase counter)

 

line0    :21 .byte <TileFred,$1e,>TileFred,#*8

 

Mads will generate 21 headers 4 bytes each

It will look like this

 

line0       
			.byte <TileFred,$1e,>TileFred,0
  			.byte <TileFred,$1e,>TileFred,8
  			.byte <TileFred,$1e,>TileFred,16
  			.byte <TileFred,$1e,>TileFred,24
  			..........
  			.byte <TileFred,$1e,>TileFred,160	;tile 21 outside visible screen - X position = 160
  

 

 

to scroll left you need decrease Xpos for every tile (4th byte of every header)

Again in MADS will look like this

 

    :21 dec line0+3+[#*4]

 

this will generate 21 lines 

 

		dec line0+3+0
		dec line0+3+4
		dec line0+3+8
		dec line0+3+12
		dec line0+3+16
		...............
		dec line0+3+80

 

then you check all xpos in line0 and update them

 

chceck_for_update_column
	ldx #$00
loop 
	lda line0+3,x
	cmp #$F8	;or $f9 depends when you'r checking
	beq update_column
	inx
	inx
	inx
	inx
	cpx #21*4	;21 headers
	bne loop
; no time for update tiles
	rts

update_column
;in X you have column for every line
;store on zeropage or somwhere

	lda #160	;change full column xpos to outside screen on the right side
	sta line0+3,x
	sta line1+3,x
	sta line2+3,x
	...........
	sta line12+3,x
;
;update lsb,msb and colour for new tiles on the right side
; if tiles is empty/background set msb=$F0 to holey DMA
; for saving cycles you don't need update colour and lsb then as well

	lda #<lsb_new_tile
	sta line0+0,x  
	lda #>msb_new_tile
	sta line0+2,x
	lda #colour_and_width_new_tile
	sta line0+1,x
;
	lda #<lsb_new_tile
	sta line1+0,x  
	lda #>msb_new_tile
	sta line1+2,x
	lda #colour_and_width_new_tile
	sta line1+1,x
; repeat this again for next lines
;
;

 

 

I hope it helps. 

 

edit: changed rows to columns (sorry for confusion) 

Edited February 24, 2023 by Eagle

[+karri]

Yes, I got it.

 

Obviously I made one mistake in Wizzy. I update the tiles too late when they are in the viewport.

 

But I might do this fine tuning later when I know how much resources are left.

 

Currently I do my displaylist modifications during the screen blank time.

So I scroll just 7 zones during the first irq, and the remaining 7 during the next irq.

This housekeeping with irq's allow me to run sfx sound effects and vgm player

using irq's as well.

; The horizontal scrolls need a number of lines to scroll
; It will scroll scrri lines per irq and change the _scrptr
; and decrement the _scrri
.macro addoff off
	ldy	#4*off
	lda	(_scrptr),y
	clc
	adc	#8
	sta	(_scrptr),y
.endmacro

scrollright:
	lda	_scrri
	bne	@L1
	clc		; Slot not used
	rts
@L1:	
	addoff 0
	addoff 1
	addoff 2
	addoff 3
	addoff 4
	addoff 5
	addoff 6
	addoff 7
	addoff 8
	addoff 9
	addoff 10
	lda	_scrptr
	clc
	adc	_rowoff
	sta	_scrptr
	bcc	@L2
	inc	_scrptr+1
@L2:	dec	_scrri
	lda	_scrri
	bne	@L1
	sec
	rts

 

The vertical scroll was easier to do.

.macro movdll from, to
	lda	_dll+1+3*from
	sta	_dll+1+3*to
	lda	_dll+2+3*from
	sta	_dll+2+3*to
.endmacro

scrolldll:
 	; Push first pointer on stack
	lda	_dll+3*3+1
	pha
	lda	_dll+3*3+2
	pha
	movdll 4, 3
	movdll 5, 4
	movdll 6, 5
	movdll 7, 6
	movdll 8, 7
	movdll 9, 8
	movdll 10, 9
	movdll 11, 10
	movdll 12, 11
	movdll 13, 12
	movdll 14, 13
	movdll 15, 14
	movdll 16, 15
	pla
	sta	_dll+3*16+2
	pla
	sta	_dll+3*16+1
	lda	#$00
	sta	_scrup
	sec
	rts		; Slot used already
endscr:
	clc		; Slot not used
	rts

 

I realized that this does not make much sense without the main program that uses the irq.

 

	rowoff = sizeof(Zone);
	if (left) {
		// Move scenery right in two parts
		// to reduce load during flyback
		scrptr = &bgzones[0].extra[0].hpos;
		scrri = 7;
		while (scrri)
			;
		scrptr = &bgzones[7].extra[0].hpos;
		scrri = SCREEN_HEIGHT - 7;
		while (scrri)
			;

 

PS. I am dreaming on visiting Silly Ventures in August. With a playable version of Wizzy.

[Eagle]

LZSS16 player v0.1 for Pokey

NTSC friendly  

 

LZSS16 player - emulator link

LZSS16player.a78

Edited February 25, 2023 by Eagle

[+karri]

I like the bass instrument at the end of the tune.

 

Is this a VGM player for Pokey using LZSS compression?

[Eagle]

No is LZSS player, it's little bit different.

I published source code on AArea discord and we working on it.

I will publish here later when is don, so everyone can make cart with any Pokey music he want.

 

Below few old ones (pal only)

 

BombJack by Miker

 

BubbleBobble

 

Easter by Miker

 

Flimbo by Miker

 

Arabic

 

Bubble Shooter

 

Edited February 27, 2023 by Eagle

[SlidellMan]

That Bomb Jack demo makes it look like he ended up in System Shock, and excellent job on the FRED demo. Eagle, Karri, excellent job on the assembly code.

[Eagle]

Stress test of my latest sprite engine 

Theoretically I can use up to 100 sprites on screen.

[+mksmith]

Brilliant as usual mate!! A fun game too!

[+Stephen]

3 hours ago, Eagle said:

Stress test of my latest sprite engine 

Theoretically I can use up to 100 sprites on screen.

Fantastic!  That's quite impressive.

[Eagle]

12 hours ago, Stephen said:

Fantastic!  That's quite impressive.

Not really, this is just my old code from A800. 

Title is made in G2F by Vidol, and have only 7 colours when I'm using 13 (160B)

Game graphics is from C64, background will be in 4 colours, but bottom it's 25 in 160B (I'm hardly using few for now)

Will se how full gameplay will work then I may decide to put extra background layer to make parallax effect.

 

I'm attaching one of the latest version for A8. 

For Altira you have to go to System>Configure system>Memory>Power-up-pattern>Cleared (I didn't clear memory under OS)

 

Spoiler

Please do not put this on A8 forum  

 

SWruchome.xex

[+Stephen]

Very cool - I like the debug output being displayed.  Can I ask - how do you calculate the framerate (determine if object processing takes > 1 frame)?

[Eagle]

I do not…. This is just text  

[SlidellMan]

That Silk Worm demo is most impressive, Eagle.

[+saxmeister]

Such great and inspiring work. I love to see this old system in the hands of a talented programmer just to see what she can do!

[Eagle]

Small update

Collisions, hitting, explosions, enemies patterns...

 

 

[Eagle]

Just few enemies left to add.

Weapon up, bottom scroll slow down.

Every object in code has his own colour/trajectory/energy level et.

Need to redraw some gfx, will try new level tomorrow and add jeep logic (it's done just need copy/paste from my old code)

 

Spoiler

most of the code should be done by the next week