Working on a space invaders game...

emkay · June 13, 2006

and now I understand why every line will need its own LMS instruction...

but .. hmm damn, i need to think on how to implement the march downward now...

-Thom

Empty Lines (Without DMA)?

Adding empty lines on the top and removing them on the bottom looks like vertical scrolling aswell.

tschak909 · June 13, 2006

as for a background, I was... _thinking_ of using the player/missile graphics to do this. to do some simple stuff like a planetoid and some stars....... this will probably completely relegate playfield graphics for the other stuff... but.. oh crap.. the horizontal/vertical smooth scrolling is gonna freak everything out, the bullet is gonna zig zag all over the place... hmm, maybe i could do a correction in the character set to have 8 character states to correct for the .... crap.. that won't take care of the vertical state either.. hmm damn, i am going to have to think about this, because I want to try to implement a working background, and missiles, and falling powerups.. i will probably have to use players in a most creative way..... hummm...

emkay · June 13, 2006

but .. hmm damn, i need to think on how to implement the march downward now...

-Thom

Here you may use the full 48 char-width so you can scroll for an 8 chars width "for free"

Rybags · June 13, 2006

Just have a DLIST with LMS for the lines the invaders occupy.

Obviously, the H-scroll takes place over a wide range - probably best to seperate each line by 128 bytes. Some wastage occurs, but the advantage is that all you have to do is OR in the low 7 bits of the address to each LMS operand.

Playing about with blank lines could be the way to go - alternatively adjusting the LMS addresses acheives the downward march as well.

1 player can double as the ship, and the shot. Leaving 7 other PMs for enemy shots (more than enough).

Typically, you'd probably only have 1 powerup visible, so that's one player that gets "re-assigned" usage-wise for a time.

For multi-shot, you could just re-use the missile - just have some logic in the code that tells the DLI routine where the H-pos change has to occur. But, you also have to factor in your VScroll value.

Probably the best method is to have one DLI routine, have all colour and positional changes stored in tables for the DLI to lookup.

tschak909 · June 13, 2006

am curious, if I am doing development in mac/65 and am loading the result from DOS, do I have to use the memlo as reported by SIZE? or can I actually cram stuff lower in memory? how low can I go?

-Thom

tschak909 · June 15, 2006

Working currently on the player graphic. I wanted the player to be able to have a temporary shield, so I designed two definite states, with and without shields, which will be rotated with the character set providing the animation. I am also reorganising the display list to something more proper for horizontal scrolling. I will be adding in the most basic player movement next.

-Thom

Rybags · June 15, 2006

You're better off using ATASM or one of the PC-based Assemblers, then you don't have to worry about clobbering your source code.

Then, just load the resulting XEX from DOS (or run autoexec from the emulator).

With MAC/65 you should stay well away from MEMLO. Also, extra memory is used during assembly. Effectively, you are in danger anywhere under about $3000 if using DOS.

Page 6 is fine, not that you fit anything significant there.

I'm doing my development in stages... just assemble everything to run around $4000-$6000, then do the shuffling about when everythings ready to put together.

Re: Display list. Maybe define it like this:

nn Blank lines (top of screen)

LMS xxxx MODE 2 (score display)

nn Blank lines (gap)

LMS xxxx MODE 4 HSCROL (UFO)

3 Blank

JUMP DLIST nnnn

repeat the above sequence 20 or so times. The JUMP operand just points to the next instruction.

Then, you just have to store into the JUMP instruction where you want the invaders to start.

Invaders DLIST:

HSCROL MODE 2 LMS nnnn (repeat xx times)

For the remainder of the DLIST, have 4 blank lines with DLI.

At this point, the DLI routine checks VCOUNT. When VCOUNT is where the ship should be, load ANTICs DLIST pointer to point to the ship's DLIST entry:

HSCROL MODE 4 LMS nnnn

JBV nnnn

tschak909 · June 15, 2006

Thanks for the tip on atasm, Rybags! I've been trying all the various combinations of assemblers etc and I think this one will be a perfect fit for me!

-Thom

Rybags · June 15, 2006

invdlist.zip

Sample program in Atari BASIC, with technique I described + DLI.

Ignore the jitters, it's just because it's BASIC updating pointers (ie - slow, plus it should be done in VBI).

It illustrates the technique I described above. The DLI routine checks VCOUNT and when it's at a certain point, forces the DLIST pointer to display the last line in Mode 2.

Yellow lines are just colour change so you can see where the DLIs are being executed.

Use a joystick - move left/right to move the central window of the display up and down.

tschak909 · June 15, 2006

Thanks, I am looking at it right now! :-)

-Thom

tschak909 · June 21, 2006

Wanted to let you guys know, that I am still working on the game. I've been in the process of re-building it in ATASM on the Linux side, instead of using MAC/65 inside the Atari 800 itself. I got tired of being squinched into 40 columns.

My current goal right now, is to refactor and get the invaders display working again, then work on getting the bottom half of the display working, and get player movement working.

I have put together a more comprehensive set of system equates, merging information from the Programmers Card on De Re Atari, and the ATARI OS SYSTEM EQUATES file, from an internal Atari document dated March of 1982. I am modifying the memory map chart that I provided earlier, to more accurately reflect what's being used in the zero page, but it is nice to know that the top 128 bytes of page 0 are available "for user programs"

I have attached a picture of a crater design that I am working on for the bottom half of the background.

Talk to you guys soon,

-Thom

<-- doing a sketch of the bottom moon graphics

tjb · June 21, 2006

<-- doing a sketch of the bottom moon graphics

I like it!

-tjb

tschak909 · June 29, 2006

I've done the first little test of some vertical scrolling techniques using a moving ANTIC JMP instruction, so far it works, i just need to alter the counter on the up cycle slightly, but one question.. how do I make the scrolling completely smooth, with no jumps?

-Thom

Source: t01vscrl.zip

;

; TEST PROGRAM TO TRY MY DISPLAY LIST THEORY.

;

; NOTES

;

; 5 INVADERS LINES OF 8 PIXELS HIGH

; 2 BLANK LINES BETWEEN EACH SEGMENT

;

; USING ANTIC MODE 2 TO SEE THE LINE DIVISIONS

;

.INCLUDE atariequ.asm

UPCTRL = $80 ; UP LINE COUNTER

UPCTRH = $81 ;

DNCTRL = $82 ; DOWN LINE COUNTER

DNCTRH = $83 ;

UPDOWN = $84 ; GOING UP OR DOWN?

*=$2000

JMP START

;

; DISPLAY LIST

;

DLIST .BYTE $70 ; 3 BLANK 8-LINES

.BYTE $70 ; FOR THE

.BYTE $70 ; BORDER

UPJMP .BYTE $01,<UPBOT,>UPBOT

UPBLNK .BYTE $00 ; 1 BLANK LINE

.BYTE $00 ; 1 BLANK LINE

UPBOT .BYTE $00 ; 1 BLANK LINE

.BYTE $55,$00,$49 ; BONUS DISPLAY

.BYTE $40 ; 5 BLANK LINES

.BYTE $52,$00,$50 ;

.BYTE $20 ; 3 BLANK LINES

.BYTE $52,$00,$51 ;

.BYTE $20 ;

.BYTE $52,$00,$52 ;

.BYTE $20 ;

.BYTE $52,$00,$53 ;

.BYTE $20 ;

.BYTE $52,$00,$54 ;

DNJMP .BYTE $01,<DNTOP,>DNTOP ; JUMP INSTRUCTION FOR MIDDLE OF SCREEN

DNTOP .BYTE $00 ; 1 BLANK LINE

.BYTE $00 ; 1 BLANK LINE

DNBOT .BYTE $00 ; 1 BLANK LINE

.BYTE $41,<DLIST,>DLIST ; JUMP BACK TO BEGINNING OF DLIST AT VBLANK

;

; MAIN PROGRAM

;

START CLD

SCTR LDA #<UPBOT ; SET INITIAL COUNTERS

STA UPCTRL ;

LDA #>UPBOT ;

STA UPCTRH ;

LDA #<DNTOP ;

STA DNCTRL ;

LDA #>DNTOP ;

STA DNCTRH ;

LDA #$01 ;

STA UPDOWN ;

SDMA LDA #$3D ;

STA SDMCTL ; SET UP PLAYFIELD

SDLS LDA #<DLIST ; SET UP DISPLAY LIST

STA SDLSTL ;

LDA #>DLIST ;

STA SDLSTL+1 ;

SVBI LDA #$06 ; IMMEDIATE VBI

LDY #$00 ;

LDX #$06 ;

JSR SETVBV ;

LOOP JMP LOOP

;

; VBI ROUTINE

;

*=$0600

VBI TXA ; PUSH EVERYTHING ONTO STACK

PHA ;

TYA ;

PHA ;

LDA #67

STA COLOR2

LDA RTCLOK+2 ; GRAB REALTIME CLOCK VAL

AND #$0 ; EIGHT VBI

BNE VBDON ; SKIP IF THIS ISN'T OUR TIME.

LDA #$00 ; ARE WE GOING UP OR DOWN?

CMP UPDOWN ;

BEQ GOUP ;

GODOWN LDA #39

STA 712

DEC UPCTRL ; UPDATE COUNTERS FOR THE MOVE.

INC DNCTRL ;

LDA UPCTRL ;

CLC ;

ADC <UPJMP ; ADD THE LO BYTE OFFSET OF THE JMP INSTRUCTION

STA UPJMP+1 ; UPDATE THE DLIST

LDA DNCTRL ;

CLC ;

ADC <DNJMP ; AND AGAIN....

STA DNJMP+1 ; UPDATE THE DLIST

LDA #$00 ; 124 LINES PASSED?

CMP DNCTRL

BEQ SETUP ; FLIP THE FLAG TO UP

JMP VBDON

GOUP LDA #23

STA 712

INC UPCTRL ;

DEC DNCTRL ;

LDA UPCTRL ;

CLC ;

ADC <UPJMP ;

STA UPJMP+1 ;

LDA DNCTRL ;

CLC ;

ADC <DNJMP ;

STA DNJMP+1 ;

LDA #$00 ;

CMP UPCTRL ;

BEQ SETDN ;

JMP VBDON

SETUP LDA #$00 ; SET FLAG TO UP

STA UPDOWN ;

JMP VBDON ;

SETDN LDA #$01 ; SET FLAG TO DOWN

STA UPDOWN ;

JMP VBDON ;

VBDON PLA ; TAKE EVERYTHING OFF OF STACK

TAY ;

PLA ;

TAX ;

JMP SYSVBV ; AND JUMP TO THE DEFERRED VBI VECTOR

;

; SCREEN MEMORY

;

*=$4900

.SBYTE " () "; BONUS DISPLAY

.SBYTE " "

*=$5000

.SBYTE " !! !! !! !! !! !! !! !! "; INVADERS LINE 1

.SBYTE " "

*=$5100

.SBYTE " @@ @@ @@ @@ @@ @@ @@ @@ "; INVADERS LINE 2

.SBYTE " "

*=$5200

.SBYTE " ## ## ## ## ## ## ## ## "; INVADERS LINE 3

.SBYTE " "

*=$5300

.SBYTE " $$ $$ $$ $$ $$ $$ $$ $$ "; INVADERS LINE 4

.SBYTE " "

*=$5400

.SBYTE " %% %% %% %% %% %% %% %% "; INVADERS LINE 5

.SBYTE " "

.SBYTE " &

Rybags · June 29, 2006

I think the apparent jumpiness is just the emulator... I did another VBI that just did INC $230, LDA $230, AND #$7F, STA $230 and it looked a little stuttered as well.

No need to push/restore registers on the stack, it's already being done by the OS.

xxl · June 29, 2006

and now I understand why every line will need its own LMS instruction...

but .. hmm damn, i need to think on how to implement the march downward now...

inser blank lines into dlisplay list

if you want 'march downward' then replace 1 blank line into 8 blank lines

color will be unchanged if you use dli

tschak909 · July 2, 2006

Greetings all,

Am nearing the final revision of the playfield layout that I want. I thought I would paste a screenshot so that everyone here could see what I am working on. I have posted two shots, one with NTSC emulation, and one without, it's giving me a reference as to what I need to correct, graphics-wise.

(yes, I am aware of the hanging pixel on the bottom invaders, I am using it as a special reference right now for a bounding box).

<-- with NTSC emulation.

<-- without NTSC emulation.

t05scrtest2.zip <-- the screen test source code.

Some further notes:

I will be using players/missiles from this point on, to provide all the non-scrolling elements (this includes all the background elements, player missiles, the breakout ball, and any additional player missile states not covered here.. I will be needing to do some serious creative thinking to get all this working together....

but knowing that:

I need a gun for the player

I need a gun for the enemies (maybe a limit of two shooting at once.)

I need a player for the breakout ball when it enters breakout mode

at the very least,

what do i have left over to draw background elements? (thinking)

-Thom

Edited July 2, 2006 by tschak909

emkay · July 3, 2006

at the very least,

what do i have left over to draw background elements? (thinking)

What about NOT using the scroll register? You would get the same effect, with the "ROL/ROR" technique on the visual chars. And doing a charmovent at all?

One change per charmode line moves all "ships" in the same line.

You can set a nice background then, and/or you can do shots via charmovement haveing the PM Fere for an additional underlay....

... just a suggestion

tschak909 · July 3, 2006

at the very least,

what do i have left over to draw background elements? (thinking)

What about NOT using the scroll register? You would get the same effect, with the "ROL/ROR" technique on the visual chars. And doing a charmovent at all?

One change per charmode line moves all "ships" in the same line.

You can set a nice background then, and/or you can do shots via charmovement haveing the PM Fere for an additional underlay....

... just a suggestion

What do you mean exactly? can you describe the technique to me in more detail? I'm not wanting to sacrifice a smooth scroll, but I don't have all the character set space in the world, either, to draw every concievable smooth scroll position against the background.

I guess I just need more clarification on you as to what you mean?

-Thom

Ghost... · July 3, 2006

at the very least,

what do i have left over to draw background elements? (thinking)

What about NOT using the scroll register? You would get the same effect, with the "ROL/ROR" technique on the visual chars. And doing a charmovent at all?

One change per charmode line moves all "ships" in the same line.

You can set a nice background then, and/or you can do shots via charmovement haveing the PM Fere for an additional underlay....

... just a suggestion

What do you mean exactly? can you describe the technique to me in more detail? I'm not wanting to sacrifice a smooth scroll, but I don't have all the character set space in the world, either, to draw every concievable smooth scroll position against the background.

I guess I just need more clarification on you as to what you mean?

-Thom

Lets say your alien consists of 2 chars (XY) on screen.

Then spend one more => 3 Chars (XYZ)

Preshift the bytes of the chars with ROR ( carry => 7. bit and 0. bit => carry):

CLC

lda X (byte 1)

ROR

sta ..memx_animation1

lda Y (byte 1)

ROR

sta memy_animation1

lda Z (byte 1)

ROR

sta memz_animation1

lda X (byte 2)

ROR

..for all the 8 rows of the char

..8 times graphics 0 or 2*4 times for antic 4

To display a certain animation step copy the pre-shifted chars (animation_n) into the character mem.

emkay · July 4, 2006

Lets say your alien consists of 2 chars (XY) on screen.

Then spend one more => 3 Chars (XYZ)

Preshift the bytes of the chars with ROR ( carry => 7. bit and 0. bit => carry):

CLC

lda X (byte 1)

ROR

sta ..memx_animation1

lda Y (byte 1)

ROR

sta memy_animation1

lda Z (byte 1)

ROR

sta memz_animation1

lda X (byte 2)

ROR

..for all the 8 rows of the char

..8 times graphics 0 or 2*4 times for antic 4

To display a certain animation step copy the pre-shifted chars (animation_n) into the character mem.

Exactly.

A "faster" way may be to use all different animation steps, inlcuding the "Bit"-offset/vertical movement pre-shifted, to save cpu time with cost of memory.

Let's say you want to have a real smooth and independent animation with four steps.

You'd need 4 steps * 4 horizontal positions * 3 Chars * 4 different ships * 8 Bytes:

It would take 1536 Bytes of Data.

Without the scrolling, you may use the "playfied" for shots" and the PMg can be used for some Background graphics.

Rybags · July 4, 2006

The approach you take should reflect what you want in the background.

If all you want is a couple of dozen single pixel "stars", then the best approach would be to just keep your current scroll technique and split a PMG.

If you wanted something more complex (e.g. moon, moving stars etc), then treat the background objects as software sprites.

Draw those sprites under the invaders taking into consideration memory offsets and scroll values so that they appear stationary.

As such, you would need preshifted definitions (4x) for each background Chr. Have AND masks available for the invader characters.

Mix the data together, use pre-reserved characters for the resultant. Have a buffer to restore in between scroll / re-render phase.

tschak909 · July 10, 2006

Well guys, after a lot of debugging, I have the horizontal scrolling motion working properly.. I have sped it up so that it could be seen.

I have attached the code below, but basically my approach is this:

* use the main line code to set global states, go left? go right?

* use the VBI to update actions that need to happen per frame, update the zero page locations for current HSCROL and LMS positions.

* use the DLI to update the HSCROL registers appropriately.

it's coming along, bit by bit... now it's time to put in the first bits of player code

(and no, this is NOT a final on the motion... I will be tweaking the motions using a lot of hand tables to give the illusion of speeding up and slowing down...)

what do you guys think?

-Thom

T06PLMOT.zip

Plastron · July 10, 2006

Hi,

For the ground at the bottom if you make the last screen look the same as the first screen when you jump back to the begining it will not jump as it does now. This is how it is done in Plastron and the Metro Cross demo so it looks like continuos scrolling.

Andy

Heaven/TQA · July 10, 2006

looks good!

tschak909 · July 11, 2006

muahahahahaha, THEY LIVE!

After combining the horizontal and vertical scrolling techniques from the other code tests, I've been able to make smooth scrolling produce a nice silky smooth march both horizontally, and vertically.. the march ends once the invaders have marched all the way to the bottom of the screen.....

Next up! Player motion! (the final animated character sets and motion vectors will come later after I have implemented more of the basic stuff.)

-Thom

T07INVMH.zip

Working on a space invaders game...

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