Pitfall

[kieranhj]

I've managed to download the book Racing the Beam and according to page 35 the TIA offers two number-size registers NUSIZ0 and NUSIZ1 to allow the placement of the same sprites on screen (it's how they did Space Invaders)

So I've got some reading to do tonight

If you want some even more light reading, then this is a HTML version of the defacto Stella Programmer's Guide from 1979!

EDIT: PS. This is looking great! Keep up the good work.

[fizgog]

I've managed to download the book Racing the Beam and according to page 35 the TIA offers two number-size registers NUSIZ0 and NUSIZ1 to allow the placement of the same sprites on screen (it's how they did Space Invaders)

So I've got some reading to do tonight

If you want some even more light reading, then this is a HTML version of the defacto Stella Programmer's Guide from 1979!

EDIT: PS. This is looking great! Keep up the good work.

Thanks Kieran,

I'll look forward to reading this document

[fizgog]

After delving into the Atari TIA I’ve found that the NUSIZ contains the following: -

Code: Select all

; ATARI 2600 NUSIZ
000 - 1 copy
001 - 2 copies - close
010 - 2 copies - med
011 - 3 copies - close
100 - 2 copies - wide
101 - double size player
110 - 3 copies medium
111 - quad sized player

We don't care about double and quad sized player sprites for Pitfall so we can ignore these

if the distance between sprites are 8 - close, 16 medium and 32 wide (will need double checking) we can then set up the following contants

Code: Select all

; 8, 16 and 32 distance
ONE_COPY.            = #$00  ; 00000001 - 1 copy                                    
TWO_COPIES.          = #$0A  ; 00001010 - 2 copies                                
THREE_COPIES.        = #$0B  ; 00001011 - 3 copies close                      
TWO_COPIES_MEDIUM    = #$12  ; 00010010 - 2 copies medium                 
THREE_COPIES_MEDIUM  = #$13  ; 00010011 - 3 copies medium                 
TWO_COPIES_WIDE      = #$22  ; 00100010 - 2 copies wide           

Then we can use the following to extract the info we need

AND #$03 - gets the number of copies to plot
AND #$38 - gets the distance between sprites in pixels

NB On the otherhand if the distance is 16, 32 and 64 then we can shift bits 6,5,4 left by one and then use AND #$70 instead to get the distance

We can then create a table to store the objects copies and distances with the following: -

Code: Select all

; Max 12 objects
.Object_NUSIZ_Table
EQUB ONE_COPY
EQUB TWO_COPIES
EQUB TWO_COPIES_WIDE
EQUB THREE_COPIES_MEDIUM
EQUB ONE_COPY
EQUB THREE_COPIES
EQUB ONE_COPY
EQUB ONE_COPY
EQUB ONE_COPY
EQUB ONE_COPY
EQUB ONE_COPY
EQUB ONE_COPY

and then something like the following: -

Code: Select all

.UpdateObject
    LDX objectType                   
    LDA Object_NUSIZ_Table,X
    STA result
           
    AND #$03    ; get number of copies
    TAX         ; store into X
    LDA result     
    AND #$38 : STA distance
           
.loop  
    JSR UpdateObjectSprite
           
    LDA object_xpos : CLC : ADC distance : STA object_xpos
    DEX
    BNE loop
           
.exit
    RTS

PS All of the above has not been tested as I don't have access to my development machine so may be rubbish

[fizgog]

Code needed a couple of tweaks, but in general it seemed to work

This constant should of been 1 not 0 which was a typo

Code: Select all

ONE_COPY   = #$01  ; 00000001 - 1 copy   

and I used AND #$07 to get bits 123 and AND #$F8 to get bits 45678

I still need to look at how to handle the sprites going off the screen


https://youtu.be/zDUG57gkmkw

[fizgog]

Managed to add the three animated crocodiles last night, no pond though

https://youtu.be/y_YYZMrmQwo

[tricky]

David Crane (the author of Pitfall) presented his postmortem of Pitfall at GDC 2011 and it is available for free in their GDCVault section.
https://www.gdcvault.com/play/1014632/C ... em-PITFALL
This also includes quite a bit of background on the 2600.

[fizgog]

David Crane (the author of Pitfall) presented his postmortem of Pitfall at GDC 2011 and it is available for free in their GDCVault section.
https://www.gdcvault.com/play/1014632/C ... em-PITFALL
This also includes quite a bit of background on the 2600.

Thanks that was a good presentation by David Crane

[fizgog]

It's been way too hot to code at night, but I did end up deciding to rewrite the sprite plotting code from scratch.

Implemented Mode 2 masking and erasing, as using the previous EOR method only gave me a few colours to play with, now I have the use of 16

Added code to allow player to go in between the holes

https://youtu.be/RsxHNKGO1AA

[TobyLobster]

Nice - it's looking good!

[lurkio]

Love to see the progress on this game! Great work!

[Beebson]

Partly hidden Harry looks nice!

[marcusjambler]

Looking very good Fizgog

[Rob_hawk]

Looks like the hard work Sprite rewrite has paid off - looks super

[fizgog]

Added sprite clipping to animated logs

https://youtu.be/nVQlViHTBc4

[FourthStone]

This is coming along great, please keep the posting updates to progress when possible

I'd be interested to know if you're going to follow the same level design logic as the original using one byte to define the screen layout for the entire game along with some logic that decodes it and allows consistent travel to and from each level including the underground shortcuts.

It was described in the post-mortem video by the creator David Crane and I found a nice write up here:
https://evoniuk.github.io/posts/pitfall.html

[fizgog]

This is coming along great, please keep the posting updates to progress when possible

I'd be interested to know if you're going to follow the same level design logic as the original using one byte to define the screen layout for the entire game along with some logic that decodes it and allows consistent travel to and from each level including the underground shortcuts.

It was described in the post-mortem video by the creator David Crane and I found a nice write up here:
https://evoniuk.github.io/posts/pitfall.html

Thanks,

It was after reading that article that I decided to have a go

Yes I'm using the Random Generator from the Atari 2600 code to generate the screens and objects (not all sprite and objects data have been coded yet)
Underground shortcuts have been done.

Just fixed a masking issue when 3 logs are rolling - seems the mask backup data was going over a page boundary

[fizgog]

Added the swamp for the crocodiles.
Converted crocs to use sprite masking

[leenew]

This is coming along really well
I have never played the Atari original so could you tell me what features you still have to add?
Thanks,

Lee

[fizgog]

This is coming along really well
I have never played the Atari original so could you tell me what features you still have to add?
Thanks,

Lee

Still loads to do, following is not the full list

Collision detection
Animated vine
Tar pit
Animated quicksand
Treasures
Timer
Score
Lives
Sound

[lovebug]

amazing work, looking great and progressing swiftly

very well done

[fizgog]

amazing work, looking great and progressing swiftly

very well done

Thanks

Not sure about it progressing swiftly though, as I’ve not touched it in a couple of weeks as I’ve just not been able to find the time

[Rob_hawk]

Not sure about it progressing swiftly though, as I’ve not touched it in a couple of weeks as I’ve just not been able to find the time

It’ll be well worth the wait of that I’m sure

[oss003]

Hi fizgog, I was following this great thread and wondering if you made some progress on Pitfall?
Is it already playable?

Greetings
Kees

[fizgog]

Hi fizgog, I was following this great thread and wondering if you made some progress on Pitfall?
Is it already playable?

Greetings
Kees

I wish I could say yes, but work and home life has taken over pretty much of my free time at the moment. I've been working very long hours to complete a project for work 300,000+ lines of code and in-between this trying to renovate the house to keep the wife happy.

Hopefully I'll be able to get back to some quality 6502 coding soon.

NB I've currently got 2 projects in development this and Laser Zone

Regards
Shaun

[Rob_hawk]

Good luck with the work project Shaun and hope the renovation goes well.

Like all great things Pitfall will be worth the wait

Rob

[fizgog]

Finally finished major work project and have some time to myself

Started to add the swinging vine, video attached below

https://youtu.be/jMw6VysZe14


Anyone know what's the best way of hiding the vine going through the trees?

[FourthStone]

Finally finished major work project and have some time to myself

Started to add the swinging vine, video attached below

Anyone know what's the best way of hiding the vine going through the trees?

Looks great! Would a simple height check work for masking the vine at the foliage level?

[fizgog]

Finally finished major work project and have some time to myself

Started to add the swinging vine, video attached below

Anyone know what's the best way of hiding the vine going through the trees?

Looks great! Would a simple height check work for masking the vine at the foliage level?

Probably but I suppose I would need to code my own line drawing routine, currently for first test I’m just using the OS

See following thread for 6502 code
https://stardot.org.uk/forums/viewtopi ... 27#p376927

[TobyLobster]

Maybe something can be done by redefining the palette?

For example if logical colours 8 and 9 (flashing colours by default) are defined as black and green and these are used to draw the trees, then when the (say logical colour 7) rope is drawn on top then the trees become logical colours 8 EOR 7=15 and 9 EOR 7=14. So by also redefining colours 15 and 14 as black and green the change should become invisible.

[fizgog]

Maybe something can be done by redefining the palette?

For example if logical colours 8 and 9 (flashing colours by default) are defined as black and green and these are used to draw the trees, then when the (say logical colour 7) rope is drawn on top then the trees become logical colours 8 EOR 7=15 and 9 EOR 7=14. So by also redefining colours 15 and 14 as black and green the change should become invisible.

Thanks for that

I made a change late last night to handle the tree colour palette and also recoded the vine data to give it a longer swing from start of pond to end of pond to match the 2600 version, giving the below result

https://www.youtube.com/watch?v=mCcdFq1yAMQ