Help Hacking Playfields

[SalemFrost7800]

Can anyone explain what all is involved in hacking playfields? How do you locate the playfield in the disassembly or on hack-o-matic 2 and make changes?

 

Thanks, Tim

Edited July 18, 2006 by usinoh

[SeaGtGruff]

Can anyone explain what all is involved in hacking playfields? How do you locate the playfield in the disassembly or on hack-o-matic 2 and make changes?

 

Thanks, Tim

 

If you have a disassembly, look for a store command-- STA, STX, or STY-- with a playfield register-- PF0, PF1, or PF2. For example: "STA PF0" or something similar. Then you can backtrack to see what's being loaded into A, X, or Y-- or more importantly, *where* the data is being loaded from. Hack-O-Matic 2 might help you *change* the playfield data table once you locate where it is in the ROM, but it won't be as easy to find the data with Hack-O-Matic 2 as if you are using a disassembly.

 

Michael Rideout

[Pac Munchkin]

Can anyone explain what all is involved in hacking playfields? How do you locate the playfield in the disassembly or on hack-o-matic 2 and make changes?

 

Thanks, Tim

 

I found that there are really two playfields. The apperance one we see and the math one the computer sees. I tried changing the maze in Alien it only changed the apearance all sprites still followed the old maze like nothing was changed at all. So I think this requires some assembly programing to actually make play feilds that are changed in looks as well as function.

 

Wade

[SalemFrost7800]

Can anyone explain what all is involved in hacking playfields? How do you locate the playfield in the disassembly or on hack-o-matic 2 and make changes?

 

Thanks, Tim

 

I found that there are really two playfields. The apperance one we see and the math one the computer sees. I tried changing the maze in Alien it only changed the apearance all sprites still followed the old maze like nothing was changed at all. So I think this requires some assembly programing to actually make play feilds that are changed in looks as well as function.

 

Wade

 

At this point I am only interested in cosmetic changes for a few game ideas I have

[Pac Munchkin]

Can anyone explain what all is involved in hacking play fields? How do you locate the play field in the disassembly or on hack-o-matic 2 and make changes?

 

Thanks, Tim

 

I found that there are really two play fields. The appearance one we see and the math one the computer sees. I tried changing the maze in Alien it only changed the appearance all sprites still followed the old maze like nothing was changed at all. So I think this requires some assembly programming to actually make play fields that are changed in looks as well as function.

 

Wade

 

At this point I am only interested in cosmetic changes for a few game ideas I have

 

 

Oh that is easy cosmetic changes, like I made the Alien Maze look more like Pac Man maze. Here is what I do with Bit Hacker. I find what looks like the play field then I make a small change maybe add or delete 4 bits and I save it and play it to see what I changed where it appears, a lot of times everything is upside down so switch views from ascending to descending in the bit hacker. this way it will be right side up, easier to find.

Another thing is since it is only 8 bits across you are going to see all of the screen in that little 8 bit wide line so you might see first the right side then middle then left or Bottom Middle and Top this is very confusing but you can find everything if you take it slow and keep testing. if you mess something up change it back if you lose it then you need to do showgfx for the hack version you messed up and the original, and get a text file compare program to compare the two files and find where you messed up to change it back. I got mine free at down load.com

 

Hope this helps!

Wade

[Nukey Shay]

Can anyone explain what all is involved in hacking playfields? How do you locate the playfield in the disassembly or on hack-o-matic 2 and make changes?

 

Thanks, Tim

 

I found that there are really two playfields. The apperance one we see and the math one the computer sees. I tried changing the maze in Alien it only changed the apearance all sprites still followed the old maze like nothing was changed at all. So I think this requires some assembly programing to actually make play feilds that are changed in looks as well as function.

 

Wade

 

Yup...games rarely use the actual playfield data to establish sprite movement boundries (and due to the 2600 playfield's exotic nature, this is probably reduced to "never"). The biggest problem with the 2600 is that the playfield that is constructed is unusable to later parts of the program...there is no screen ram holding all of the data unlike other consoles/computers.

[Pac Munchkin]

Ah I actually understand this, thanks Nukey, you are a great guy helping us beginners so many times stuff flies over my head but I keep on trying. us beginners must give you a headache at times! lol

 

Thanks again.

Wade