15 replies to this topic

[Lost Monkey]

I am studying Atari 2600 games with assymetrical playfields and multiple sprites for a project I am working on. I am not interested in moving playfields - they should be static, and involve full interaction with the sprites... IE playfield appears within the same scanlines as the sprites.

If you can think of any titles I should check out, please list them here.

A good example of what I am looking for would be would be Yars' Revenge.

Thanks!

[Cupcakus]

Quest uses an Asymetrical/Reflected playfield.

And believe it or not, Kablamo! does too for the little white boxes in the center of the screen. It doesn't have to... but it was more fun to include it.

[Lost Monkey]

This is the type of thing I am looking for:

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[davidbrit2]

I think Donkey Kong and Donkey Kong Jr. would make excellent examples. Kangaroo fits in this category as well. And off the top of my head, I think Congo Bongo qualifies, too, doesn't it?

[Nathan Strum]

How about the "reactor" planet in Gravitar?

[Osmeroid]

Xenophobe & the 'upper' screen in Pressure Cooker?

[Godzilla]

check out congo bongo and others in the thread on 2600 arcade ports. lots of assymetrical playfields there.

[EricBall]

Skeleton uses a reflected asymetrical playfield to draw the maze and both player sprites for the Skeleton.

Ms Pac Man uses an asymetrical playfield for rows with dots, and a reflected symetrical playfield for the rest of the maze.

It is very, very difficult to combine an asymetrical playfield with sprite reuse since a normal repositioning routine requires an entire scanline for itself.

[Paul Slocum]

I disassembled some of Maze Craze to learn some tricks to do Marble Craze. Maze Craze has an asymetric playfield and displays both players, both missiles, and the ball. I only did a little bit of the kernal and it's not commented very well, but e-mail me if you want to look at it. The Thrust source would probably be helpful too.

-Paul

[Andrew Davie]

EricBall said:

Skeleton uses a reflected asymetrical playfield to draw the maze and both player sprites for the Skeleton.

Ms Pac Man uses an asymetrical playfield for rows with dots, and a reflected symetrical playfield for the rest of the maze.

It is very, very difficult to combine an asymetrical playfield with sprite reuse since a normal repositioning routine requires an entire scanline for itself.

Ah, it just 'clicked'. This is probably why Ebivisions PacMan has horizontal black lines in the playfield regularly spaced down the screen. It's where their sprite management routines are repositioning sprites for re-use.

Cheers
A

[ZylonBane]

Long story short-- You can't freely position a sprite on the same line as an asymmetric playfield. Both operations demand the CPU's undivided attention.

If you want to do a KC Munchkin port (major cool points), you're going to have to either use a symmetric maze, or leave blank lines where the sprite positioning is done.

Third, tricky option might be to leave the horizontal maze spans symmetric, but the vertical spans asymmetric.

adavie said:

Ah, it just 'clicked'.  This is probably why Ebivisions PacMan has horizontal black lines in the playfield regularly spaced down the screen.  It's where their sprite management routines are repositioning sprites for re-use.

No, that would only cause the standard "comb" down the left edge. The reason the stripes go all the way across the screen is because the white dots are on those lines.

Paul Slocum said:

Maze Craze has an asymetric playfield and displays both players, both missiles, and the ball.

No trick here. None of those objects are multiplexed, so the kernel just positions them before it starts drawing the playfield.

[Lost Monkey]

Thanks for the responses guys.. I have been too busy to even look at the code for the last week or so, but I hope to get back into it tomorrow.

@Clay: How much digging have you been doing in the Ms Pac Man code? You mentioned it on the Stella list, and I was thinking of giving it a going over tonight before getting some sleep...

In the end, I would rather offer a port with a bunch of different symmetrical mazes, than assymetrical mazes with only the "Teddy Bear" difficulty level..

[Paul Slocum]

adavie said:

Ah, it just 'clicked'.  This is probably why Ebivisions PacMan has horizontal black lines in the playfield regularly spaced down the screen.  It's where their sprite management routines are repositioning sprites for re-use.

Other way around. The lines that don't have dots are symetrical and make it easier to reposition since the playfield doesn't have to constantly be updated across the line.

ZylonBane said:

Paul Slocum said:

Maze Craze has an asymetric playfield and displays both players, both missiles, and the ball.

No trick here. None of those objects are multiplexed, so the kernel just positions them before it starts drawing the playfield.

Plenty of tricks in there to save cycles. It's not easy to display all that and an asymetric playfield along with other stuff too. Especially since the maze is not stored as a straight bitmap (if you look at a screenshot you can see there wouldn't be enough RAM.) These saved cycles can be used for other things like helping position a sprite, or in the case of Marble Craze, reading the paddles and allowing independent playfield coloring on the left and right sides of the screen.

-Paul

[ZylonBane]

Paul Slocum said:

Plenty of tricks in there to save cycles.

I didn't mean that there were no tricks in the entire game. Heck, the entire 2600 architecture is one big trick. I just meant that there's no trick to positioning sprites over an asymmetrical playfield as long as you don't do any multiplexing.

[EricBall]

Paul Slocum said:

Plenty of tricks in there to save cycles.  It's not easy to display all that and an asymetric playfield along with other stuff too.  Especially since the maze is not stored as a straight bitmap (if you look at a screenshot you can see there wouldn't be enough RAM.)  These saved cycles can be used for other things like helping position a sprite, or in the case of Marble Craze, reading the paddles and allowing independent playfield coloring on the left and right sides of the screen.

So true! For Skeleton, each line I had to check to see if the Skeleton is on that line, and load the player registers if so, and check to see if the radar is on that line, and enable/disable the ball register. Lots of very careful cycle counting.

[raindog]

adavie said:

Ah, it just 'clicked'.  This is probably why Ebivisions PacMan has horizontal black lines in the playfield regularly spaced down the screen.  It's where their sprite management routines are repositioning sprites for re-use.

No, those black lines in the playfield are there because they also draw the dots using the playfield but they wanted them to be white. So I guess they had the choice between black lines in the playfield or white lines in the playfield

Rob