Alien Wave Patterns

[fizgog]

Currently disassembling a C64 game, but if I fail does anyone know of any good tutorials on making alien attack patterns?

Or even an online program to generate the attack pattern data by using the mouse to draw the pattern, maybe there has been one done in Basic for the Beeb?

[Rob_hawk]

A little bump for this as I was interested to hear if there were any options.

[Phantasm]

I made a program for doing this back in the day for some of my friends who were working on an Amiga game.

You could drop way-points on the screen using the mouse and position them as needed and then you could generate a curve matching the points and save the resulting dataset which was a list of x,y coordinates for the curve. You could also preview the results in the application.

sorry not much help to you, but a nice trip down memory lane for me

[Rob_hawk]

sorry not much help to you, but a nice trip down memory lane for me

That’s great to hear that you created this for an Amiga game. Minus the mouse I wonder if anyone ever came up with similar in BBC Basic?

[fizgog]

In the end I did manage to extract the alien attack patterns for LaserZone.

Good idea with using a mouse to draw the curves and then converting them to data points, could be easily done on a PC and then converted to EQUB data for the beeb.

I just wondered how they did it back then - graph paper possibly?

Two games that spring to mind are Zalaga and Galaforce

[tricky]

For the UFOs in scramble, I played the game in MAME while recording it then wrote a program to track the land moving and the saucers to output the path. I had to track the land as well as it didn't scroll two pixels every frame, but sometimes did 1 or 3!

[fizgog]

For the UFOs in scramble, I played the game in MAME while recording it then wrote a program to track the land moving and the saucers to output the path. I had to track the land as well as it didn't scroll two pixels every frame, but sometimes did 1 or 3!

Thanks for the explanation tricky

[Rob_hawk]

Hi Shaun,

As a by product of investigating something else today I came across an article about a current day arcade conversion of Galaxian to the C64. It was Z80 to 6502 and the topic of Alien wave patterns came up to keep the 6502 version as close to the arcade as possible. I thought you might find it interesting or useful or both!

Here’s the game and dev blog:

https://arlagames.itch.io/galaxian-dx-c64

Here’s the commented Z80 arcade disassembly:

http://seanriddle.com/galaxian.asm

Cheers

Rob

[fizgog]

Thanks Rob, I'll have a look tonight

[Rob_hawk]

Thanks Rob, I'll have a look tonight

Pleasure Shaun. Let me know if you find any of it useful.

[Kecske Bak]

Roland Waddilove covered this exact topic in The Micro User, in his series about Writing 6502 Machine Code Games (this series was a sequel to Kevin Edward's original series). At the weekend I'll be able to find which issue this was in and send you a link.

[Rob_hawk]

Roland Waddilove covered this exact topic in The Micro User, in his series about Writing 6502 Machine Code Games (this series was a sequel to Kevin Edward's original series). At the weekend I'll be able to find which issue this was in and send you a link.

It was January 87 edition I believe and I've attached the series as a PDF for those interested. It's future work for me

RolandWaddilove6502TheMicroUser copy.pdf

(9.04 MiB) Downloaded 20 times

[fizgog]

Thanks for that I've just read part 4 "On the track of sprites", although the article was interesting it doesn't actually explain how the pattern data was generated in the first place

I'm beginning to think all they did back in the day was to sit down with some graph paper and draw some patterns and then convert by hand to data statements.

[Rob_hawk]

Glad it was a good read. I think you could be right with the pen and paper approach

Have a great weekend Shaun.

Rob

[fizgog]

When I was a kid I thought the developers BITD were Gods with magical powers creating amazing games, the more and more I learn and code my own games, it's seems no longer the case which is sad.

[Rob_hawk]

I think they are still gods as they gave and continue to give great pleasure even decades after they were originally conceived. To me when I look at your games you’re in the same category. The old BBC games and the ones you write plus people like Chris , Lovebug and Tricky (plus many others) are one of the reasons I decided I wanted to learn to code. It’s something I have never done professionally so it does not come too easily for me! I always wanted to understand how it was done…

Your game creation skills are at a great level so now you just understand more the secrets Often the way with things in life, you lift the covers and things are rarely as you perceived them to be!

[fizgog]

Behind the curtain

[Rob_hawk]

Love it

[tricky]

There was a lot of graph paper, hex and if you were lucky printouts bitd
Somewhere I have pushed off fonts, sprites and a couple of landscapes including the one in Jeltron, although Gil did the hex conversion of that.

Iirc, Astro Blaster has do move M N times then the next, at the end jump back to P, this allows the ships to drop in quickly the repeat a pattern that usually levers them a bit lower after doing it than before. The patterns were ripped from the ROMs!

I usually tried to make the movement in my games procedural, whether that was head for the player or move in a dir until something happens then pick a new dir.

[fizgog]

For the IDS movement in LaserZone I ended up doing this simple procedure as I couldn't figure out how it was done in the original.

1. Set random x,y position on screen
2. Set decay factor
3. Set random direction and length of movement
4. Move for the length of direction
5. Decrement decay
6. Loop back to number 3
7. Destroy IDS