large number of sprites ie. Gauntlet

[zenassem]

First, sorry if I am asking too many questions for a noob, but many of you know so much about how to pull off many of the professional feats, that it's hard for me not to ask. I did try searching the forums, but some of your threads on this topic are a little more advanced than my level.

 

How did the game gauntlet appear to have so many sprites on the screen at one time?

 

I had made some guesse (don't laugh)

 

1) modified character sets (but the colors used and the size, collision etc... lead me to believe that it can't be this)

 

2)There are a few "actual sprites", and they are repeated displays of the actual sprites. (I can't imagine how or if this could be done)

 

3)Somehow, a few of the sprites are hardware sprites, and the rest are software sprites. (If that makes any sense)

 

well, it's kind of above my level right now. So I'm not expecting a code example or detailed explanation, but just a nudge toward the overall theory of how it was done would be great.

 

Thanks

~zen

[DanBoris]

How did the game gauntlet appear to have so many sprites on the screen at one time?

 

I had made some guesse (don't laugh)

 

1) modified character sets (but the colors used and the size, collision etc... lead me to believe that it can't be this)

 

2)There are a few "actual sprites", and they are repeated displays of the actual sprites. (I can't imagine how or if this could be done)

 

3)Somehow, a few of the sprites are hardware sprites, and the rest are software sprites. (If that makes any sense)

 

~zen

 

Probably not of the above! Looking at the technical specification of the Gauntlet hardware, it has very powerful sprite hardware. According to the specs it could display up to 56 motion objects (sprites) per scanline.

 

Dan

[kisrael]

Is it the Arcade version we're talking about?

 

My favorite "lots of enemies" game for 8-bit systems is Crossroads: I did a review of that game and its sequel at

http://www.classicgaming.com/rotw/crossroads/

 

It used character graphics, but any creature could be either fully "in" a character cell, or half in one, half out of one. Plus, the explosions (and warp-in effect) was a pixely particle effect, maybe sprites, I'm not sure.

 

Brilliant game though, can't believe it was just a magazine type-in.

[zenassem]

Ooops, I failed to clarify that I was referring to the 8-bit ports. Specifically the Atari 400/800/xl/xe version from Mindscape.

 

I'll try my best to remember the next time I post in the programming forum.

 

BTW, I'm using Gauntlet as a mere example. Most of my programming from way back was strictly in basic. And I took the Atari Basic Guide as the Gospel back then. "4 players , 4 Missiles".

 

Then one day I picked saw an article inCompute! that showed how the 4 Missiles could be combined to make a 5th Player.

 

Great! But, I never could understand how some commercial games had numerous objects moving all around.

 

First, I guessed that there was some "magic" chip inside the cartridge. But that didn't make sense, because I had plenty of games on Floppy that had all of these "players" and "missiles" buzzing all over.

 

Gauntlet is a good example of this (although the atari port really wasn't good after seeing it on the C6?). So there is obviously a way to have more sprites displayed on the screen then my basic books ever lead me to believe (kinda the same sucker punch as when I found out about antic modes vs Basic modes).

 

Now here is what really adds to my confusion....

 

One day I was playing Ghostbusters on my friends C64. And I noticed that the graphics were not only sharper, but the men had more colors and a better color scheme. I couldn't understand why the Atari version had the men wearing blue shirts. So one day I read an article about multicolor sprites (in basic). The method was to over lap two players.

 

So I made the following assumption:

That's what must be going on in GB's. Each guy is 2 players and where the players cross is where the third color comes from. The ghost must then be made up of the 4 missiles. Hence the single color. The traps were character sets. etc.. etc... and so was the lasso like object that springs up from the trap. The lasers are just drawn lines. So, I was all happy and fuzzy thinking that I figured it out.

 

But with that line of thinking... how could I explain Gauntlet? Well, I couldn't. And I still don't understand how it's done on an Atari 8-bit.

 

At least space invaders I could reason that each alien is actually a remapped character set. But looking at the graphics in Gauntlet, this method wouldn't work.

 

So I am stumped, and I have been stumped from nearly 15 or so years ago.

[kisrael]

It's a very worthwhile question for the aspiring programmer or even the casual fan...do you have a ROM or better yet (for the casual person again) some screenshots for us to look at?

[DanBoris]

First a question, was there an Atari 8-bit version of Gauntlet? I did a web search and the only thing I could come up with from Mindscape was an Atari-ST version along with a few other platforms, but not the 8-Bit Atari.

 

As for how to get multiple moving objects on the screen at the same time, there are a few techniques, each with it's own pros and cons.

 

1. Sprite re-use. Since 8-bit sprites are the full hight of the screen it's an easy matter to change the horizontal position of the sprite between scan lines which would allow you to use the same sprite multiple times on the screen. Still can't do more the 4 sprites on a line.

 

2. Sprite multiplexing. Instead of displaying all the sprites at the same time, display 4 during one video frame, then another 4 during the next. Leads to some flicker but gives you 8 sprites on a line. This can also be combined with technique 1.

 

3. Draw the sprites in bit-mapped mode. This gives you an unlimited number of 4-color sprites but is very processor intensive. Atari 5200 Galaxian uses this teqnique for the enemies in formation. The movement of the formation is done with using fine scrolling so the enemies don't have to be re-draw until they break formation at which point I think they become player sprites.

 

4. Character mode graphics. This is similar to 3 but doesn't take up as much processing power. The downside is that it's hard to get total freedom of movement and sprites cannot overlap each other.

 

Also, multi-colored sprites can be achieved without having to use multiple sprites. If you don't need multiple colors on the same line of a sprite, you can change the sprite color on different scanlines so the same sprite shows up in multiple colors.

 

Dan

[kisrael]

4. Character mode graphics. This is similar to 3 but doesn't take up as much processing power. The downside is that it's hard to get total freedom of movement and sprites cannot overlap each other.  

So these can be multicolor and all, right? It's basically using tiles for everything. Given how it looks like even the Arcade Gauntlet restricts its world, this might be the best solution...use characters for all monsters (make sure you have a different set of graphics for every floor type the monster can walk on...), maybe use characters or sprites for the players, use sprites for the projectiles...

 

Hmm, or maybe not. ..the arcade looks like it goes in half-character steps? Would that mess up things, you'd have to have extra graphics for every monster next to monster combination?

[TMR]

First a question, was there an Atari 8-bit version of Gauntlet? I did a web search and the only thing I could come up with from Mindscape was an Atari-ST version along with a few other platforms, but not the 8-Bit Atari.

 

There's an A8 version yes, looks like it's been roughly ported from the C64 version at a guess.

 

4. Character mode graphics. This is similar to 3 but doesn't take up as much processing power. The downside is that it's hard to get total freedom of movement and sprites cannot overlap each other.

 

Done like that yes, look at the way the ghosts move and they step a character cell at a time (Gauntlet is designed so that they needn't overlap each other). The players are made with... (wait for it...) players! =-)

[TMR]

Oh, as a general aside it's good to remember that players can be recycled down the screen - if you see lots of objects moving, watch which cross over on the same rasterline and which don't to get a few hints about what's happening. =-)

[zenassem]

Wow! All of you have contributed a wealth of knowledge, and it gives me a lot to experiment with this weekend. I'll post a screenshot of the A8 version when I get home (about an hour from now). Be prepared!!! It's quite ugly. But, that's why I am choosing to work on this. I really think that with some hard work and the help from this site, I could produce a better looking port with smoother gameplay.

 

The A8 version is really bug-ridden and not all that fun to play. It suffers from slowdown, flickering, poor control/firing, even in single player mode. The orignal I had owned was a C64 B-side. "I fell for the old - put a different computer's screenshot on the box trick!!!" Needless to say I was very dissapointed. It has annoyed me to this day, the difference of quality between the C64 port, and the half-baked atari masacre!!!!

 

Thanks for sharing your thoughts. I will attempt some mock-ups and demos this weekend.

 

~zen

[Schmutzpuppe]

3. Draw the sprites in bit-mapped mode. This gives you an unlimited number of 4-color sprites but is very processor intensive.

I took a short look at it, gauntlet use the bitmap way.

[Schmutzpuppe]

btw. I guess I would have used charmode for gaunlet.

The fact that you don't have to care about overlapping makes it imho comparative easy.

I think the C64 gauntlet use chars the it's a lot faster than the a8 version.

Maybe TMR can give us more detailed information about it.

Gauntlet could be much sweeter on the a8 compared to the existing version.

[Schmutzpuppe]

Ok the c64 version use chars.

I don't know much about the c64 but the studioX64 sprite/font ripper is a beautiful tool

[zenassem]

Schmutzpuppe,

 

Thanks for taking the time to research that. I will try a couple of methods and come back here with my results.

 

Here are the screenies:

 

Arcade

 

Commodore

 

*******************

Atari 400/800/xl/xe

 

Perhaps someone with some experience can pick apart the display that the A8 version implemented. I can already see - as was stated - that unlike the arcade version which has the ghost overlapping; the A8 the enemies do not overlap. They are confined to a tilebased grid.

 

 

Well at least our port looks better than the apple ii, and iie below. That was Atari's aimed competition.

 

apple ii

 

apple iie

 

Ughhhh!!!

 

(Something else of interest as I was researching. The actual coin-op used the 6502 as the sound CPU.)

[zenassem]

Here on this site are images of the 7800 game Dark Chambers, that inspired Gauntlet. The 7800 version looks cool, although I have never played it. Also here is the 2600 cart Gauntlet which has nothing in common with the game I am referring to.

 

It would be fun if one of the 2600 gurus could work up something. It could use some of the same techniques that were use in Adventure. Which of course got me hooked forever on Maze type games.

 

For those who love the AtariST here is a screenie of probably the best port I have seen. In fact it looks 3X's as good as the DOS version.

 

The Beloved an Envied (at least by me) AtariST port:

 

~zen

[TMR]

I think the C64 gauntlet use chars the it's a lot faster than the a8 version.

Maybe TMR can give us more detailed information about it.

 

To be honest, i thought the two versions were working the same way - just with more donkey work for the C64! It appears to just have a block of memory put aside for the map and the nasties are written into that area - they move around at one character steps (4 pixels horizontally and eight vertically) whenever there's time to shift them. Then a window is written into the play area once a frame and four hardware sprites added for the two players and their bullets and the other four sprites are masking the horizontal edges of the scrolling area to get it down to 32 characters across.

 

The theory's perfectly sound for the A8, as i said i was assuming the same thing was being done but the progammer hadn't been up to the job...!

[zenassem]

@TMR,

Thanks for the info. It amazes me when you guys can see those hidden details & tricks from one still screenshot. I would never have thought that players would be used along the horizontal edges.

 

I'm ot exactly sure I get what effect that has. Are you saying that the player are the height of display - therby boxing in the scrolling map? What would happen to the display if they weren there?

 

 

**********

I realize the C64 screen didn't paste so good. So here is another one so that you can see the difference. I also have the title screen for both the c64 and atari

 

c64 in-game screen

 

 

Please look at the two title screens.

 

Would I be wrong in feeling that the programmers just got lazy with the Atari8 screen? I know that it's easier to work with color in the c64 bitmap modes, but surely the Atari can display something just as good.

 

c64 TITLE Screen

 

VERSUS

 

A8 TITLE Screen

 

 

Please share your comments. And feel free to let me no if I am wrong in being harsh on the programmers.

 

 

~zen

[zenassem]

(I really need the edit feature to return)

Just a quick note: The "GAUNTLET" logo in the above screens, changes colors rapidly to give a glowing-chrome like effect. The C64 screen wasn't grabbed at the best possible part of the cycle. Hence the reason, it looks weird.

[Shawn Jefferson]

In Atari800Win PLus, you can press F8 to enter the debugger and then type "dlist" to get a listing of the display list. This will let you know what graphics mode the game uses for the screen, which can tell you if a game uses a bitmapped mode or a character based mode.

 

There are other things you can do as well, like turning off the players, missiles, resetting the character base address, etc... to see how other effects were done.... Heaven has posted some information on that in various threads IIRC.

[Heaven/TQA]

did the atari programmers of gauntlet ever noticed in bitmap mode you could use the 5th colour... i think it was a quick port imho...

 

i even think that the colours are badly choosen... and the player overlays over the score board... aaaarg...

 

so i guess the job was not make a perfect gauntlet conversion but port the c64 version instead to other systems... (or better... use the spectrum version... ) so that's why the apple versions look so similar...

 

hey... but it could even be worth... the programmer knows how to softscroll...

 

imho good example of softsprites

 

- dropzone

- international karate (ok... not the same kind of engine)

- zone ranger (ok... bitmap mode...)

- many early synapse games like shamus etc...

- berzerk

... and many more i cant recall at the moment...

 

TMR... it'seems we have to setup a new sprite engine competition...

[TMR]

@TMR,  

I'm ot exactly sure I get what effect that has. Are you saying that the player are the height of display - therby boxing in the scrolling map? What would happen to the display if they weren there?

 

Well, i was talking about the C64 version at that point; since the doesn't have any way to reorganise it's screen, it's always 40 by 25 characters. Masking vertically is "just" a matter of using a feature of $d011 (enabling bitmap and extended colour mode at the same time, it goes black) but the horizontal smooth scroll masks can only pull in a character each side of the screen. To get a 32 character wide play area like Gauntlet uses requires at least one sprite a side to mask off the rough edges of the scrolling.

 

Would I be wrong in feeling that the programmers just got lazy with the Atari8 screen? I know that it's easier to work with color in the c64 bitmap modes, but surely the Atari can display something just as good.

 

The C64 is using seven of it's hardware sprites with at least horizontal expansion set to display the logo and then altering the sprite colours every few rasterlines. It would be possible, in theory at least, to build a better screen and still leave a colour free to be split on the A8 like that but techniques like G2F are younger than the game.

[TMR]

imho good example of softsprites

 

- dropzone

- international karate (ok... not the same kind of engine)

- zone ranger (ok... bitmap mode...)

- many early synapse games like shamus etc...

- berzerk

... and many more i cant recall at the moment...

 

TMR... it'seems we have to setup a new sprite engine competition...

 

Difficult one, what sort of "rules" are we talking here? Each of those examples has a "drawback" somewhere along the line, IK has to deal with only two sprites at the same time, Dropzone has objects obscuring each other if they pass over the same space and i suspect some code to try preventing that as much as possible, Zone Ranger loses some speed to the sprite handling...

 

Gauntlet should've had a good system, if it were handled using the character-based screen like the C64 version it could have been very fast since the C64 has to map dump to the screen and the Atari doesn't.

[zenassem]

I'm going to try using modified character sets for most of the in-game graphics. While I try to do most of my work on the actual Atari 65/XE I figure for this type of project I will need to make as much use of the PC tools as possible to speed up my progress.

 

I just downloaded envisionPC to modify the character sets easier. I haven't used it so, I have some reading to do. I have the atari800win plus, the Gauntlet.ATR, the atari810 diskdrive emulator and the sio2pc cable.

 

If anyone knows of other tools I should consider please post. I figure I'll code it in mac65. I am not trying to do an exact duplication of the current Mindscape A8 version of Gauntlet ; But rather, a complete re-"PORT" of the original Arcade. If anyone has ideas of screen setup/modes please share.

 

Thanks

~zen

[Wrathchild]

Software sprite routines that I'd like to understand one day

would be the Zeppelin Games' Draconus, and also the

games 'Basil - Mouse Detective' and 'Black Lamp' appear

to have good routines too.

[zenassem]

@Wrathchild, I will have to look at them, my memory is a bit fuzzy when it comes to the games on the A8. Adding to the confusion, was all the hacked software copies that I had back then. A lot of them changed the name of the game or other text elements. (Did anyone else have the copy of Karateka? I really thought I was out to save the "nymphet"!

 

 

*************************************************************

(Some inital thoughts as I experiment....)

 

I have been playing around with EnvisionPC font editor, and think I'm starting to see what the A8 programmers were facing.

 

 

If it's true that they used character sets for the much of the Gauntlet graphics...

 

 

It's not as easy as I thought it would be to design the ghosts. When using Antic mode # 4 for instance. The colors I get depend on how I use the 8x8 grid. So while, I have 5 colors, It's quite difficult to get the exact results I am looking for. The funny part is, one of my first attempts came out looking "Exactly like the current A8 version".

 

I'll tinker with it a little bit more. But, there are still alot of other areas where the game can be improved. Mainly gameplay, speed, AI, difficulty balance and the screen layout.

 

------------------------------------------------------------------------------------

 

Can someone tell me if they believe that the character set in the A8 version was dispalyed in Antic mode #4?

 

If you were me, which Antic mode # would you use for a game like this?

 

 

Thanks,

~Zen