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Crystal Castles for Atari 5200


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Anyone know how the 5200 trackball sends its input?

 

From another thread, I don't know how accurate this statement is:

 

The 5200 trakball is the tool of the devil.  

 

It's just a crufty design. In order to make the trakball "compatible" with joystick games (and thus to avoid any software changes for already released games) the trakball functions like a "virtual" joystick. As you spin the ball, a current (somewhat, sorta, roughly, almost) like the one controlled by the potentiometer in the 5200 controller is fed to the 5200. The faster you spin the ball, the farther the "joystick" tilts.  

 

On a "real" trakball (like a Missile Command or Centipede arcade game) the trakball outputs digital pulses in quadrature-- the game board sees a distinct number of "steps" in a certain direction as a result of the ball spinning. Nice and crisp, smooth input...  

 

The 5200 trakball's output is a spastic approximation of an auto-centering joystick being "slapped" as the game is played. It's "trakball-like", but nothing like the fine control you might otherwise expect.  

 

-Clay

 

However, if this is 100% true then every 5200 game should theoretically work with a trackball, which is definitely not the case.

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Anyone know how the 5200 trackball sends its input?

 

Some explanation and how it relates to CC here I think...

 

http://www.atariage.com/forums/viewtopic.p...er=asc&start=27

 

I fought with the 5200 Trakball for a LONG time trying to get something "good enough" for Crystal Castles.

 

The problem is that the 5200 TB emulates a joystick.  When it's at rest the stick is 'centered'.  When you spin to the right, the virtual joystick 'tilts' to the right.  If you spin faster the 'joystick' moves farther.

 

On a real arcade game, a trakball is an encoder-- it tells you the direction and the number of pulses moved.  It's just like a mouse on a PC. (Except it's upside down.)

 

The problem gets to be with how the Crystal Castles code works and how the trakball is read.   CC, being for the Atari 8-bits, was designed for digital joystick inputs.  The method that Bentley moves is rather intimately tied to the games main timing loop.  There are lots of checks performed with Bentley's position as the game 'updates' his position based on input.  (On a gem?  On an enemy?  On the path?  On an elevator? etc...)

 

Since the code is always expecting Bentley to move only one 'delta' at a time this works dandy.  If however you try to move Bentley *more* than one unit at a time (like if you're trying to approximate a fast trak-ball spin) the collision detectors can break-- you'll pass over gems, through enemies, etc.  To make matters worse, animation frames are triggered by seeing sequential position values, skipping over any makes Bentley skip animation frames.  

 

One thing that *does* work is to slow down the movement summing.  Right now I have two speeds for Bentley depending on how far you move the joystick.   If you need to do something tricky you can tilt the joystick less than half way and he'll walk along slowly.  If you tilt the joystick farther he moves at regular (full) speed.

 

This same technique with the trakball however, sucks.  The 5200 trakball is really low resolution.  You can give the trakball a mighty spin and the "joystick" will seem to move pretty far-- for a fraction of a second.  What it boils down to is that for 'small' movements the trakball circuitry is really spastic (twitchy outputs), so you can only rely on larger values to get out of the noise.  However, in order to get at the larger values the player has to spin that trakball a LOT.  It's just not much fun to play that way.

 

(In all fairness, I also think that the trakball motion in Missile Command and Centipede is totally horrible.  But again I'm an arcade guy primarily so I might just be being snooty.) ;-)

 

So, in the 5200 Crystal Castles I *could* leave the trakball support in, but I think it's pretty pitiful.  I'd almost rather take the flak for "why isn't there trakball support?" than "why does trakball support suck?".  :|  

 

-Clay

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Hey you guys, if the game could be made to work with either a Trak-ball or digital stick (my only 5200 controllers), I'd jump at buying a cartridge of this like a shot, even though I've never seen a screen shot. I just got 2600 Crystal Castles last week as part of an eBay lot too :wink:

 

Any chance of making this as a sort of reproduction cartridge? I don't own a computer so ROM downloads just don't do it for me! (Before you all ask, I'm using a 7-1/2+ year-old WebTV. I like my old technology!)

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