IntyBasic: Multiples of Sprites?

[Cybearg]

On the Atari 2600, there are TIA registers that can be set to cause multiple instances of a single sprite to display in a horizontal row, like so:

x1:

 

x2:

 

x3:

 

This still only counts as one sprite because the kernel is just drawing the sprite three times in a row.

 

Is there any equivalent of this for the Intellivision, or could it be added in somehow? This little trick can be enormously useful for making one sprite seem like a lot more, and while it's great that there are 8 sprites for the Inty, I have a few use cases that would supremely benefit from this functionality.

 

Can it be done?

[intvnut]

There's a technical limitation on the Intellivision that prevents this. The STIC registers that control sprite positions are not accessible during active display. There's a small few-thousand cycle window when they're visible during vertical retrace, and then after that the CPU is blocked from access.

 

This isn't an IntyBASIC limitation, but rather an Intellivision limitation.

[intvnut]

There's a technical limitation on the Intellivision that prevents this. The STIC registers that control sprite positions are not accessible during active display. There's a small few-thousand cycle window when they're visible during vertical retrace, and then after that the CPU is blocked from access.

 

This isn't an IntyBASIC limitation, but rather an Intellivision limitation.

 

Actually, I think I was thinking of the TIA trick of repositioning a sprite after it had displayed to get multiple copies vertically.

 

Still, it's an Intellivision limitation that each MOB appears in only one location on the screen in a given frame.

[Cybearg]

Noted, thanks. I'll just have to design around that limitation, then.

[intvnut]

Now that said, you can sometimes use background cards in place of MOBs / sprites, if you get creative updating the information in GRAM. I don't know if IntyBASIC offers any hooks for this, but it might be something interesting to add in the future.

 

Space Patrol uses this heavily, along with a little bit of MOB multiplexing to get a large number of moving objects on-screen at once. For example, the forward-shooting bullet on the tank is actually a background card, not a MOB. Likewise for the rocks and craters.

 

I don't know what you have specifically in mind for your game, but hopefully it goes well and you'll tell us all about it down the road. :-)