Horizontal scrolling techie question

[mikeb]

Hi Chaps,

 

Can anyone elighten me, an ex-2600 programmer has told me that completely smooth horizontal scrolling was very difficult to achieve on the system, and that for an early game of theirs they didnt want to use horizontal as opposed to vertical scrolling as horizontally it would have had to have scrolled in either 4 or 8 pixel 'chunks', but they can't remember which. Anyone know which of those numbers is correct?

Edited September 7, 2010 by mikeb

[e1will]

Hi Chaps,

 

Can anyone elighten me, an ex-2600 programmer has told me that completely smooth horizontal scrolling was very difficult to achieve on the system, and that for an early game of theirs they didnt want to use horizontal as opposed to vertical scrolling as horizontally it would have had to have scrolled in either 4 or 8 pixel 'chunks', but they can't remember which. Anyone know which of those numbers is correct?

 

Yes, 4 pixels is correct, if you're using the playfield (which most games do.)

 

--Will

[mikeb]

Hi Chaps,

 

Can anyone elighten me, an ex-2600 programmer has told me that completely smooth horizontal scrolling was very difficult to achieve on the system, and that for an early game of theirs they didnt want to use horizontal as opposed to vertical scrolling as horizontally it would have had to have scrolled in either 4 or 8 pixel 'chunks', but they can't remember which. Anyone know which of those numbers is correct?

 

Yes, 4 pixels is correct, if you're using the playfield (which most games do.)

 

--Will

 

Great, thanks Will.

[Thomas Jentzsch]

Yes, 4 pixels is correct, if you're using the playfield (which most games do.)

 

Great, thanks Will.

You can overcome this limitation by what I call "delayed scrolling".

 

Instead of slowly scrolling one PF pixel every few frames (e.g. like Vanguard, which doesn't look smooth), you wait until you have to scroll a few PF pixels and scroll them all at once, moving 1 PF pixel every 2 or 3 frames. I did that in Thrust (and the unreleased Boulder Dash homebrew) and it looks very smooth.

[SeaGtGruff]

Yes, 4 pixels is correct, if you're using the playfield (which most games do.)

 

Great, thanks Will.

You can overcome this limitation by what I call "delayed scrolling".

 

Instead of slowly scrolling one PF pixel every few frames (e.g. like Vanguard, which doesn't look smooth), you wait until you have to scroll a few PF pixels and scroll them all at once, moving 1 PF pixel every 2 or 3 frames. I did that in Thrust (and the unreleased Boulder Dash homebrew) and it looks very smooth.

Do you mean a "jerky" scroll-- i.e., scroll a few PF pixels quickly, then stop scrolling and wait until it's time to scroll a few more PF pixels at once? Scroll, stop, scroll, stop, scroll, etc.? I can see where that would look better (as long as the pauses could be worked into the game), because coarse PF scrolling looks better when it's fast (60 Hz, or 50 Hz for PAL) rather than 1 PF pixel every few frames.

 

Also, I think horizontal PF scrolling looks better if there isn't a lot of difference in the pixels-- i.e., a very gentle upward or downward slope, rather than a large step up or down.

 

Michael

[Thomas Jentzsch]

Do you mean a "jerky" scroll-- i.e., scroll a few PF pixels quickly, then stop scrolling and wait until it's time to scroll a few more PF pixels at once? Scroll, stop, scroll, stop, scroll, etc.?

Yup, that's what I mean.

 

I can see where that would look better (as long as the pauses could be worked into the game), because coarse PF scrolling looks better when it's fast (60 Hz, or 50 Hz for PAL) rather than 1 PF pixel every few frames.

Better scroll with 30/25 Hz which is still fast enough to fool the eye. Else it looks too fast.

[Robert M]

Some games get around the 4 pixel play field problem by not using the play field. Instead they create a strip at the top and bottom of the screen that the game play does not enter. Then they populate those strips with decorative sprites which can be positioned at full horizontal resolution. See Grand Prix by Activision for an example.

Edited September 11, 2010 by Robert M