Does two-way scrolling work at present?

Goaterby

Member
I set up a scrolling platformer module project using many of the new tutorial platformer assets and made 3 test screens, setting them all to scroll in both directions without edge blocking, and using gravity. Movement and scrolling etc seemed to work normally at first, but if you add elements of any kind that are solid towards the edge of each screen in the editor (like a 1 tile high wall on top of the floor, for instance), these attributes will invisibly apply to the edge of the screen before it, and sometimes going back and forth between the areas will lead to a column of tiles disappearing or palette swapping in a weird way.

This all being said, is two-way scrolling (just left and right) for sure supported in 4.1? I saw a video preview of it on the facebook group but it was brief and lacked an explanation, so I didn't know if these things I was attempting out of the box were even supposed to be working.


EDIT: Dur, I didn't look at their site close enough. In the unlisted youtube video for the scrolling tutorial, Joe states that two-way / bidirectional scrolling is not fully functional at present, and will likely exhibit bugs and strange things if used.

Thus far the only bugs I have found (if other people want to mess with it), apart from some odd palette stuff here and there sometimes, is that going back and forth, as mentioned above, changes the edges of the screens to include collision data from the opposite side. You can get around this in level design no problem so long as tall things are not on the edges of each screen boundary, but if you have changing attributes or other custom stuff it might not work out.
 

Mugi

Member
short answer: no, it is not.

longer answer:
as Joe specifically said in the videos that accompanied the launch of 4.1.0, the module CAN do 2-directional scrolling, but is explicitly designed to only scroll into one direction (right.)
the checkboxes in screen settings are there, so that you can make it scroll in 2 directions but the scrolling code does not fully handle that yet, thus it just completely breaks the collision tables, and incorrectly purges the tables for room data, leading into the fact that when you change scrolling direction mid-room, the room where you just came from will completely corrupt.
so as far as that goes, at the moment, if you want 2-directional scrolling, get ready to go knee-deep in advanced assembly code. That said, the fact that the option is there and *works* just demonstrates that it is indeed very possible. Here's to hoping that a more functional implementation of it follows, maybe in a more platformer specified module update instead of these all-around updates.

I'm pretty sure that people will dig into that code sooner or later (i've been analyzing the scroll code for some hours now myself) and i have no doubts that it will become functional, but as for now, it is not.
 

darkhog

New member
Aside of stuff like pickups (both tile and sprite-based) respawning, I haven't noticed any major glitches. and plenty of actual NES games had respawning pickups issue when you were far enough from the screen, to the point that in some you could cheese stuff like get extra 1ups you shouldn't be able to get if you decide to go back to the start of the level after getting almost to the end.
 
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