Scratch

berberberber · 2012-06-17 00:45:03

I have seen users like AB3 and Wes64 use this, but I don't understand the mechanics. I know it has to do with stamping, but I don't know how to program it. Can someone help?
Thanks!

SciTecCf · 2012-06-17 04:59:29

Okay, you're going to need a variable called xscroll for the scrolling amount. Then, you need to do this:

when gf clicked
hide //The stamping will do all of the work.
forever
 clear //Remove all previous stamps or pen marks.
 if <<key [left arrow v] pressed?> and <(scrollx) < (0)>>
  change [scrollx v] by (1) //You can change this to 2, 3, 4, or 6.
 end 
 if <<key [right arrow v] pressed?> and <(scrollx) > (-480)>> //Limits scrolling to 480 pixels, or 2 backgrounds.
  change [scrollx v] by (-1) //The same as above, but negative.
 end
 switch to costume [costume1 v] //The first background.
 if <(scrollx) < [480]> //If the first background will be in the screen.
  go to x: (scrollx) y: (0)
  stamp
 end
 switch to costume [costume2 v] //The second background.
 if <(scrollx) > [0]> //If the second background will be in the screen.
  go to x: ((scrollx) + ((480) * (1))) y: (0)
  stamp
 end
end

That's a very basic 2-background scroller. If you want it to be longer, I'll post a solution to that.

berberberber · 2012-06-17 11:29:44

Could you tell me how to extend it?

SciTecCf · 2012-06-17 12:09:20

berberberber wrote:
Could you tell me how to extend it?

Okay!

You start with this:

when gf clicked
hide
forever
 clear
 if <<key [left arrow v] pressed?> and <(scrollx) < (0)>>
  change [scrollx v] by (1) //You can change this to 2, 3, 4, or 6.
 end
 if <<key [right arrow v] pressed?> and <(scrollx) < (960)>> //Set this number to ((your amount of backgrounds minus 1) times 480)
  change [scrollx v] by (-1) //The same as above, but negative.
 end
end

Okay, now, the first one's scripts:

switch to costume [costume1 v] //Your first background.
if <(scrollx) < (-480)>
 go to x: (scrollx) y: (0)
 stamp
end

Add that at the end of the forever loop.
Now, for each of the other ones (except the last one), we need to add this to the end of the forever loop:

switch to costume [costume2 v] //Set this to the correct one.
if <<(scrollx) < (0)> and <(scrollx) > (-960)>> //Change these numbers by -480 for each background.
 go to x: ((scrollx) + ((480) * (1))) y: (0) //Change the 1 by 1 for each background.
 stamp
end

No, finally, for the last one. Just add this to the end of the forever loop:

switch to costume [costume3 v] //Your last background.
if <(scrollx) > (-480)> //Set this to (((amount of backgrounds minus 1) times 480) times -1)
 go to x: ((scrollx) + ((480) * (2))) y: (0) //Set the 2 to the amount of backgrounds - 1.
 stamp
end

All done! I'm sorry if I didn't explain it well. I hope this helps!

IMPORTANT: Test it in Presentation Mode.

Last edited by SciTecCf (2012-06-17 13:47:47)

AtomicBawm3 · 2012-06-17 15:33:52

If you want to extend it into infinite, you should use the "mod" block. Basically, the mod block gives you the remainder after dividing the first number by the second. You have to think about it a bit before it makes sense:
-you want 2 stamps/positions.
-each one must be able to travel from one side to the other and then loop around
next, get into the math:
-since each scene is a full screen (480 pixels long) and the screen is 480 pixels long, in order for it to completely exit the screen on both sides, it must travel from x=480 to x=-480
-480*2=960 is thus the number we will use for the modulus or mod block.

so far we have:

go to x: ((scrollx) mod (960)) y: (0)

but this will make our sprite travel from 960 to 0 and then loop back to 960, so we have to make it:

go to x: (((scrollx) mod (960))-(480)) y: (0)

instead.
There's one of the scenes done, but we need a second in order to keep the screen filled the whole time. Right now we've got one that's going to -480 when scrollx = 0 so you need one going to 0 when scrollx = 0 but also cycles from 480 to -480:

go to x: ((((scrollx)+(480)) mod (960))-(480)) y: (0)

should do the trick.

Last edited by AtomicBawm3 (2012-06-17 15:34:46)

berberberber · 2012-06-17 16:11:27

Thanks, but could you sho me the whole script, AB3?

AtomicBawm3 · 2012-06-17 16:34:58

berberberber wrote:
Thanks, but could you sho me the whole script, AB3?

Sure:

when gf clicked
set [sx v] to (0)
forever
switch to costume 
go to x: (((((sx) * (-1)) + (480)) mod (960)) - (480)) y: (0)
stamp
switch to costume 
go to x: ((((sx)*(-1)) mod (960)) - (480)) y: (0)
stamp

This is what I used for Dark and Light.

Sorry...You can't see the math for the costume numbers:
just odds:
(round(sx/960)*2)+1
Just evens:
(round((sx+480)/960)-1)*2)+2

Last edited by AtomicBawm3 (2012-06-17 16:38:29)

mythbusteranimator · 2012-06-17 17:41:41

Is it something like this?

When gf clicked
forever
 switch to [costume 1 v]
 go to x: (cos1 x) y: (cos1 y)
 stamp
 if <key [right arrow v] pressed
  change [cos1x v] by [1]
 end
 if <key [left arrow v] pressed
  change [cos1 y] by [-1]
 end

And then you just do as many costumes and sensing scripts as you need?

Scratch

archived forums

#1 2012-06-17 00:45:03

1 Sprite Scrolling

#2 2012-06-17 04:59:29

Re: 1 Sprite Scrolling

#3 2012-06-17 11:29:44

Re: 1 Sprite Scrolling

#4 2012-06-17 12:09:20

Re: 1 Sprite Scrolling

berberberber wrote:

#5 2012-06-17 15:33:52

Re: 1 Sprite Scrolling

#6 2012-06-17 16:11:27

Re: 1 Sprite Scrolling

#7 2012-06-17 16:34:58

Re: 1 Sprite Scrolling

berberberber wrote:

#8 2012-06-17 17:41:41

Re: 1 Sprite Scrolling

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