Scratch

Looby wrote:

WOAH!!!! ARCHMAGE! THATS REALLY COMPLICATED!
There is a really simple way of doing it, even with multiple sprites.

It's really not complex. Memorizing 5 lines of code isn't hard.

Hey Archmage thx a lot for the help. I put up a question in the forums about scrolling, and all i got was allot of "go to this" or "view this" or "download this." THANK YOU FOR YOUR HELP!
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I used your tutorial, but found myself how to do it unlimited. For example in my Metal Slug game: [blocks]<when green flag clicked>[/blocks]
                [blocks]<forever if><{ scrollx<(  <<>  )> }>-475[/blocks]
                [blocks]<set{ scrollx }to( 0[/blocks]

Ya, but I memorized your code.

Why not try and use the project how to scroll and download it?     [blocks]<y position>[blocks]

mandarkey wrote:

Why not try and use the project how to scroll and download it?     [blocks]<y position>[blocks]

The tutorial in the forum post uses the same scripts. I also have a few scrolling demos people can download.

Bobby500 wrote:

Hey, archmage, can you tell me how to do this for scrolling?

I want the to be one person in the middle of the screen, multi directional scrollong, like that plane thing of yours. Anyway, when the person when the last terrain is in its view, for it to stop scrolling in that direction and instead have the character be able to walk up the the wall without it scrolling in that direction. So you can't see the backround in a way.
Thanks for the help!

Personally, I would use something like this (note you need very simple backgrounds) http://scratch.mit.edu/forums/viewtopic.php?id=5919 because it dwals with littler numbers. Otherwise, you would have something liek if scroll is less than something your guy doesn't move and scrolls, otherwise he moves

I know this sounds easy to you and I appreciate the help but I am working with and extremly irregular map. I mean it is like

........................
....                   .....
....              .........
                        ......
........................
....                    ......
....

Is there any way so that if it sees the backround or something it will stop scrolling in the direction that the backround is showing?

Last edited by Bobby500 (2008-06-17 20:27:19)

Yeah, pretty much. I just want it to always see the terrain sprites and not the backround.

Thanks I was feeling like like a total ninny not knowing how to scroll

How do I jump?

archmage wrote:

I am going to try and explain how to scroll stuff in scratch but you better be good at programming in scratch before you try this. I do not recommend a scrolling game as your first project.

There are 2 methods of scrolling I use. Method 1 uses many sprites, is easy to implement but can cause lag if the area is too large. Method 2 uses just 2 sprites but does not lag.

METHOD 1: SCROLLING WITH MANY SPRITES
For a demonstration of this method go to http://scratch.mit.edu/projects/archmage/76150

Ok first create a new variable called scrollX

        <{  scrollX  }>

Now that we have that we will need to have our scrolling sprites.
So make a sprite called terrian0.

*It is important to name the sprite terrain0 instead of terrain1 to check and adjust a value used to scroll.*

Now some of these numbers may vary in value depending on the size of your sprite. This assumes your sprite is as wide as the screen.

The number 480 in this code block represents the stage's total width.

//This should be placed on the sprite "terrain0"
<when green flag clicked>

<forever>
<set x to( (( <{ scrollX }>  <+>  ((  480 <*>  0 )) ))

Now the 480 * 0 bit is not necessary in the first sprite you want to scroll but we will keep it in there so we can use it when we duplicate the sprite using the duplicate tool. What that number actually represents is the number at the end of the sprite's name so for the sprite terrain1 you would put

<forever>
<set x to( (( <{ scrollX }>  <+>  ((  480 <*>  1 )) ))

and for terrain2 you would put a 2 instead of a 1 and so on.

Now the number at the end of the sprites name will dictate the order of the sprites so if you keep moving right you will first see terrain1 then terrain2 then terrain3 ect.


now here is a simple script that demonstrates how to alter the scrollX variable to make your sprites scroll.
This code should be placed on the stage. Using this code on multiple sprites is not necessary and not recommended.

<when green flag clicked>

<forever if> <key[ right arrow  ]pressed?>
<change{  scrollX }by( 5


<forever if> <key[ left arrow  ]pressed?>
<change{  scrollX }by( -5

METHOD 2:SCROLLING WITH 2 SPRITES
For a demonstration of this method go to http://scratch.mit.edu/projects/archmage/82995

You should already be comfortable using the first scrolling method as this method is more difficult

You will need to create 3 different variables for this method

  <{  scrollX  }>    //This variables keeps track of how far the user has scrolled

  <{ terrainNum  }>  //This is used to let the terrain sprite know what terrain should be displayed
 
<{  xVelocity  }>  //For some reason I was unable to get linear movement to make the terrain sprite not flicker with this method. However when the scrolling variable is changed according to the xVelocity variable the scrolling works as it should and does not flicker.

*Place these scripts on the stage*

<when green flag clicked>
<forever>
<if>  <( (( <round( <{ scrollX }>  </> 480 )) <>> (( <{ scrollX }>  </> 480 )) )>
<set{ terrainNum }to( (( <round(  (( <{ scrollX }>  </> -480 )) <+> 1 ))
<else>
<set{ terrainNum }to( <round(  (( <{ scrollX }>  </> -480 ))

What this script does is it divides the scroll variable by the stage's width and then rounds it down to the nearest whole number.

<when green flag clicked>
<forever>
<if> <key[ right arrow ]pressed?>
<change{ xVelocity }by( -2
<end>
<if> <key[ left arrow ]pressed?>
<change{ xVelocity }by( 2
<end>
<set{ xVelocity }to(  (( <{ xVelocity }> <*> 0.9  ))
<change{ scrollX }by( <{ xVelocity }>
<end>

This is a basic movement code that uses the xVelocity variable to change the scrollX variable.


Now before we begin programming on the terrain sprites it is very important to remember that BOTH of the two terrain sprites must have exactly the same costumes in exactly the same order. Now doing this will result in weird changing of the terrain sprites to incorrect costumes.

Make sure you have created 2 terrain sprites called "terrain1" and "terrain2".

Now put this code on terrain1.

<when green flag clicked>
<forever>
<switch to costume[ <{ terrainNum }>
<set x to( (( <{ scrollX  }> <+>  (( 480 <*> (( <{ terrainNum }> <-> 1 )) ))))
<end>

What this script does is it sets it's costume according to the terrainNum variable and then it sets it's x position to scrollX+(480*(terrainNum-1)). When the terrainNum variable changes it makes the terrain scripts change costumes accordingly and move to the proper position.

Now put this code on terrain2.

<when green flag clicked>
<forever>
<switch to costume[ (( <{ terrainNum }> <+> 1 ))
<set x to( (( <{ scrollX  }> <+>  (( 480 <*> <{ terrainNum }> ))))
<end>

This script is similar to the script on the first terrain sprite but it has been altered to appear in front of the terrain1 sprite.

Both methods when used correctly will produce a scrolling effect.

If you want to see examples of projects that feature scrolling go to this gallery.
http://scratch.mit.edu/galleries/view/8494

With the help of this and studying the code of your perfect sidescrolling engine, I was able to make a guide partly about it.
http://scratch.mit.edu/projects/Zelda123/200396

and zelda123's versoon as well