Sprite Collision - GameCreators Forum

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BeastDeath

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Posted: 30th Nov 2011 16:56 Edited at: 30th Nov 2011 16:57

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Hello everyone, how would I make it so the player would go around the wall and not going through it? The world moves around instead of the player. I have tried some ways but it doesn't seem to work properly, what would everyone else's way of doing this be?

Here's some simple code, how would you add collision so you can go around the wall?

Type Graphics
    id as Integer
    img as Integer
    xpos as Integer
    ypos as Integer
EndType

// Define Variables
Global Player as Graphics
Global Wall as Graphics

// Variables Initialized
Player.id = 2 : Player.img = 2
Player.xpos = Screen Width() / 2 : Player.ypos = Screen Height() / 2

Wall.id = 1 : Wall.img = 1
Wall.xpos = 400 : Wall.ypos = 200

// Load Data
Load Image "player.png", Player.img
Load Image "wall.png", Wall.img

// Sprite Settings - Offset to Center
Sprite Player.id, Player.xpos, Player.ypos, Player.img
Offset Sprite Player.id, Sprite Width(Player.id) / 2, Sprite Height(Player.id) / 2

Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
Offset Sprite Wall.id, Sprite Width(Wall.id) / 2, Sprite Height(Wall.id) / 2

// Setup Code
Sync On : Sync Rate 60 : Autocam Off : Backdrop Off

Do
    
    RenderWorld()
    UpdateWorld()
    
    Sync
Loop

Function RenderWorld()
    
    // re-position Sprite locations
    Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
    
EndFunction

Function UpdateWorld()

// move the entire world instead of the player
    
    If Upkey() then Wall.ypos = Wall.ypos + 1    
    If Downkey() then Wall.ypos = Wall.ypos - 1    
 
    If Leftkey() then Wall.xpos = Wall.xpos + 1
    If Rightkey() then Wall.xpos = Wall.xpos - 1

EndFunction

+ Code Snippet


Type Graphics
    id as Integer
    img as Integer
    xpos as Integer
    ypos as Integer
EndType

// Define Variables
Global Player as Graphics
Global Wall as Graphics

// Variables Initialized
Player.id = 2 : Player.img = 2
Player.xpos = Screen Width() / 2 : Player.ypos = Screen Height() / 2

Wall.id = 1 : Wall.img = 1
Wall.xpos = 400 : Wall.ypos = 200

// Load Data
Load Image "player.png", Player.img
Load Image "wall.png", Wall.img

// Sprite Settings - Offset to Center
Sprite Player.id, Player.xpos, Player.ypos, Player.img
Offset Sprite Player.id, Sprite Width(Player.id) / 2, Sprite Height(Player.id) / 2

Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
Offset Sprite Wall.id, Sprite Width(Wall.id) / 2, Sprite Height(Wall.id) / 2

// Setup Code
Sync On : Sync Rate 60 : Autocam Off : Backdrop Off

Do
    
    RenderWorld()
    UpdateWorld()
    
    Sync
Loop

Function RenderWorld()
    
    // re-position Sprite locations
    Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
    
EndFunction

Function UpdateWorld()

    // move the entire world instead of the player
    
    If Upkey() then Wall.ypos = Wall.ypos + 1    
    If Downkey() then Wall.ypos = Wall.ypos - 1    
 
    If Leftkey() then Wall.xpos = Wall.xpos + 1
    If Rightkey() then Wall.xpos = Wall.xpos - 1    

EndFunction

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zenassem

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Joined: 10th Mar 2003

Location: Long Island, NY

Posted: 30th Nov 2011 17:19 Edited at: 30th Nov 2011 17:21

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For 2d... I would use a tiled-world and a multi-dimensional array (usually 3-5 layers). Do a search for tile worlds, tile, tiled worlds, tiled maps, tile-based, tilebased...(not sure which will yield the best results), to see some examples. After getting down the basics you may want to look up techniques for "smooth scrolling" tile-based maps.

~ZENassem

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MrValentine

AGK Backer

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Playing: FFVII

Posted: 30th Nov 2011 18:07

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Perhaps check as well... The 2D threads...

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basjak

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Posted: 30th Nov 2011 18:18

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so you're trying to create a platform game, you will need plenty of collision points.

my advise to you is to use box 2D, it will make platform games much easier to program.

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BeastDeath

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Posted: 30th Nov 2011 22:23 Edited at: 30th Nov 2011 22:47

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Ok so I've been looking at 2d threads, saying to draw the sprite while a collision check is happening, and to store old locations then moving it back to the old location if a collision has happened, and to do this before the drawing of a sprite. I need to be able to slide around the wall too.

Why doesn't the below code work?

Rem Project: SpriteCollision
Rem Created: Wednesday, November 30, 2011

Rem ***** Main Source File *****
Type Graphics
    id as Integer
    img as Integer
    xpos as Integer
    ypos as Integer
    oldxpos as Integer
    oldypos as Integer
EndType

// Define Variables
Global Player as Graphics
Global Wall as Graphics
Global NotCollided = 0

// Variables Initialized
Player.id = 2 : Player.img = 2
Player.xpos = Screen Width() / 2 : Player.ypos = Screen Height() / 2

Wall.id = 1 : Wall.img = 1
Wall.xpos = 400 : Wall.ypos = 200
Wall.oldxpos = 400 : Wall.oldypos = 200

// Load Data
Load Image "player.png", Player.img
Load Image "wall.png", Wall.img

Draw Sprites First

// Sprite Settings - Offset to Center
Sprite Player.id, Player.xpos, Player.ypos, Player.img
Offset Sprite Player.id, Sprite Width(Player.id) / 2, Sprite Height(Player.id) / 2

Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
Offset Sprite Wall.id, Sprite Width(Wall.id) / 2, Sprite Height(Wall.id) / 2

// Setup Code
Sync On : Sync Rate 60 : Autocam Off : Backdrop Off

Do

UpdateWorld()
    CollisionWorld()

Text 20, 20, "OldX: " + Str$(wall.oldxpos) + " OldY: " + Str$(wall.oldypos)
    Text 20, 40, "X: " + Str$(wall.xpos) + " Y: " + Str$(wall.ypos)

Sync
Loop

Function UpdateWorld()

// move the entire world instead of the player
    // store old sprite locations before moving - used for collision
    
    If Upkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) + 1
    endif
    If Downkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) - 1    
    endif
    If Leftkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) + 1
    Endif
    If Rightkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) - 1    
    endif
    
EndFunction

Function CollisionWorld()

// If I haven't collided, draw the sprite normally.
    If Sprite Collision( player.id , wall.id) = 0
        // Draw Sprite
        Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
    Else
        // If I have collided, move it back to the old locations before drawing the sprite
        If Sprite Collision( player.id , wall.id) = 1
            // Draw Sprite
            Wall.xpos = Wall.oldxpos
            Wall.ypos = Wall.oldypos
            
            Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
            
        EndIf
    EndIf
    
EndFunction

+ Code Snippet

Rem Project: SpriteCollision
Rem Created: Wednesday, November 30, 2011

Rem ***** Main Source File *****
Type Graphics
    id as Integer
    img as Integer
    xpos as Integer
    ypos as Integer
    oldxpos as Integer
    oldypos as Integer
EndType

// Define Variables
Global Player as Graphics
Global Wall as Graphics
Global NotCollided = 0


// Variables Initialized
Player.id = 2 : Player.img = 2
Player.xpos = Screen Width() / 2 : Player.ypos = Screen Height() / 2

Wall.id = 1 : Wall.img = 1
Wall.xpos = 400 : Wall.ypos = 200
Wall.oldxpos = 400 : Wall.oldypos = 200

// Load Data
Load Image "player.png", Player.img
Load Image "wall.png", Wall.img

Draw Sprites First

// Sprite Settings - Offset to Center
Sprite Player.id, Player.xpos, Player.ypos, Player.img
Offset Sprite Player.id, Sprite Width(Player.id) / 2, Sprite Height(Player.id) / 2

Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
Offset Sprite Wall.id, Sprite Width(Wall.id) / 2, Sprite Height(Wall.id) / 2

// Setup Code
Sync On : Sync Rate 60 : Autocam Off : Backdrop Off

Do





    UpdateWorld()
    CollisionWorld()

    Text 20, 20, "OldX: " + Str$(wall.oldxpos) + " OldY: " + Str$(wall.oldypos)
    Text 20, 40, "X: " + Str$(wall.xpos) + " Y: " + Str$(wall.ypos)

    
    Sync
Loop



Function UpdateWorld()

    // move the entire world instead of the player
    // store old sprite locations before moving - used for collision
    
    If Upkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) + 1
    endif
    If Downkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) - 1    
    endif
    If Leftkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) + 1
    Endif
    If Rightkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) - 1    
    endif
    
EndFunction

Function CollisionWorld()

    // If I haven't collided, draw the sprite normally.
    If Sprite Collision( player.id , wall.id) = 0
        // Draw Sprite
        Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
    Else
        // If I have collided, move it back to the old locations before drawing the sprite
        If Sprite Collision( player.id , wall.id) = 1
            // Draw Sprite
            Wall.xpos = Wall.oldxpos
            Wall.ypos = Wall.oldypos
            
            Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
            
        EndIf
    EndIf
    
EndFunction

Thanks for the help

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Chris Tate

DBPro Master

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Joined: 29th Aug 2008

Location: London, England

Posted: 1st Dec 2011 01:09

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Do not put the player in the old position if they collide; instead slide across the direction that has no collision.

In otherwords;

Move left or right; if there is collision; move the opposite way.

Move the player up or down; if there is collision; move the opposite way.

Two dimensions, two collision checks.

Example: If moving towards the bottom right and the collision is to the right, but not down; the player will stop moving right, but will continue moving down; thus sliding down until there is no wall to the right; then the player moves towards the bottom right.

In 3D this works as well; you just do the third collision check; however I have left out how to bounce off of irregular shapes with since this is more complex.

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BeastDeath

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Joined: 7th Jul 2011

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Posted: 1st Dec 2011 23:39

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Hmm I'm not sure what you mean here Chris, a possible code example?

Also how would I do this on per pixel basis, I.E images that are rotated(in the image itself) making some pixels transparent?

Thanks for the help

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Chris Tate

DBPro Master

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Joined: 29th Aug 2008

Location: London, England

Posted: 2nd Dec 2011 00:03 Edited at: 2nd Dec 2011 00:03

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I cannot really test any code right now, so all I can do is edit your code in my web browser.

Old:

Function UpdateWorld()

// move the entire world instead of the player
    // store old sprite locations before moving - used for collision
    
    If Upkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) + 1
    endif
    If Downkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) - 1    
    endif
    If Leftkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) + 1
    Endif
    If Rightkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) - 1    
    endif
    
EndFunction

Function CollisionWorld()

// If I haven't collided, draw the sprite normally.
    If Sprite Collision( player.id , wall.id) = 0
        // Draw Sprite
        Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
    Else
        // If I have collided, move it back to the old locations before drawing the sprite
        If Sprite Collision( player.id , wall.id) = 1
            // Draw Sprite
            Wall.xpos = Wall.oldxpos
            Wall.ypos = Wall.oldypos
            
            Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
            
        EndIf
    EndIf
    
EndFunction

+ Code Snippet

Function UpdateWorld()

    // move the entire world instead of the player
    // store old sprite locations before moving - used for collision
    
    If Upkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) + 1
    endif
    If Downkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) - 1    
    endif
    If Leftkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) + 1
    Endif
    If Rightkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) - 1    
    endif
    
EndFunction

Function CollisionWorld()

    // If I haven't collided, draw the sprite normally.
    If Sprite Collision( player.id , wall.id) = 0
        // Draw Sprite
        Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
    Else
        // If I have collided, move it back to the old locations before drawing the sprite
        If Sprite Collision( player.id , wall.id) = 1
            // Draw Sprite
            Wall.xpos = Wall.oldxpos
            Wall.ypos = Wall.oldypos
            
            Sprite Wall.id, Wall.xpos, Wall.ypos, Wall.img
            
        EndIf
    EndIf
    
EndFunction

New:

+ Code Snippet

Function UpdateWorld()

    // move the entire world instead of the player
    // store old sprite locations before moving - used for collision
    
    If Upkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) + 1
	If Sprite Collision( player.id , wall.id) Then Wall.ypos = Sprite Y(Wall.id) - 1
    endif
    If Downkey()
        wall.oldypos = Sprite Y(wall.id)
        Wall.ypos = Sprite Y(Wall.id) - 1    
	If Sprite Collision( player.id , wall.id) Then Wall.ypos = Sprite Y(Wall.id) + 1
    endif
    If Leftkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) + 1
	If Sprite Collision( player.id , wall.id) Then Wall.ypos = Sprite X(Wall.id) - 1
    Endif
    If Rightkey()
        wall.oldxpos = Sprite X(wall.id)
        Wall.xpos = Sprite X(Wall.id) - 1  
	If Sprite Collision( player.id , wall.id) Then Wall.ypos = Sprite Y(Wall.id) + 1
    endif
    
EndFunction

Now I must say that your code will not work because Sprite Collision is not pixel based. You could split your level up into individual walls and check collision with all of these. Pixel collision is slow and unrecommended unless you have a small world or special code. I recommend Box2d; not that I have used it, due to working in 3d, but from what it says it does and because of who made it, I'd say it should be good for all 2d games like this. Let the engine do the work while you focus on the other aspects.

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BeastDeath

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Joined: 7th Jul 2011

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Posted: 2nd Dec 2011 20:16 Edited at: 2nd Dec 2011 20:18

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(With some minor edits to your code) it seems to work great.

I think I saw a post a while ago which I can't seem to find anymore about collision on the left, right, top and bottom of a sprite, does anyone know how I can test if one of the sides of the player has collided with another sprite?

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Lucas Tiridath

AGK Developer

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Joined: 28th Sep 2008

Location: Kings Langley, UK

Posted: 3rd Dec 2011 03:33

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Hi there. If you're looking for something like pixel perfect without the overhead, you might want to consider line collision. This would also allow you to detect things like the point of contact or the line being hit so you can work out which side a collision is occurring from. I wrote the LineMap plugin to try and make this easier to implement so you might want to have a look and see if it would do what you need. As Chris Tate says, I'm sure Box2D would work great too though. I've not used it in DBP either but it seems pretty good for physics at least in AGK. I'm not sure how you'd work out the direction with that but as I say, I've not used it.

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DarkBASIC Professional Discussion / Sprite Collision