Friday, March 3, 2017

Monkey-X - Collision - Rectangle vs Rectangle - code example

'  From the book '2d game collision detection'

Import mojo

' This is the collision class. In this example with
' the rectangles collide method.
Class collision
    Method overlapping:Bool(mina:Float,maxa:Float,minb:Float,maxb:Float)
        Return minb <= maxa And mina <= maxb
    End Method
    Method rectangles_collide:Bool(a:rectangle,b:rectangle)
        Local aleft:Float    = a.origin.x
        Local aright:Float    = aleft + a.size.x
        Local bleft:Float    = b.origin.x
        Local bright:Float    = bleft + b.size.x
        Local abottom:Float    = a.origin.y
        Local atop:Float    = abottom + a.size.y
        Local bbottom:Float    = b.origin.y
        Local btop:Float    = bbottom + b.size.y
        Return overlapping(    aleft,aright,
                            bleft,bright) And overlapping(    abottom,
    End Method
End Class

Class vector2d
    ' x and y hold the position of the vector
    Field x:Int,y:Int
    Method New(x:Int,y:Int)
        Self.x = x
        Self.y = y
    End Method
End Class

Class rectangle
    ' origin is a vector that holds the x and y coordinates
    ' of the rectangle
    Field origin:vector2d
    ' size is a vector that holds the x(width) and 
    ' y(height) of the rectangle
    Field size:vector2d
    Method New(origin:vector2d,size:vector2d)
        Self.origin = origin
        Self.size = size
    End Method
    Method draw()
        ' x1,y1,w,h are used to hold the rectangle
        ' location and size.
        Local x1:Int=origin.x
        Local y1:Int=origin.y
        Local w:Int=size.x
        Local h:Int=size.y
        DrawRect x1,y1,w,h
    End Method
End Class

Global col:collision = New collision

Class MyGame Extends App

    Method OnCreate()
    End Method
    Method OnUpdate()        
    End Method
    Method OnRender()
        Cls 0,0,0 
        SetColor 255,255,255
        ' origin is a vector that we use to create
        ' the rectangle. It holds the x and y position.
        Local origin:vector2d=New vector2d(100,200)
        ' size is a vector that we use to create
        ' the rectangle. It holds the width and height.
        Local size:vector2d=New vector2d(100,100)
        ' r1 is a rectangle created with the origin and size
        ' vector variables
        Local r1:rectangle = New rectangle(origin,size)
        ' Here we create another recangle at the 
        ' position of the mouse
        origin = New vector2d(MouseX(),MouseY())
        size = New vector2d(50,50)
        Local r2:rectangle = New rectangle(origin,size)
        If col.rectangles_collide(r1,r2) = True Then
            DrawText "Collision",0,0
            DrawText "No Collision",0,0
        End If
        DrawText "Move the mouse to see if something collides",DeviceWidth/2,0
    End Method
End Class

Function Main()
    New MyGame()
End Function

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