Saturday, March 4, 2017

Monkey-X - Collision - Circle vs Point - code example


' From the book '2d game collision detection'
' circle vs point collision

Import mojo

' This is the collision class.
'
Class collision
    ' Collision function
    ' the circle vs point collision
    Method circle_point_collide:Bool(c:circle,p:vector2d)
        Local distance:vector2d = subtract_vector(c.center,p)
        Return vector_length(distance) <= c.radius
    End Method
    ' Helper Functions ........
    '
    '
    Function vector_length:Float(v:vector2d)
        Return Sqrt(v.x * v.x + v.y * v.y)
    End Function

    Function subtract_vector:vector2d(a:vector2d,b:vector2d)
        Local r:vector2d = New vector2d()
        r.x = a.x - b.x
        r.y = a.y - b.y
        Return r
    End Function
    
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 circle
    Field center:vector2d
    Field radius:Float
    Method New(center:vector2d,radius:Float)
        Self.center = center
        Self.radius = radius
    End Method
    Method draw()
        DrawCircle center.x,center.y,radius
    End Method
End Class

' col is the caller of the class collision. 
' we use it to use the collision methods.
Global col:collision = New collision

Class MyGame Extends App
    Method OnCreate()
        SetUpdateRate(30)
    End Method
    Method OnUpdate()  
    End Method
    Method OnRender()
        Cls 0,0,0 
        SetColor 255,255,255

        ' c is a vector where we create the circle with
        Local c:vector2d = New vector2d(320,200)
        ' r is a float variable that is the radius of the circle
        Local r:Float = 100
        ' here we create a circle
        Local circle:circle = New circle(c,r)
        
        ' draw the circle
        circle.draw
        
        ' create a vector at the mouse pointer coordinates
        Local mousevector:vector2d = New vector2d(MouseX,MouseY)
        
        ' test collision
        If col.circle_point_collide(circle,mousevector)
            DrawText "Point Collision with circle",0,0
        Else
            DrawText "Point NO Collision with circle",0,0
        End If
        
        DrawText "Move the mouse around to test collision",DeviceWidth/2,0
    End Method
End Class

Function Main()
    New MyGame()
End Function
    

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