Dim triangle#(2, 1), point#(1)

triangle#(0, 0) = 400.0 : triangle#(0, 1) = 150.0
triangle#(1, 0) = 200.0 : triangle#(1, 1) = 400.0
triangle#(2, 0) = 600.0 : triangle#(2, 1) = 400.0

Graphics 800, 600, 0, 2
SetBuffer BackBuffer()

While Not KeyDown(1)
	Cls()
	
	point(0) = MouseX() : point(1) = MouseY()
	If TestPointInTriangle%() Then
		Color 255, 0, 0
	Else
		Color 255, 255, 0
	EndIf
	
	
	DrawTestCase()
	Flip()
Wend

End

Function DrawTestCase()
	For I = 0 To 2
		Oval triangle#(I, 0)-2, triangle#(I, 1)-2, 5, 5
	Next
	For I = 0 To 2
		Local edgeA = I, edgeB = (I + 1) Mod 3
		Line triangle#(edgeA, 0), triangle#(edgeA, 1), triangle#(edgeB, 0), triangle#(edgeB, 1)
	Next
	
	Oval point(0)-2, point(1)-2, 5, 5
End Function

Function TestPointInTriangle%()
	Local b1%, b2%, b3%
	
	b1% = Sign(point(0), point(1), triangle(0, 0), triangle(0, 1), triangle(1, 0), triangle(1, 1)) < 0.0
	b2% = Sign(point(0), point(1), triangle(1, 0), triangle(1, 1), triangle(2, 0), triangle(2, 1)) < 0.0
	b3% = Sign(point(0), point(1), triangle(2, 0), triangle(2, 1), triangle(0, 0), triangle(0, 1)) < 0.0
	
	Return (b1 = b2) And (b2 = b3)
End Function

Function Sign#(x1#, y1#, x2#, y2#, x3#, y3#)
	Return (x1# - x3#)*(y2# - y3#) - (x2# - x3#)*(y1# - y3#)
End Function

SuperStrict

Graphics 640,480,0,50

Type tPoint
	Field x:Float, y:Float
	
	Method Set(x:Float, y:Float)
		Self.x = x
		Self.y = y
	EndMethod
EndType

Type tTri
	Field p1:tPoint=New tPoint, p2:tPoint=New tPoint, p3:tPoint=New tPoint
	
	Method Draw()
		DrawLine(Self.p1.x, Self.p1.y, Self.p2.x, Self.p2.y)
		DrawLine(Self.p2.x, Self.p2.y, Self.p3.x, Self.p3.y)
		DrawLine(Self.p1.x, Self.p1.y, Self.p3.x, Self.p3.y)
	EndMethod
EndType


Function Sign:Float(p1:tPoint, p2:tPoint, p3:tPoint)
	Return (p1.x - p3.x) * (p2.y - p3.y) - (p2.x - p3.x) * (p1.y - p3.y)
EndFunction

Function PointInTri:Byte(pt:tPoint, tri:tTri)
	Local b1:Byte, b2:Byte, b3:Byte
	b1 = Sign(pt, tri.p1, tri.p2) < 0.0
	b2 = Sign(pt, tri.p2, tri.p3) < 0.0
	b3 = Sign(pt, tri.p3, tri.p1) < 0.0
	Return ((b1 = b2) & (b2 = b3))
EndFunction



Local tri1:tTri = New tTri
tri1.p1.Set(100, 100)
tri1.p2.Set(100, 200)
tri1.p3.Set(300, 100)

While Not AppTerminate()
	tri1.Draw()
	Local mouse:tPoint = New tPoint
	mouse.Set(MouseX(), MouseY())
	DrawText("Point in Triangle? --> "+(PointInTri(mouse, tri1)), 1, 1)	
	Flip;Cls	
Wend