SuperStrict
Framework BRL.Blitz
Import BRL.GLMax2D
Const CW_ORIENTATION : Int = 1, ..
CCW_ORIENTATION : Int = 2
Global Points : Float[3, 2], ..
A : Float[2], ..
B : Float[2], ..
Orientation : Int
Graphics(640, 480)
While Not KeyDown(KEY_ESCAPE)
Points[0, 0] = Points[1, 0] ; Points[0, 1] = Points[1, 1]
Points[1, 0] = Points[2, 0] ; Points[1, 1] = Points[2, 1]
Points[2, 0] = MouseX() ; Points[2, 1] = MouseY()
Rem
-> |p1.x| |p0.x|
a = |p1.y| - |p0.y|
-> |p2.x| |p1.x|
b = |p2.y| - |p1.y|
-> -> ->
c = a x b
c.z > 0 --> clock wise
c.z <= 0 --> counter clock wise
End Rem
A[0] = Points[1, 0] - Points[0, 0]
A[1] = Points[1, 1] - Points[0, 1]
B[0] = Points[2, 0] - Points[1, 0]
B[1] = Points[2, 1] - Points[1, 1]
If A[0]*B[1] - A[1]*B[0] > 0.0 Then
Orientation = CW_ORIENTATION
Else
Orientation = CCW_ORIENTATION
EndIf
Cls()
If Orientation = CW_ORIENTATION Then
SetColor(255, 0, 0)
Else
SetColor(0, 255, 0)
EndIf
DrawLine(Points[0, 0], Points[0, 1], ..
Points[1, 0], Points[1, 1])
DrawLine(Points[1, 0], Points[1, 1], ..
Points[2, 0], Points[2, 1])
Flip()
Wend
End
Move your mouse very fast clock wise you will see red lines and move it counter clock wise you will see green lines.
The demo do the following:
Tracking 3 points
calculating the cross product
decide, if the cross product vector c "points in or out the monitor"
cu olli
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