Orientation of point vs line

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SoCoder -> Snippet Home -> Collisions and Physics

Pakz	Created : 24 November 2019 Language : Monkey2 Orientation of point vs line Is a point left or center or right of a line
#Import "<std>" #Import "<mojo>" Using std.. Using mojo.. Class MyWindow Extends Window Field point1:Vec2i,point2:Vec2i Field point3:Vec2i Field time:Int Method New() newline() End method Method OnRender( canvas:Canvas ) Override App.RequestRender() ' Activate this method time+=1 'draw the line canvas.Color = Color.White canvas.DrawLine(point1,point2) canvas.DrawText("p1",point1.x,point1.y) canvas.DrawText("p2",point2.x,point2.y) canvas.Color = Color.Red canvas.DrawCircle(point3.x,point3.y,20) canvas.Color = Color.Yellow Local side:Int = orientation(point1.x,point1.y,point2.x,point2.y,point3.x,point3.y) Local t:String="point is on the line." If side<0 Then t="Point is on the left side of the line." If side>0 Then t="Point is on the right side of the line." canvas.DrawText(t,0,0) If Keyboard.KeyReleased(Key.Space) Or time>120 Then newline() ; time=0 ' if key escape then quit If Keyboard.KeyReleased(Key.Escape) Then App.Terminate() End Method Method newline() point1 = New Vec2i(Rnd(50,590),Rnd(50,430)) Local x:Int=Rnd(40,90),y:Int=Rnd(40,90) If Rnd()<.5 Then x=-x If Rnd()<.5 Then y=-y point2 = New Vec2i(point1.x+x,point1.y+y) point3 = New Vec2i(Rnd(640),Rnd(480)) End Method End Class ' ' This is the orientation function. It returns -1 if the point is left of the inputted line. ' 0 if on the same and 1 if on the right of the line. ' Function orientation:Int(ax:Int,ay:Int,bx:Int,by:Int,cx:Int,cy:Int) Return Sgn((bx-ax)(cy-ay)-(by-ay)(cx-ax)) End Function Function Main() New AppInstance New MyWindow App.Run() End Function --v
Latest Update This is a example of a function I think is rather useful. The function in here called orientation returns the side of which a point is vs a line. I have not really started testing and using it yet but I think it can be used for instance for rotating a turret or a homing missile towards a target. There are probably a bunch of other use cases. The function returns -1 if the point is left side of a line. 0 if on the center and 1 if on the right. The line direction goes from point1 to point2.

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Orientation of point vs line

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