Source:CollisionPointTriangle.pb

;Comtois 05/02/05
;Détection d'un point dans un triangle
 
;-Initialisation
Global ScreenHeight.l,ScreenWidth.l
Declare Erreur(Message$)
If ExamineDesktops()
  ScreenWidth = DesktopWidth(0)
  ScreenHeight = DesktopHeight(0)
Else
  Erreur("Euh ?")
EndIf
If InitSprite() = 0 Or InitMouse() = 0 Or InitKeyboard()=0
  Erreur("Impossible d'initialiser DirectX 7 Ou plus")
ElseIf OpenWindow(0,0,0,ScreenWidth,ScreenHeight,#PB_Window_BorderLess,"Collision") = 0
  Erreur("Impossible de créer la fenêtre")
EndIf
;{/ouvre un écran
If OpenWindowedScreen( WindowID(0), 0, 0, ScreenWidth , ScreenHeight, 0, 0, 0 ) = 0
  Erreur("Impossible d'ouvrir l'écran ")
EndIf
 
Structure Triangle
  X1.l
  Y1.l
  X2.l
  Y2.l
  X3.l
  Y3.l
EndStructure
 
Procedure Erreur(Message$)
  MessageRequester( "Erreur" , Message$ , 0 )
  End
EndProcedure
 
Procedure Signe(a.l)
  If a>0
    ProcedureReturn 1
  ElseIf a=0
    ProcedureReturn 0
  Else
    ProcedureReturn -1
  EndIf
EndProcedure
 
Procedure CollisionTriangle(*T.Triangle,*P.point)
  ;Test la collision du point avec le triangle
  ;pour en savoir plus http://tanopah.jo.free.fr/seconde/region.html
  ;Plan 1
  xu1=*T\X2-*T\X1:yu1=*T\Y2-*T\Y1
  c1=*T\Y1*xu1-*T\X1*yu1
  P1=*T\X3*yu1-*T\Y3*xu1+c1
  ax1=*P\x*yu1-*P\y*xu1+c1
  ;Plan 2
  xu2=*T\X3-*T\X2:yu2=*T\Y3-*T\Y2
  c2=*T\Y2*xu2-*T\X2*yu2
  P2=*T\X1*yu2-*T\Y1*xu2+c2
  ax2=*P\x*yu2-*P\y*xu2+c2
  ;Plan 3
  xu3=*T\X1-*T\X3:yu3=*T\Y1-*T\Y3
  c3=*T\Y3*xu3-*T\X3*yu3
  P3=*T\X2*yu3-*T\Y2*xu3+c3
  AX3=*P\x*yu3-*P\y*xu3+c3
 
  If Signe(ax1)=Signe(P1) And Signe(ax2)=Signe(P2) And Signe(AX3)=Signe(P3)
    Resultat=#True
  EndIf
  ProcedureReturn Resultat
EndProcedure
 
Procedure AffPoints(*T.Triangle,*P.point,mem)
  StartDrawing(ScreenOutput())
  ;/Affiche le triangle
  Circle(*T\X1,*T\Y1,4,RGB(255,0,0))
  Circle(*T\X2,*T\Y2,4,RGB(255,0,0))
  Circle(*T\X3,*T\Y3,4,RGB(255,0,0))
  LineXY(*T\X1,*T\Y1,*T\X2,*T\Y2,RGB(255,0,0))
  LineXY(*T\X2,*T\Y2,*T\X3,*T\Y3,RGB(255,0,0))
  LineXY(*T\X1,*T\Y1,*T\X3,*T\Y3,RGB(255,0,0))
  ;/Affiche le point
  If mem
    DrawingMode(4)
    Circle(*P\x,*P\y,6,RGB(255,255,255))
  Else
    DrawingMode(0)
    Circle(*P\x,*P\y,4,RGB(255,255,255))
  EndIf
  ;/Affiche une croix pour mieux suivre le déplacement du point
  LineXY(*P\x,0,*P\x,ScreenHeight-1,RGB(255,255,255))
  LineXY(0,*P\y,ScreenWidth-1,*P\y,RGB(255,255,255))
  Locate(0,0)
  If CollisionTriangle(*T,*P)
    FrontColor(255,255,0)
    BackColor(255,0,0)
    texte$=" IN "
  Else
    FrontColor(155,155,155)
    BackColor(0,255,0)
    texte$=" OUT "
  EndIf
  DrawText(texte$)
  StopDrawing()
EndProcedure
 
Procedure TestPoint(X1,Y1,X2,Y2,d)
  If X1>X2-d And X1<X2+d And Y1>Y2-d And Y1<Y2+d
    Resultat=#True
  EndIf
  ProcedureReturn Resultat
EndProcedure
 
Triangle.Triangle
Point.point
;Triangle modifiable à la souris
Triangle\X1=50
Triangle\Y1=50
Triangle\X2=200
Triangle\Y2=400
Triangle\X3=730
Triangle\Y3=150
;Point à tester
Point\x=340
Point\y=100
DiametreSelection=6
 
Repeat
  While WindowEvent():Wend
  ClearScreen(0, 0, 0)
  ExamineKeyboard()
  ExamineMouse()
  ;Le triangle est modifiable à la souris en cliquant sur un point
  If MouseButton(1)
    If MemPoint=1
      Triangle\X1=MouseX()
      Triangle\Y1=MouseY()
    ElseIf MemPoint=2
      Triangle\X2=MouseX()
      Triangle\Y2=MouseY()
    ElseIf MemPoint=3
      Triangle\X3=MouseX()
      Triangle\Y3=MouseY()
    EndIf
  Else
    MemPoint=0
  EndIf
  If TestPoint(MouseX(),MouseY(),Triangle\X1,Triangle\Y1,DiametreSelection)
    MemPoint=1
  ElseIf TestPoint(MouseX(),MouseY(),Triangle\X2,Triangle\Y2,DiametreSelection)
    MemPoint=2
  ElseIf TestPoint(MouseX(),MouseY(),Triangle\X3,Triangle\Y3,DiametreSelection)
    MemPoint=3
  EndIf
  ;Place le point à tester sous la souris
  Point\x=MouseX()
  Point\y=MouseY()
  ;Affiche le tout
  AffPoints(@Triangle,@Point,MemPoint)
  FlipBuffers()
  Delay(1) 
Until KeyboardPushed(#PB_Key_Escape)