Data commit

Task/Sutherland-Hodgman-polygon-clipping/PureBasic/sutherland-hodgman-polygon-clipping.basic

@@ -0,0 +1,84 @@
+Structure point_f
+  x.f
+  y.f
+EndStructure
+
+Procedure isInside(*p.point_f, *cp1.point_f, *cp2.point_f)
+  If (*cp2\x - *cp1\x) * (*p\y - *cp1\y) > (*cp2\y - *cp1\y) * (*p\x - *cp1\x)
+    ProcedureReturn 1
+  EndIf
+EndProcedure
+
+Procedure intersection(*cp1.point_f, *cp2.point_f, *s.point_f, *e.point_f, *newPoint.point_f)
+  Protected.point_f dc, dp
+  Protected.f n1, n2, n3
+  dc\x = *cp1\x - *cp2\x: dc\y = *cp1\y - *cp2\y
+  dp\x = *s\x - *e\x: dp\y = *s\y - *e\y
+  n1 = *cp1\x * *cp2\y - *cp1\y * *cp2\x
+  n2 = *s\x * *e\y - *s\y * *e\x
+  n3 = 1 / (dc\x * dp\y - dc\y * dp\x)
+  *newPoint\x = (n1 * dp\x - n2 * dc\x) * n3: *newPoint\y = (n1 * dp\y - n2 * dc\y) * n3
+EndProcedure
+
+Procedure clip(List vPolygon.point_f(), List vClippedBy.point_f(), List vClippedPolygon.point_f())
+  Protected.point_f cp1, cp2, s, e, newPoint
+  CopyList(vPolygon(), vClippedPolygon())
+  If LastElement(vClippedBy())
+    cp1 = vClippedBy()
+
+    NewList vPreClipped.point_f()
+    ForEach vClippedBy()
+      cp2 = vClippedBy()
+      CopyList(vClippedPolygon(), vPreClipped())
+      ClearList(vClippedPolygon())
+      If LastElement(vPreClipped())
+        s = vPreClipped()
+        ForEach vPreClipped()
+          e = vPreClipped()
+          If isInside(e, cp1, cp2)
+            If Not isInside(s, cp1, cp2)
+              intersection(cp1, cp2, s, e, newPoint)
+              AddElement(vClippedPolygon()): vClippedPolygon() = newPoint
+            EndIf
+            AddElement(vClippedPolygon()): vClippedPolygon() = e
+          ElseIf isInside(s, cp1, cp2)
+            intersection(cp1, cp2, s, e, newPoint)
+            AddElement(vClippedPolygon()): vClippedPolygon() = newPoint
+          EndIf
+          s = e
+        Next
+      EndIf
+      cp1 = cp2
+    Next
+  EndIf
+EndProcedure
+
+DataSection
+  Data.f 50,150, 200,50, 350,150, 350,300, 250,300, 200,250, 150,350, 100,250, 100,200 ;subjectPolygon's vertices (x,y)
+  Data.f 100,100, 300,100, 300,300, 100,300 ;clipPolygon's vertices (x,y)
+EndDataSection
+
+NewList subjectPolygon.point_f()
+For i = 1 To 9
+  AddElement(subjectPolygon())
+  Read.f subjectPolygon()\x
+  Read.f subjectPolygon()\y
+Next
+
+NewList clipPolygon.point_f()
+For i = 1 To 4
+  AddElement(clipPolygon())
+  Read.f clipPolygon()\x
+  Read.f clipPolygon()\y
+Next
+
+NewList newPolygon.point_f()
+clip(subjectPolygon(), clipPolygon(), newPolygon())
+If OpenConsole()
+  ForEach newPolygon()
+    PrintN("(" + StrF(newPolygon()\x, 2) + ", " + StrF(newPolygon()\y, 2) + ")")
+  Next
+
+  Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
+  CloseConsole()
+EndIf