From a03dd460df8bcc5875870031841d67b629a89fc6 Mon Sep 17 00:00:00 2001
From: Jarl Holta <jarlholta@gmail.com>
Date: Sun, 28 Jul 2024 01:18:46 +0200
Subject: [PATCH] Add: IsConvexPolygon

---
 Source/script/imports/simba.import_math.pas | 29 ++++++++++++++++++---
 Source/simba.geometry.pas                   | 25 ++++++++++++++++++
 2 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/Source/script/imports/simba.import_math.pas b/Source/script/imports/simba.import_math.pas
index af31fe233..a33fad7d1 100644
--- a/Source/script/imports/simba.import_math.pas
+++ b/Source/script/imports/simba.import_math.pas
@@ -203,9 +203,27 @@ procedure _LapePolygonArea(const Params: PParamArray; const Result: Pointer); LA
 end;
 
 (*
-PolygonArea
+IsConvexPolygon
+-----------
+> function IsConvexPolygon(Polygon: TPointArray): Boolean;
+
+Returns if the polygon is convex, order does not matter. A concave polygon will return False.
+*)
+procedure _LapeIsConvexPolygon(const Params: PParamArray; const Result: Pointer); LAPE_WRAPPER_CALLING_CONV
+begin
+  PBoolean(Result)^ := TSimbaGeometry.IsConvexPolygon(PPointArray(Params^[0])^);
+end;
+
+(*
+TriangulatePolygon
 -----------
 > function TriangulatePolygon(Polygon: TPointArray): TTriangleArray;
+
+Break the polygon into triangles, the smallest possible polygon. The order of the
+input does matter, if it fails, try to reverse the Poly with Poly.Reversed()
+
+This is a custom algorithm by slacky, based around the concept of trimming "ears",
+if you dont like the output, you may have more luck with rolling the Polygon before calling.
 *)
 procedure _LapeTriangulatePolygon(const Params: PParamArray; const Result: Pointer); LAPE_WRAPPER_CALLING_CONV
 begin
@@ -213,9 +231,11 @@ procedure _LapeTriangulatePolygon(const Params: PParamArray; const Result: Point
 end;
 
 (*
-PolygonArea
+LineInPolygon
 -----------
-> function LineInPolygon(a1, a2: TPoint; const Polygon: TPointArray): Boolean;
+> function LineInPolygon(p,q: TPoint; const Polygon: TPointArray): Boolean;
+
+Returns True if the line fits within the bounds of the polygon.
 *)
 procedure _LapeLineInPolygon(const Params: PParamArray; const Result: Pointer); LAPE_WRAPPER_CALLING_CONV
 begin
@@ -406,7 +426,8 @@ procedure ImportMath(Compiler: TSimbaScript_Compiler);
 
     addGlobalFunc('function Modulo(const X, Y: Integer): Integer; overload', @_LapeModulo);
     addGlobalFunc('function Modulo(const X, Y: Double): Double; overload', @_LapeModuloF);
-  
+    
+    addGlobalFunc('function IsConvexPolygon(const Polygon: TPointArray): Boolean', @_LapeIsConvexPolygon);
     addGlobalFunc('function TriangulatePolygon(const Polygon: TPointArray): TTriangleArray', @_LapeTriangulatePolygon);
     addGlobalFunc('function LineInPolygon(a1, a2: TPoint; const Polygon: TPointArray): Boolean', @_LapeLineInPolygon);
     
diff --git a/Source/simba.geometry.pas b/Source/simba.geometry.pas
index aaf10ffd6..66a362380 100644
--- a/Source/simba.geometry.pas
+++ b/Source/simba.geometry.pas
@@ -11,6 +11,9 @@
   - PointInEllipse
   - AngleBetween
   - DeltaAngle
+  - IsConvexPolygon
+  - LineInPolygon
+  - TriangulatePolygon
 }
 
 {
@@ -43,6 +46,7 @@   TSimbaGeometry = class
   public
     class constructor Create;
 
+    class function IsConvexPolygon(const Polygon: TPointArray): Boolean;
     class function LineInPolygon(a1, a2: TPoint; const Polygon: TPointArray): Boolean;
     class function TriangulatePolygon(Polygon: TPointArray): TTriangleArray;
     class function PolygonArea(const Polygon: TPointArray): Double; static; inline;
@@ -348,6 +352,27 @@ class function TSimbaGeometry.PointInEllipse(const P, Center: TPoint; const YRad
   Result := (Sqr(X) * Sqr(YRadius)) + (Sqr(Y) * Sqr(XRadius)) <= (Sqr(YRadius) * Sqr(XRadius));
 end;
 
+class function TSimbaGeometry.IsConvexPolygon(const Polygon: TPointArray): Boolean;
+var
+  i,d: Int32;
+  a,b,c: TPoint;
+begin
+  if Length(Polygon) = 0 then Exit(False);
+
+  d := CrossProduct(Polygon[i],Polygon[(i+1) mod Length(Polygon)],Polygon[(i+2) mod Length(Polygon)]);
+  for i:=0 to High(Polygon) do
+  begin
+    A := Polygon[i];
+    B := Polygon[(i+1) mod Length(Polygon)];
+    C := Polygon[(i+2) mod Length(Polygon)];
+
+    if CrossProduct(A,B,C)*d <= 0 then
+      Exit(False);
+  end;
+
+  Result := True;
+end;
+
 class function TSimbaGeometry.LineInPolygon(a1, a2: TPoint; const Polygon: TPointArray): Boolean;
 var
   i: Int32;