From 88f4552e82021ad66d8f16a18c6669c4d5222726 Mon Sep 17 00:00:00 2001
From: Bergmann89 <info@bergmann89.de>
Date: Wed, 20 Jan 2016 22:21:24 +0100
Subject: [PATCH] * added invert camera position

---
 uglcCamera.pas | 28 ++++++++++++++++++++++++++--
 ugluVector.pas | 15 ++++++++++++++-
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/uglcCamera.pas b/uglcCamera.pas
index 43110d0..396adb0 100644
--- a/uglcCamera.pas
+++ b/uglcCamera.pas
@@ -73,9 +73,15 @@ type
   TglcCamera = class(TglcFrustum)
   private
     fPosition: TgluMatrix4f;
+    fInvertPos: TgluMatrix4f;
+    fInvertValid: Boolean;
+
+    function GetInvertPos: TgluMatrix4f;
     function GetPositionPtr: Pointer;
+    procedure SetPosition(aValue: TgluMatrix4f);
   public
-    property Position:    TgluMatrix4f read fPosition write fPosition;
+    property Position:    TgluMatrix4f read fPosition write SetPosition;
+    property InvertPos:   TgluMatrix4f read GetInvertPos;
     property PositionPtr: Pointer      read GetPositionPtr;
 
     procedure Move(const aVec: TgluVector3f);
@@ -279,6 +285,23 @@ begin
   result := @fPosition[0, 0];
 end;
 
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+function TglcCamera.GetInvertPos: TgluMatrix4f;
+begin
+  if not fInvertValid then begin
+    fInvertValid := true;
+    fInvertPos   := gluMatrixInvert(fPosition);
+  end;
+  result := fInvertPos;
+end;
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+procedure TglcCamera.SetPosition(aValue: TgluMatrix4f);
+begin
+  fPosition    := aValue;
+  fInvertValid := false;
+end;
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 procedure TglcCamera.Move(const aVec: TgluVector3f);
 begin
@@ -339,7 +362,8 @@ end;
 constructor TglcCamera.Create;
 begin
   inherited Create;
-  fPosition := gluMatrixIdentity;
+  fPosition    := gluMatrixIdentity;
+  fInvertValid := false
 end;
 
 end.
diff --git a/ugluVector.pas b/ugluVector.pas
index 61999e4..828dc19 100644
--- a/ugluVector.pas
+++ b/ugluVector.pas
@@ -194,6 +194,7 @@ type
   function gluVectorScalar(const v1, v2: TgluVector2f): Single; overload;
   function gluVectorAngle(const v1, v2: TgluVector3f): Single; overload;
   function gluVectorAngle(const v1, v2: TgluVector2f): Single; overload;
+  function gluVectorAngle2(const v1, v2: TgluVector2f): Single;
   function gluVectorEquals(const v1, v2: TgluVector2f): Boolean; overload;
   function gluVectorEquals(const v1, v2: TgluVector3f): Boolean; overload;
   function gluVectorEquals(const v1, v2: TgluVector4f): Boolean; overload;
@@ -699,12 +700,24 @@ end;
 //Berechnet den Winkel zwischen den übergebenen Vectoren
 //@v1: 1. vektor;
 //@v2: 2. Vektor;
-//@result: Winkel zwischen v1 und v2;
+//@result: Winkel zwischen v1 und v2 im Bereich: (0°; 180°);
 function gluVectorAngle(const v1, v2: TgluVector2f): Single;
 begin
   result := ArcCos(gluVectorScalar(v1, v2)/(gluVectorLength(v1)*gluVectorLength(v2)));
 end;
 
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+//Berechnet den Winkel zwischen den übergebenen Vectoren
+//@v1: 1. vektor;
+//@v2: 2. Vektor;
+//@result: Winkel zwischen v1 und v2 im Bereich: [-180°; 180°) ;
+function gluVectorAngle2(const v1, v2: TgluVector2f): Single;
+begin
+  result := arctan2(
+    v2[0] * v1[1] - v2[1] * v1[0],
+    v2[0] * v1[0] + v2[1] * v1[1]);
+end;
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 function gluVectorEquals(const v1, v2: TgluVector2f): Boolean;
 begin