Use vertical instead of horizontal FOV in HMM_Perspective (#101)

* Use vertical instead of horizontal FOV

* Update readme

* Fix tests

HandmadeMath.h

@@ -1,5 +1,5 @@
 /*
-  HandmadeMath.h v1.7.0
+  HandmadeMath.h v1.9.0
   
   This is a single header file with a bunch of useful functions for game and
   graphics math operations.
@@ -65,118 +65,6 @@
   versions of these functions that are provided by the CRT.
   
   =============================================================================
-  
-  Version History:
-      0.2 (*) Updated documentation
-          (*) Better C compliance
-          (*) Prefix all handmade math functions 
-          (*) Better operator overloading
-      0.2a
-          (*) Prefixed Macros
-      0.2b
-          (*) Disabled warning 4201 on MSVC as it is legal is C11
-          (*) Removed the f at the end of HMM_PI to get 64bit precision
-      0.3
-          (*) Added +=, -=, *=, /= for hmm_vec2, hmm_vec3, hmm_vec4
-      0.4
-          (*) SSE Optimized HMM_SqrtF
-          (*) SSE Optimized HMM_RSqrtF
-          (*) Removed CRT
-      0.5
-          (*) Added scalar multiplication and division for vectors
-              and matrices
-          (*) Added matrix subtraction and += for hmm_mat4
-          (*) Reconciled all headers and implementations
-          (*) Tidied up, and filled in a few missing operators
-      0.5.1
-          (*) Ensured column-major order for matrices throughout
-          (*) Fixed HMM_Translate producing row-major matrices
-      0.5.2
-          (*) Fixed SSE code in HMM_SqrtF
-          (*) Fixed SSE code in HMM_RSqrtF
-      0.6
-          (*) Added Unit testing
-          (*) Made HMM_Power faster
-          (*) Fixed possible efficiency problem with HMM_Normalize 
-          (*) RENAMED HMM_LengthSquareRoot to HMM_LengthSquared
-          (*) RENAMED HMM_RSqrtF to HMM_RSquareRootF
-          (*) RENAMED HMM_SqrtF to HMM_SquareRootF
-          (*) REMOVED Inner function (user should use Dot now)
-          (*) REMOVED HMM_FastInverseSquareRoot function declaration
-      0.7 
-          (*) REMOVED HMM_LengthSquared in HANDMADE_MATH_IMPLEMENTATION (should
-              use HMM_LengthSquaredVec3, or HANDMADE_MATH_CPP_MODE for function
-              overloaded version)
-          (*) REMOVED HMM_Length in HANDMADE_MATH_IMPLEMENTATION (should use
-              HMM_LengthVec3, HANDMADE_MATH_CPP_MODE for function
-              overloaded version)
-          (*) REMOVED HMM_Normalize in HANDMADE_MATH_IMPLEMENTATION (should use
-              HMM_NormalizeVec3, or HANDMADE_MATH_CPP_MODE for function
-              overloaded version)
-          (*) Added HMM_LengthSquaredVec2
-          (*) Added HMM_LengthSquaredVec4
-          (*) Addd HMM_LengthVec2
-          (*) Added HMM_LengthVec4
-          (*) Added HMM_NormalizeVec2
-          (*) Added HMM_NormalizeVec4
-     1.0
-          (*) Lots of testing!
-     1.1
-          (*) Quaternion support
-          (*) Added type hmm_quaternion
-          (*) Added HMM_Quaternion
-          (*) Added HMM_QuaternionV4
-          (*) Added HMM_AddQuaternion
-          (*) Added HMM_SubtractQuaternion
-          (*) Added HMM_MultiplyQuaternion
-          (*) Added HMM_MultiplyQuaternionF
-          (*) Added HMM_DivideQuaternionF
-          (*) Added HMM_InverseQuaternion
-          (*) Added HMM_DotQuaternion
-          (*) Added HMM_NormalizeQuaternion
-          (*) Added HMM_Slerp
-          (*) Added HMM_QuaternionToMat4
-          (*) Added HMM_QuaternionFromAxisAngle
-     1.1.1
-          (*) Resolved compiler warnings on gcc and g++
-     1.1.2
-          (*) Fixed invalid HMMDEF's in the function definitions
-     1.1.3
-          (*) Fixed compile error in C mode
-     1.1.4
-          (*) Fixed SSE being included on platforms that don't support it
-          (*) Fixed divide-by-zero errors when normalizing zero vectors.
-     1.1.5
-          (*) Add Width and Height to HMM_Vec2
-          (*) Made it so you can supply your own SqrtF 
-     1.2.0
-          (*) Added equality functions for HMM_Vec2, HMM_Vec3, and HMM_Vec4.
-              (*) Added HMM_EqualsVec2, HMM_EqualsVec3, and HMM_EqualsVec4
-              (*) Added C++ overloaded HMM_Equals for all three
-              (*) Added C++ == and != operators for all three
-          (*) SSE'd HMM_MultiplyMat4 (this is _WAY_ faster)
-          (*) SSE'd HMM_Transpose
-     1.3.0
-          (*) Remove need to #define HANDMADE_MATH_CPP_MODE
-     1.4.0
-          (*) Fixed bug when using HandmadeMath in C mode
-          (*) SSEd all vec4 operations          
-          (*) Removed all zero-ing
-     1.5.0
-          (*) Changed internal structure for better performance and inlining.
-          (*) As a result, HANDMADE_MATH_NO_INLINE has been removed and no
-              longer has any effect.
-     1.5.1
-          (*) Fixed a bug with uninitialized elements in HMM_LookAt.
-     1.6.0
-          (*) Added array subscript operators for vector and matrix types in
-              C++. This is provided as a convenience, but be aware that it may
-              incur an extra function call in unoptimized builds.
-     1.7.0
-          (*) Renamed the 'Rows' member of hmm_mat4 to 'Columns'. Since our
-              matrices are column-major, this should have been named 'Columns'
-              from the start. 'Rows' is still present, but has been deprecated.
-
 
   LICENSE
   
@@ -195,6 +83,7 @@
    Gingerbill (@TheGingerBill)
    Ben Visness (@bvisness) 
    Trinton Bullard (@Peliex_Dev)
+   @AntonDan
    
   Fixes:
    Jeroen van Rijn (@J_vanRijn)
@@ -324,7 +213,7 @@ typedef union hmm_vec2
     float Elements[2];
 
 #ifdef __cplusplus
-    inline float &operator[](int Index)
+    inline float &operator[](const int &Index)
     {
         return Elements[Index];
     }
@@ -375,7 +264,7 @@ typedef union hmm_vec3
     float Elements[3];
 
 #ifdef __cplusplus
-    inline float &operator[](int Index)
+    inline float &operator[](const int &Index)
     {
         return Elements[Index];
     }
@@ -439,7 +328,7 @@ typedef union hmm_vec4
 #endif
 
 #ifdef __cplusplus
-    inline float &operator[](int Index)
+    inline float &operator[](const int &Index)
     {
         return Elements[Index];
     }
@@ -459,7 +348,7 @@ typedef union hmm_mat4
 #endif
 
 #ifdef __cplusplus
-    inline hmm_vec4 operator[](const int Index)
+    inline hmm_vec4 operator[](const int &Index)
     {
         float* col = Elements[Index];
 
@@ -491,6 +380,10 @@ typedef union hmm_quaternion
     };
     
     float Elements[4];
+
+#ifdef HANDMADE_MATH__USE_SSE    
+    __m128 InternalElementsSSE;
+#endif
 } hmm_quaternion;
 
 typedef int32_t hmm_bool;
@@ -1128,6 +1021,21 @@ HMM_INLINE hmm_vec4 HMM_NormalizeVec4(hmm_vec4 A)
     return (Result);
 }
 
+HMM_INLINE hmm_vec2 HMM_FastNormalizeVec2(hmm_vec2 A)
+{
+    return HMM_MultiplyVec2f(A, HMM_RSquareRootF(HMM_DotVec2(A, A)));
+}
+
+HMM_INLINE hmm_vec3 HMM_FastNormalizeVec3(hmm_vec3 A)
+{
+    return HMM_MultiplyVec3f(A, HMM_RSquareRootF(HMM_DotVec3(A, A)));
+}
+
+HMM_INLINE hmm_vec4 HMM_FastNormalizeVec4(hmm_vec4 A)
+{
+    return HMM_MultiplyVec4f(A, HMM_RSquareRootF(HMM_DotVec4(A, A)));
+}
+
 
 /*
  * SSE stuff
@@ -1278,10 +1186,12 @@ HMM_INLINE hmm_mat4 HMM_Perspective(float FOV, float AspectRatio, float Near, fl
 {
     hmm_mat4 Result = HMM_Mat4();
 
-    float TanThetaOver2 = HMM_TanF(FOV * (HMM_PI32 / 360.0f));
+    // See https://www.khronos.org/registry/OpenGL-Refpages/gl2.1/xhtml/gluPerspective.xml
+
+    float Cotangent = 1.0f / HMM_TanF(FOV * (HMM_PI32 / 360.0f));
     
-    Result.Elements[0][0] = 1.0f / TanThetaOver2;
-    Result.Elements[1][1] = AspectRatio / TanThetaOver2;
+    Result.Elements[0][0] = Cotangent / AspectRatio;
+    Result.Elements[1][1] = Cotangent;
     Result.Elements[2][3] = -1.0f;
     Result.Elements[2][2] = (Near + Far) / (Near - Far);
     Result.Elements[3][2] = (2.0f * Near * Far) / (Near - Far);
@@ -1325,10 +1235,14 @@ HMM_INLINE hmm_quaternion HMM_Quaternion(float X, float Y, float Z, float W)
 {
     hmm_quaternion Result;
 
+#ifdef HANDMADE_MATH__USE_SSE
+    Result.InternalElementsSSE = _mm_setr_ps(X, Y, Z, W);
+#else
     Result.X = X;
     Result.Y = Y;
     Result.Z = Z;
     Result.W = W;
+#endif
 
     return (Result);
 }
@@ -1337,10 +1251,14 @@ HMM_INLINE hmm_quaternion HMM_QuaternionV4(hmm_vec4 Vector)
 {
     hmm_quaternion Result;
 
+#ifdef HANDMADE_MATH__USE_SSE
+    Result.InternalElementsSSE = Vector.InternalElementsSSE;
+#else
     Result.X = Vector.X;
     Result.Y = Vector.Y;
     Result.Z = Vector.Z;
     Result.W = Vector.W;
+#endif
 
     return (Result);
 }
@@ -1349,10 +1267,15 @@ HMM_INLINE hmm_quaternion HMM_AddQuaternion(hmm_quaternion Left, hmm_quaternion
 {
     hmm_quaternion Result;
 
+#ifdef HANDMADE_MATH__USE_SSE
+    Result.InternalElementsSSE = _mm_add_ps(Left.InternalElementsSSE, Right.InternalElementsSSE);
+#else
+
     Result.X = Left.X + Right.X;
     Result.Y = Left.Y + Right.Y;
     Result.Z = Left.Z + Right.Z;
     Result.W = Left.W + Right.W;
+#endif
 
     return (Result);
 }
@@ -1361,10 +1284,15 @@ HMM_INLINE hmm_quaternion HMM_SubtractQuaternion(hmm_quaternion Left, hmm_quater
 {
     hmm_quaternion Result;
 
+#ifdef HANDMADE_MATH__USE_SSE
+    Result.InternalElementsSSE = _mm_sub_ps(Left.InternalElementsSSE, Right.InternalElementsSSE);
+#else
+
     Result.X = Left.X - Right.X;
     Result.Y = Left.Y - Right.Y;
     Result.Z = Left.Z - Right.Z;
     Result.W = Left.W - Right.W;
+#endif
 
     return (Result);
 }
@@ -1373,10 +1301,28 @@ HMM_INLINE hmm_quaternion HMM_MultiplyQuaternion(hmm_quaternion Left, hmm_quater
 {
     hmm_quaternion Result;
 
+#ifdef HANDMADE_MATH__USE_SSE
+        __m128 SSEResultOne = _mm_xor_ps(_mm_shuffle_ps(Left.InternalElementsSSE, Left.InternalElementsSSE, _MM_SHUFFLE(0, 0, 0, 0)), _mm_setr_ps(0.f, -0.f, 0.f, -0.f));
+        __m128 SSEResultTwo = _mm_shuffle_ps(Right.InternalElementsSSE, Right.InternalElementsSSE, _MM_SHUFFLE(0, 1, 2, 3));
+        __m128 SSEResultThree = _mm_mul_ps(SSEResultTwo, SSEResultOne);
+
+        SSEResultOne = _mm_xor_ps(_mm_shuffle_ps(Left.InternalElementsSSE, Left.InternalElementsSSE, _MM_SHUFFLE(1, 1, 1, 1)) , _mm_setr_ps(0.f, 0.f, -0.f, -0.f));
+        SSEResultTwo = _mm_shuffle_ps(Right.InternalElementsSSE, Right.InternalElementsSSE, _MM_SHUFFLE(1, 0, 3, 2));
+        SSEResultThree = _mm_add_ps(SSEResultThree, _mm_mul_ps(SSEResultTwo, SSEResultOne));
+
+        SSEResultOne = _mm_xor_ps(_mm_shuffle_ps(Left.InternalElementsSSE, Left.InternalElementsSSE, _MM_SHUFFLE(2, 2, 2, 2)), _mm_setr_ps(-0.f, 0.f, 0.f, -0.f));
+        SSEResultTwo = _mm_shuffle_ps(Right.InternalElementsSSE, Right.InternalElementsSSE, _MM_SHUFFLE(2, 3, 0, 1));
+        SSEResultThree = _mm_add_ps(SSEResultThree, _mm_mul_ps(SSEResultTwo, SSEResultOne));
+
+        SSEResultOne = _mm_shuffle_ps(Left.InternalElementsSSE, Left.InternalElementsSSE, _MM_SHUFFLE(3, 3, 3, 3));
+        SSEResultTwo = _mm_shuffle_ps(Right.InternalElementsSSE, Right.InternalElementsSSE, _MM_SHUFFLE(3, 2, 1, 0));
+        Result.InternalElementsSSE = _mm_add_ps(SSEResultThree, _mm_mul_ps(SSEResultTwo, SSEResultOne));
+#else
     Result.X = (Left.X * Right.W) + (Left.Y * Right.Z) - (Left.Z * Right.Y) + (Left.W * Right.X);
     Result.Y = (-Left.X * Right.Z) + (Left.Y * Right.W) + (Left.Z * Right.X) + (Left.W * Right.Y);
     Result.Z = (Left.X * Right.Y) - (Left.Y * Right.X) + (Left.Z * Right.W) + (Left.W * Right.Z);
     Result.W = (-Left.X * Right.X) - (Left.Y * Right.Y) - (Left.Z * Right.Z) + (Left.W * Right.W);
+#endif
 
     return (Result);
 }
@@ -1385,10 +1331,15 @@ HMM_INLINE hmm_quaternion HMM_MultiplyQuaternionF(hmm_quaternion Left, float Mul
 {
     hmm_quaternion Result;
 
+#ifdef HANDMADE_MATH__USE_SSE
+    __m128 Scalar = _mm_set1_ps(Multiplicative);
+    Result.InternalElementsSSE = _mm_mul_ps(Left.InternalElementsSSE, Scalar);
+#else
     Result.X = Left.X * Multiplicative;
     Result.Y = Left.Y * Multiplicative;
     Result.Z = Left.Z * Multiplicative;
     Result.W = Left.W * Multiplicative;
+#endif
 
     return (Result);
 }
@@ -1397,10 +1348,15 @@ HMM_INLINE hmm_quaternion HMM_DivideQuaternionF(hmm_quaternion Left, float Divid
 {
     hmm_quaternion Result;
 
+#ifdef HANDMADE_MATH__USE_SSE
+    __m128 Scalar = _mm_set1_ps(Dividend);
+    Result.InternalElementsSSE = _mm_div_ps(Left.InternalElementsSSE, Scalar);
+#else
     Result.X = Left.X / Dividend;
     Result.Y = Left.Y / Dividend;
     Result.Z = Left.Z / Dividend;
     Result.W = Left.W / Dividend;
+#endif
 
     return (Result);
 }
@@ -1409,7 +1365,18 @@ HMM_EXTERN hmm_quaternion HMM_InverseQuaternion(hmm_quaternion Left);
 
 HMM_INLINE float HMM_DotQuaternion(hmm_quaternion Left, hmm_quaternion Right)
 {
-    float Result = (Left.X * Right.X) + (Left.Y * Right.Y) + (Left.Z * Right.Z) + (Left.W * Right.W);
+    float Result;
+
+#ifdef HANDMADE_MATH__USE_SSE
+    __m128 SSEResultOne = _mm_mul_ps(Left.InternalElementsSSE, Right.InternalElementsSSE);
+    __m128 SSEResultTwo = _mm_shuffle_ps(SSEResultOne, SSEResultOne, _MM_SHUFFLE(2, 3, 0, 1));
+    SSEResultOne = _mm_add_ps(SSEResultOne, SSEResultTwo);
+    SSEResultTwo = _mm_shuffle_ps(SSEResultOne, SSEResultOne, _MM_SHUFFLE(0, 1, 2, 3));
+    SSEResultOne = _mm_add_ps(SSEResultOne, SSEResultTwo);
+    _mm_store_ss(&Result, SSEResultOne);
+#else
+    Result = (Left.X * Right.X) + (Left.Y * Right.Y) + (Left.Z * Right.Z) + (Left.W * Right.W);
+#endif
 
     return (Result);
 }
@@ -1428,11 +1395,18 @@ HMM_INLINE hmm_quaternion HMM_NLerp(hmm_quaternion Left, float Time, hmm_quatern
 {
     hmm_quaternion Result;
 
+#ifdef HANDMADE_MATH__USE_SSE
+    __m128 ScalarLeft = _mm_set1_ps(1.0f - Time);
+    __m128 ScalarRight = _mm_set1_ps(Time);
+    __m128 SSEResultOne = _mm_mul_ps(Left.InternalElementsSSE, ScalarLeft);
+    __m128 SSEResultTwo = _mm_mul_ps(Right.InternalElementsSSE, ScalarRight);
+    Result.InternalElementsSSE = _mm_add_ps(SSEResultOne, SSEResultTwo);
+#else
     Result.X = HMM_Lerp(Left.X, Time, Right.X);
     Result.Y = HMM_Lerp(Left.Y, Time, Right.Y);
     Result.Z = HMM_Lerp(Left.Z, Time, Right.Z);
     Result.W = HMM_Lerp(Left.W, Time, Right.W);
-
+#endif
     Result = HMM_NormalizeQuaternion(Result);
 
     return (Result);
@@ -1511,6 +1485,27 @@ HMM_INLINE hmm_vec4 HMM_Normalize(hmm_vec4 A)
     return (Result);
 }
 
+HMM_INLINE hmm_vec2 HMM_FastNormalize(hmm_vec2 A)
+{
+    hmm_vec2 Result = HMM_FastNormalizeVec2(A);
+
+    return (Result);
+}
+
+HMM_INLINE hmm_vec3 HMM_FastNormalize(hmm_vec3 A)
+{
+    hmm_vec3 Result = HMM_FastNormalizeVec3(A);
+
+    return (Result);
+}
+
+HMM_INLINE hmm_vec4 HMM_FastNormalize(hmm_vec4 A)
+{
+    hmm_vec4 Result = HMM_FastNormalizeVec4(A);
+
+    return (Result);
+}
+
 HMM_INLINE hmm_quaternion HMM_Normalize(hmm_quaternion A)
 {
     hmm_quaternion Result = HMM_NormalizeQuaternion(A);
@@ -2419,10 +2414,7 @@ hmm_quaternion HMM_InverseQuaternion(hmm_quaternion Left)
     Norm = HMM_SquareRootF(HMM_DotQuaternion(Left, Left));
     NormSquared = Norm * Norm;
 
-    Result.X = Conjugate.X / NormSquared;
-    Result.Y = Conjugate.Y / NormSquared;
-    Result.Z = Conjugate.Z / NormSquared;
-    Result.W = Conjugate.W / NormSquared;
+    Result = HMM_DivideQuaternionF(Conjugate, NormSquared);
 
     return (Result);
 }

README.md

@@ -10,6 +10,10 @@ To get started, go download [the latest release](https://github.com/HandmadeMath
 
 Version         | Changes        |
 ----------------|----------------|
+**1.10.0** | Made HMM_Perspective use vertical FOV instead of horizontal FOV for consistency with other graphics APIs. |
+**1.9.0** | Added SSE versions of quaternion operations. |
+**1.8.0** | Added fast vector normalization routines that use fast inverse square roots.
+**1.7.1** | Changed operator[] to take a const ref int instead of an int.
 **1.7.0** | Renamed the 'Rows' member of hmm_mat4 to 'Columns'. Since our matrices are column-major, this should have been named 'Columns' from the start. 'Rows' is still present, but has been deprecated.
 **1.6.0** | Added array subscript operators for vector and matrix types in C++. This is provided as a convenience, but be aware that it may incur an extra function call in unoptimized builds.
 **1.5.1** | Fixed a bug with uninitialized elements in HMM_LookAt.

test/categories/Projection.h

@@ -20,16 +20,16 @@ TEST(Projection, Perspective)
     {
         hmm_vec3 original = HMM_Vec3(5.0f, 5.0f, -15.0f);
         hmm_vec4 projected = HMM_MultiplyMat4ByVec4(projection, HMM_Vec4v(original, 1));
-        EXPECT_FLOAT_EQ(projected.X, 5.0f);
-        EXPECT_FLOAT_EQ(projected.Y, 10.0f);
+        EXPECT_FLOAT_EQ(projected.X, 2.5f);
+        EXPECT_FLOAT_EQ(projected.Y, 5.0f);
         EXPECT_FLOAT_EQ(projected.Z, 15.0f);
         EXPECT_FLOAT_EQ(projected.W, 15.0f);
     }
     {
         hmm_vec3 original = HMM_Vec3(5.0f, 5.0f, -5.0f);
         hmm_vec4 projected = HMM_MultiplyMat4ByVec4(projection, HMM_Vec4v(original, 1));
-        EXPECT_FLOAT_EQ(projected.X, 5.0f);
-        EXPECT_FLOAT_EQ(projected.Y, 10.0f);
+        EXPECT_FLOAT_EQ(projected.X, 2.5f);
+        EXPECT_FLOAT_EQ(projected.Y, 5.0f);
         EXPECT_FLOAT_EQ(projected.Z, -5.0f);
         EXPECT_FLOAT_EQ(projected.W, 5.0f);
     }

test/categories/VectorOps.h

@@ -134,6 +134,106 @@ TEST(VectorOps, NormalizeZero)
 #endif
 }
 
+TEST(VectorOps, FastNormalize)
+{
+    hmm_vec2 v2 = HMM_Vec2(1.0f, -2.0f);
+    hmm_vec3 v3 = HMM_Vec3(1.0f, -2.0f, 3.0f);
+    hmm_vec4 v4 = HMM_Vec4(1.0f, -2.0f, 3.0f, -1.0f);
+
+    {
+        hmm_vec2 result = HMM_FastNormalizeVec2(v2);
+        EXPECT_NEAR(HMM_LengthVec2(result), 1.0f, 0.001f);
+        EXPECT_GT(result.X, 0.0f);
+        EXPECT_LT(result.Y, 0.0f);
+    }
+    {
+        hmm_vec3 result = HMM_FastNormalizeVec3(v3);
+        EXPECT_NEAR(HMM_LengthVec3(result), 1.0f, 0.001f);
+        EXPECT_GT(result.X, 0.0f);
+        EXPECT_LT(result.Y, 0.0f);
+        EXPECT_GT(result.Z, 0.0f);
+    }
+    {
+        hmm_vec4 result = HMM_FastNormalizeVec4(v4);
+        EXPECT_NEAR(HMM_LengthVec4(result), 1.0f, 0.001f);
+        EXPECT_GT(result.X, 0.0f);
+        EXPECT_LT(result.Y, 0.0f);
+        EXPECT_GT(result.Z, 0.0f);
+        EXPECT_LT(result.W, 0.0f);
+    }
+
+#ifdef __cplusplus
+    {
+        hmm_vec2 result = HMM_FastNormalize(v2);
+        EXPECT_NEAR(HMM_LengthVec2(result), 1.0f, 0.001f);
+        EXPECT_GT(result.X, 0.0f);
+        EXPECT_LT(result.Y, 0.0f);
+    }
+    {
+        hmm_vec3 result = HMM_FastNormalize(v3);
+        EXPECT_NEAR(HMM_LengthVec3(result), 1.0f, 0.001f);
+        EXPECT_GT(result.X, 0.0f);
+        EXPECT_LT(result.Y, 0.0f);
+        EXPECT_GT(result.Z, 0.0f);
+    }
+    {
+        hmm_vec4 result = HMM_FastNormalize(v4);
+        EXPECT_NEAR(HMM_LengthVec4(result), 1.0f, 0.001f);
+        EXPECT_GT(result.X, 0.0f);
+        EXPECT_LT(result.Y, 0.0f);
+        EXPECT_GT(result.Z, 0.0f);
+        EXPECT_LT(result.W, 0.0f);
+    }
+#endif
+}
+
+TEST(VectorOps, FastNormalizeZero)
+{
+    hmm_vec2 v2 = HMM_Vec2(0.0f, 0.0f);
+    hmm_vec3 v3 = HMM_Vec3(0.0f, 0.0f, 0.0f);
+    hmm_vec4 v4 = HMM_Vec4(0.0f, 0.0f, 0.0f, 0.0f);
+
+    {
+        hmm_vec2 result = HMM_FastNormalizeVec2(v2);
+        EXPECT_FLOAT_EQ(result.X, 0.0f);
+        EXPECT_FLOAT_EQ(result.Y, 0.0f);
+    }
+    {
+        hmm_vec3 result = HMM_FastNormalizeVec3(v3);
+        EXPECT_FLOAT_EQ(result.X, 0.0f);
+        EXPECT_FLOAT_EQ(result.Y, 0.0f);
+        EXPECT_FLOAT_EQ(result.Z, 0.0f);
+    }
+    {
+        hmm_vec4 result = HMM_FastNormalizeVec4(v4);
+        EXPECT_FLOAT_EQ(result.X, 0.0f);
+        EXPECT_FLOAT_EQ(result.Y, 0.0f);
+        EXPECT_FLOAT_EQ(result.Z, 0.0f);
+        EXPECT_FLOAT_EQ(result.W, 0.0f);
+    }
+
+#ifdef __cplusplus
+    {
+        hmm_vec2 result = HMM_FastNormalize(v2);
+        EXPECT_FLOAT_EQ(result.X, 0.0f);
+        EXPECT_FLOAT_EQ(result.Y, 0.0f);
+    }
+    {
+        hmm_vec3 result = HMM_FastNormalize(v3);
+        EXPECT_FLOAT_EQ(result.X, 0.0f);
+        EXPECT_FLOAT_EQ(result.Y, 0.0f);
+        EXPECT_FLOAT_EQ(result.Z, 0.0f);
+    }
+    {
+        hmm_vec4 result = HMM_FastNormalize(v4);
+        EXPECT_FLOAT_EQ(result.X, 0.0f);
+        EXPECT_FLOAT_EQ(result.Y, 0.0f);
+        EXPECT_FLOAT_EQ(result.Z, 0.0f);
+        EXPECT_FLOAT_EQ(result.W, 0.0f);
+    }
+#endif
+}
+
 TEST(VectorOps, Cross)
 {
     hmm_vec3 v1 = HMM_Vec3(1.0f, 2.0f, 3.0f);