From bcf7937eec0c182cdd781e4b93a49dd5ba5c8746 Mon Sep 17 00:00:00 2001
From: Ben Visness <bvisness@gmail.com>
Date: Thu, 25 Aug 2016 14:08:46 -0500
Subject: [PATCH] Ensure column-major order for matrices and fix HMM_Translate

Most of the changes in this patch are cosmetic (such as looping by
columns first.) HMM_Translate was incorrectly producing row-major
matrices, which should now be fixed.

Fixes #22
---
 HandmadeMath.h | 77 +++++++++++++++++++++++---------------------------
 1 file changed, 35 insertions(+), 42 deletions(-)

diff --git a/HandmadeMath.h b/HandmadeMath.h
index 860bea6..33ed44e 100644
--- a/HandmadeMath.h
+++ b/HandmadeMath.h
@@ -1,5 +1,5 @@
 /*
-  HandmadeMath.h v0.5
+  HandmadeMath.h v0.5.1
 
   This is a single header file with a bunch of useful functions for
   basic game math operations.
@@ -116,6 +116,9 @@
           (*) 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
 
 
 
@@ -987,16 +990,6 @@ HMM_Mat4d(float Diagonal)
 {
     hmm_mat4 Result = HMM_Mat4();
 
-    int Rows;
-    for(Rows = 0; Rows < 4; ++Rows)
-    {
-        int Columns;
-        for(Columns = 0; Columns < 4; ++Columns)
-        {
-            Result.Elements[Rows][Columns] = 0.0f;
-        }
-    }
-
     Result.Elements[0][0] = Diagonal;
     Result.Elements[1][1] = Diagonal;
     Result.Elements[2][2] = Diagonal;
@@ -1010,13 +1003,13 @@ HMM_AddMat4(hmm_mat4 Left, hmm_mat4 Right)
 {
     hmm_mat4 Result = HMM_Mat4();
 
-    int Rows;
-    for (Rows = 0; Rows < 4; ++Rows)
+    int Columns;
+    for(Columns = 0; Columns < 4; ++Columns)
     {
-        int Columns;
-        for (Columns = 0; Columns < 4; ++Columns)
+        int Rows;
+        for(Rows = 0; Rows < 4; ++Rows)
         {
-            Result.Elements[Rows][Columns] = Left.Elements[Rows][Columns] + Right.Elements[Rows][Columns];
+            Result.Elements[Columns][Rows] = Left.Elements[Columns][Rows] + Right.Elements[Columns][Rows];
         }
     }
 
@@ -1028,13 +1021,13 @@ HMM_SubtractMat4(hmm_mat4 Left, hmm_mat4 Right)
 {
     hmm_mat4 Result = HMM_Mat4();
 
-    int Rows;
-    for (Rows = 0; Rows < 4; ++Rows)
+    int Columns;
+    for(Columns = 0; Columns < 4; ++Columns)
     {
-        int Columns;
-        for (Columns = 0; Columns < 4; ++Columns)
+        int Rows;
+        for(Rows = 0; Rows < 4; ++Rows)
         {
-            Result.Elements[Rows][Columns] = Left.Elements[Rows][Columns] - Right.Elements[Rows][Columns];
+            Result.Elements[Columns][Rows] = Left.Elements[Columns][Rows] - Right.Elements[Columns][Rows];
         }
     }
 
@@ -1046,20 +1039,20 @@ HMM_MultiplyMat4(hmm_mat4 Left, hmm_mat4 Right)
 {
     hmm_mat4 Result = HMM_Mat4();
 
-    int Rows;
-    for(Rows = 0; Rows < 4; ++Rows)
+    int Columns;
+    for(Columns = 0; Columns < 4; ++Columns)
     {
-        int Columns;
-        for(Columns = 0; Columns < 4; ++Columns)
+        int Rows;
+        for(Rows = 0; Rows < 4; ++Rows)
         {
             float Sum = 0;
             int CurrentMatrice;
             for(CurrentMatrice = 0; CurrentMatrice < 4; ++CurrentMatrice)
             {
-                Sum += Right.Elements[Rows][CurrentMatrice] * Left.Elements[CurrentMatrice][Columns];
+                Sum += Left.Elements[CurrentMatrice][Rows] * Right.Elements[Columns][CurrentMatrice];
             }
 
-            Result.Elements[Rows][Columns] = Sum;
+            Result.Elements[Columns][Rows] = Sum;
         }
     }
 
@@ -1071,13 +1064,13 @@ HMM_MultiplyMat4f(hmm_mat4 Matrix, float Scalar)
 {
     hmm_mat4 Result = HMM_Mat4();
 
-    int Rows;
-    for (Rows = 0; Rows < 4; ++Rows)
+    int Columns;
+    for(Columns = 0; Columns < 4; ++Columns)
     {
-        int Columns;
-        for (Columns = 0; Columns < 4; ++Columns)
+        int Rows;
+        for(Rows = 0; Rows < 4; ++Rows)
         {
-            Result.Elements[Rows][Columns] = Matrix.Elements[Rows][Columns] * Scalar;
+            Result.Elements[Columns][Rows] = Matrix.Elements[Columns][Rows] * Scalar;
         }
     }
 
@@ -1089,13 +1082,13 @@ HMM_MultiplyMat4ByVec4(hmm_mat4 Matrix, hmm_vec4 Vector)
 {
     hmm_vec4 Result = {0};
     
-    int Rows, Columns;
+    int Columns, Rows;
     for(Rows = 0; Rows < 4; ++Rows)
     {
         float Sum = 0;
         for(Columns = 0; Columns < 4; ++Columns)
         {
-            Sum += Matrix.Elements[Rows][Columns] * Vector.Elements[Columns];
+            Sum += Matrix.Elements[Columns][Rows] * Vector.Elements[Columns];
         }
         
         Result.Elements[Rows] = Sum;
@@ -1109,13 +1102,13 @@ HMM_DivideMat4f(hmm_mat4 Matrix, float Scalar)
 {
     hmm_mat4 Result = HMM_Mat4();
 
-    int Rows;
-    for (Rows = 0; Rows < 4; ++Rows)
+    int Columns;
+    for(Columns = 0; Columns < 4; ++Columns)
     {
-        int Columns;
-        for (Columns = 0; Columns < 4; ++Columns)
+        int Rows;
+        for(Rows = 0; Rows < 4; ++Rows)
         {
-            Result.Elements[Rows][Columns] = Matrix.Elements[Rows][Columns] / Scalar;
+            Result.Elements[Columns][Rows] = Matrix.Elements[Columns][Rows] / Scalar;
         }
     }
 
@@ -1160,9 +1153,9 @@ HMM_Translate(hmm_vec3 Translation)
 {
     hmm_mat4 Result = HMM_Mat4d(1.0f);
 
-    Result.Elements[0][3] = Translation.X;
-    Result.Elements[1][3] = Translation.Y;
-    Result.Elements[2][3] = Translation.Z;
+    Result.Elements[3][0] = Translation.X;
+    Result.Elements[3][1] = Translation.Y;
+    Result.Elements[3][2] = Translation.Z;
 
     return (Result);
 }