From d8c6d4c19887eb1566c80cf7f0dac722d01b51d9 Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Tue, 7 May 2013 10:20:37 +0000
Subject: [PATCH] doc: add some comments in vector.cpp functions.
---
src/math/vector.cpp | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/src/math/vector.cpp b/src/math/vector.cpp
index fc356f64..d60d82ac 100644
--- a/src/math/vector.cpp
+++ b/src/math/vector.cpp
@@ -24,12 +24,18 @@ using namespace std;
namespace lol
{
+/*
+ * Return the determinant of a 2�2 matrix.
+ */
static inline float det2(float a, float b,
float c, float d)
{
return a * d - b * c;
}
+/*
+ * Return the determinant of a 3�3 matrix.
+ */
static inline float det3(float a, float b, float c,
float d, float e, float f,
float g, float h, float i)
@@ -39,11 +45,18 @@ static inline float det3(float a, float b, float c,
+ c * (d * h - g * e);
}
+/*
+ * Return the cofactor of the (i,j) entry in a 2�2 matrix.
+ */
static inline float cofact(mat2 const &mat, int i, int j)
{
- return mat[(i + 1) & 1][(j + 1) & 1] * (((i + j) & 1) ? -1.0f : 1.0f);
+ float tmp = mat[(i + 1) & 1][(j + 1) & 1];
+ return ((i + j) & 1) ? -tmp : tmp;
}
+/*
+ * Return the cofactor of the (i,j) entry in a 3�3 matrix.
+ */
static inline float cofact(mat3 const &mat, int i, int j)
{
return det2(mat[(i + 1) % 3][(j + 1) % 3],
@@ -52,6 +65,9 @@ static inline float cofact(mat3 const &mat, int i, int j)
mat[(i + 2) % 3][(j + 2) % 3]);
}
+/*
+ * Return the cofactor of the (i,j) entry in a 4�4 matrix.
+ */
static inline float cofact(mat4 const &mat, int i, int j)
{
return det3(mat[(i + 1) & 3][(j + 1) & 3],
@@ -67,7 +83,8 @@ static inline float cofact(mat4 const &mat, int i, int j)
template<> float determinant(mat2 const &mat)
{
- return mat[0][0] * mat[1][1] - mat[0][1] * mat[1][0];
+ return det2(mat[0][0], mat[0][1],
+ mat[1][0], mat[1][1]);
}
template<> mat2 transpose(mat2 const &mat)