math: add outer product for matrices and vectors.

src/lol/math/matrix.h

@@ -548,6 +548,37 @@ static inline mat_t<T, N, N> &operator *=(mat_t<T, N, N> &a,
     return a = a * b;
 }
 
+/*
+ * Matrix-matrix outer product (Kronecker product)
+ */
+
+template<typename T, int COLS1, int COLS2, int ROWS1, int ROWS2>
+static inline mat_t<T, COLS1 * COLS2, ROWS1 * ROWS2>
+outer(mat_t<T, COLS1, ROWS1> const &a, mat_t<T, COLS2, ROWS2> const &b)
+{
+    /* FIXME: could this be optimised somehow? */
+    mat_t<T, COLS1 * COLS2, ROWS1 * ROWS2> ret;
+    for (int i1 = 0; i1 < COLS1; ++i1)
+        for (int j1 = 0; j1 < ROWS1; ++j1)
+            for (int i2 = 0; i2 < COLS2; ++i2)
+                for (int j2 = 0; j2 < ROWS2; ++j2)
+                    ret[i1 * COLS2 + i2][j1 * ROWS2 + j2]
+                        = a[i1][j1] * b[i2][j2];
+    return ret;
+}
+
+/*
+ * Vector-vector outer product
+ */
+
+template<typename T, int COLS, int ROWS>
+static inline mat_t<T, COLS, ROWS> outer(vec_t<T, ROWS> const &a,
+                                         vec_t<T, COLS> const &b)
+{
+    return *reinterpret_cast<mat_t<T, 1, ROWS> const *>(&a)
+         * *reinterpret_cast<mat_t<T, COLS, 1> const *>(&b);
+}
+
 #if !LOL_FEATURE_CXX11_CONSTEXPR
 #undef constexpr
 #endif

src/math/matrix.cpp

@@ -17,17 +17,6 @@
 namespace lol
 {
 
-template<> mat3 mat3::scale(float x)
-{
-    mat3 ret(1.0f);
-
-    ret[0][0] = x;
-    ret[1][1] = x;
-    ret[2][2] = x;
-
-    return ret;
-}
-
 template<> mat3 mat3::scale(float x, float y, float z)
 {
     mat3 ret(1.0f);
@@ -39,6 +28,11 @@ template<> mat3 mat3::scale(float x, float y, float z)
     return ret;
 }
 
+template<> mat3 mat3::scale(float x)
+{
+    return scale(x, x, x);
+}
+
 template<> mat3 mat3::scale(vec3 v)
 {
     return scale(v.x, v.y, v.z);
@@ -198,7 +192,10 @@ template<> mat4 mat4::frustum(float left, float right, float bottom,
     return ret;
 }
 
-//Returns a standard perspective matrix
+/*
+ * Return a standard perspective matrix
+ */
+
 template<> mat4 mat4::perspective(float fov_y, float width,
                                   float height, float near, float far)
 {
@@ -208,9 +205,14 @@ template<> mat4 mat4::perspective(float fov_y, float width,
     return frustum(-near * t1, near * t1, -near * t2, near * t2, near, far);
 }
 
-//Returns a perspective matrix with the camera location shifted to be on the near plane
+/*
+ * Return a perspective matrix with the camera location shifted to be on
+ * the near plane
+ */
+
 template<> mat4 mat4::shifted_perspective(float fov_y, float screen_size,
-                                          float screen_ratio_yx, float near, float far)
+                                          float screen_ratio_yx,
+                                          float near, float far)
 {
     float tan_y = tanf(radians(fov_y) * .5f);
     ASSERT(tan_y > 0.000001f);