From e1d0beae1a7d5f287c7f41d34e291a7737de1576 Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Tue, 8 May 2012 11:56:39 +0000
Subject: [PATCH] math: support all Tait-Bryan angle combinations in
 quaternions.

---
 src/lol/math/vector.h | 23 +++++++++++--
 src/math/vector.cpp   | 80 +++++++++++++++++++++++++++++++++++++------
 2 files changed, 91 insertions(+), 12 deletions(-)

diff --git a/src/lol/math/vector.h b/src/lol/math/vector.h
index 143c26dc..008ebb92 100644
--- a/src/lol/math/vector.h
+++ b/src/lol/math/vector.h
@@ -925,8 +925,27 @@ template <typename T> struct Quat
 
     static Quat<T> rotate(T angle, T x, T y, T z);
     static Quat<T> rotate(T angle, Vec3<T> const &v);
-    static Quat<T> fromeuler(T x, T y, T z);
-    static Quat<T> fromeuler(Vec3<T> const &v);
+
+    /* Convert from Tait-Bryan angles (incorrectly called Euler angles,
+     * but since everyone does it…). The axes in fromeuler_xyz are
+     * x, then y', then z", ie. the axes are attached to the model.
+     * If you want to apply yaw around x, pitch around y, and roll
+     * around z, use fromeuler_xyz.
+     * If you want to rotate around static axes, reverse the order in
+     * the function name (_zyx instead of _xyz) AND reverse the order
+     * of the arguments. */
+    static Quat<T> fromeuler_xyz(Vec3<T> const &v);
+    static Quat<T> fromeuler_xzy(Vec3<T> const &v);
+    static Quat<T> fromeuler_yxz(Vec3<T> const &v);
+    static Quat<T> fromeuler_yzx(Vec3<T> const &v);
+    static Quat<T> fromeuler_zxy(Vec3<T> const &v);
+    static Quat<T> fromeuler_zyx(Vec3<T> const &v);
+    static Quat<T> fromeuler_xyz(T phi, T theta, T psi);
+    static Quat<T> fromeuler_xzy(T phi, T theta, T psi);
+    static Quat<T> fromeuler_yxz(T phi, T theta, T psi);
+    static Quat<T> fromeuler_yzx(T phi, T theta, T psi);
+    static Quat<T> fromeuler_zxy(T phi, T theta, T psi);
+    static Quat<T> fromeuler_zyx(T phi, T theta, T psi);
 
     inline Quat<T> operator *(Quat<T> const &val) const
     {
diff --git a/src/math/vector.cpp b/src/math/vector.cpp
index 58525c9e..13b9904b 100644
--- a/src/math/vector.cpp
+++ b/src/math/vector.cpp
@@ -538,25 +538,85 @@ template<> mat3 mat3::fromeuler(float x, float y, float z)
     return mat3::fromeuler(vec3(x, y, z));
 }
 
-template<> quat quat::fromeuler(vec3 const &v)
+static inline quat fromeuler_generic(vec3 const &v, int s, int i, int j, int k)
 {
     using std::sin;
     using std::cos;
 
     vec3 half_angles = (M_PI / 360.0f) * v;
-    float sx = sin(half_angles.x), cx = cos(half_angles.x);
-    float sy = sin(half_angles.y), cy = cos(half_angles.y);
-    float sz = sin(half_angles.z), cz = cos(half_angles.z);
+    float s0 = sin(half_angles[0]), c0 = cos(half_angles[0]);
+    float s1 = sin(half_angles[1]), c1 = cos(half_angles[1]);
+    float s2 = sin(half_angles[2]), c2 = cos(half_angles[2]);
 
-    return quat(cx * cy * cz + sx * sy * sz,
-                sx * cy * cz - cx * sy * sz,
-                cx * sy * cz + sx * cy * sz,
-                cx * cy * sz - sx * sy * cz);
+    vec4 v1(c0 * c1 * c2,  c0 * c1 * s2, c0 * s1 * c2,  s0 * c1 * c2);
+    vec4 v2(s0 * s1 * s2, -s0 * s1 * c2, s0 * c1 * s2, -c0 * s1 * s2);
+
+    if (s > 0)
+        v1 += v2;
+    else
+        v1 -= v2;
+
+    return quat(v1[0], v1[i], v1[j], v1[k]);
+}
+
+template<> quat quat::fromeuler_xyz(vec3 const &v)
+{
+    return fromeuler_generic(v, -1, 3, 2, 1);
+}
+
+template<> quat quat::fromeuler_xzy(vec3 const &v)
+{
+    return fromeuler_generic(v, 1, 3, 1, 2);
+}
+
+template<> quat quat::fromeuler_yxz(vec3 const &v)
+{
+    return fromeuler_generic(v, 1, 2, 3, 1);
+}
+
+template<> quat quat::fromeuler_yzx(vec3 const &v)
+{
+    return fromeuler_generic(v, -1, 1, 3, 2);
+}
+
+template<> quat quat::fromeuler_zxy(vec3 const &v)
+{
+    return fromeuler_generic(v, -1, 2, 1, 3);
+}
+
+template<> quat quat::fromeuler_zyx(vec3 const &v)
+{
+    return fromeuler_generic(v, 1, 1, 2, 3);
+}
+
+template<> quat quat::fromeuler_xyz(float phi, float theta, float psi)
+{
+    return quat::fromeuler_zyx(vec3(phi, theta, psi));
+}
+
+template<> quat quat::fromeuler_xzy(float phi, float theta, float psi)
+{
+    return quat::fromeuler_yxz(vec3(phi, theta, psi));
+}
+
+template<> quat quat::fromeuler_yxz(float phi, float theta, float psi)
+{
+    return quat::fromeuler_yxz(vec3(phi, theta, psi));
+}
+
+template<> quat quat::fromeuler_yzx(float phi, float theta, float psi)
+{
+    return quat::fromeuler_yxz(vec3(phi, theta, psi));
+}
+
+template<> quat quat::fromeuler_zxy(float phi, float theta, float psi)
+{
+    return quat::fromeuler_yxz(vec3(phi, theta, psi));
 }
 
-template<> quat quat::fromeuler(float x, float y, float z)
+template<> quat quat::fromeuler_zyx(float phi, float theta, float psi)
 {
-    return quat::fromeuler(vec3(x, y, z));
+    return quat::fromeuler_yxz(vec3(phi, theta, psi));
 }
 
 template<> mat4 mat4::lookat(vec3 eye, vec3 center, vec3 up)