+ * -----------------------------------------------------------------------------
+ * Section 3 Quaternions
+ * -----------------------------------------------------------------------------
+ */
+
+static inline void q_identity( v4f q )
+{
+ q[0] = 0.0f; q[1] = 0.0f; q[2] = 0.0f; q[3] = 1.0f;
+}
+
+static inline void q_axis_angle( v4f q, v3f axis, f32 angle )
+{
+ f32 a = angle*0.5f,
+ c = cosf(a),
+ s = sinf(a);
+
+ q[0] = s*axis[0];
+ q[1] = s*axis[1];
+ q[2] = s*axis[2];
+ q[3] = c;
+}
+
+static inline void q_mul( v4f q, v4f q1, v4f d )
+{
+ v4f t;
+ t[0] = q[3]*q1[0] + q[0]*q1[3] + q[1]*q1[2] - q[2]*q1[1];
+ t[1] = q[3]*q1[1] - q[0]*q1[2] + q[1]*q1[3] + q[2]*q1[0];
+ t[2] = q[3]*q1[2] + q[0]*q1[1] - q[1]*q1[0] + q[2]*q1[3];
+ t[3] = q[3]*q1[3] - q[0]*q1[0] - q[1]*q1[1] - q[2]*q1[2];
+ v4_copy( t, d );
+}
+
+static inline void q_normalize( v4f q )
+{
+ f32 l2 = v4_dot(q,q);
+ if( l2 < 0.00001f ) q_identity( q );
+ else {
+ f32 s = 1.0f/sqrtf(l2);
+ q[0] *= s;
+ q[1] *= s;
+ q[2] *= s;
+ q[3] *= s;
+ }
+}
+
+static inline void q_inv( v4f q, v4f d )
+{
+ f32 s = 1.0f / v4_dot(q,q);
+ d[0] = -q[0]*s;
+ d[1] = -q[1]*s;
+ d[2] = -q[2]*s;
+ d[3] = q[3]*s;
+}
+
+static inline void q_nlerp( v4f a, v4f b, f32 t, v4f d ){
+ if( v4_dot(a,b) < 0.0f ){
+ v4f c;
+ v4_muls( b, -1.0f, c );
+ v4_lerp( a, c, t, d );
+ }
+ else
+ v4_lerp( a, b, t, d );
+
+ q_normalize( d );
+}
+
+static inline void q_m3x3( v4f q, m3x3f d )
+{
+ f32
+ l = v4_length(q),
+ s = l > 0.0f? 2.0f/l: 0.0f,
+
+ xx = s*q[0]*q[0], xy = s*q[0]*q[1], wx = s*q[3]*q[0],
+ yy = s*q[1]*q[1], yz = s*q[1]*q[2], wy = s*q[3]*q[1],
+ zz = s*q[2]*q[2], xz = s*q[0]*q[2], wz = s*q[3]*q[2];
+
+ d[0][0] = 1.0f - yy - zz;
+ d[1][1] = 1.0f - xx - zz;
+ d[2][2] = 1.0f - xx - yy;
+ d[0][1] = xy + wz;
+ d[1][2] = yz + wx;
+ d[2][0] = xz + wy;
+ d[1][0] = xy - wz;
+ d[2][1] = yz - wx;
+ d[0][2] = xz - wy;
+}
+
+static void q_mulv( v4f q, v3f v, v3f d )
+{
+ v3f v1, v2;
+
+ v3_muls( q, 2.0f*v3_dot(q,v), v1 );
+ v3_muls( v, q[3]*q[3] - v3_dot(q,q), v2 );
+ v3_add( v1, v2, v1 );
+ v3_cross( q, v, v2 );
+ v3_muls( v2, 2.0f*q[3], v2 );
+ v3_add( v1, v2, d );
+}
+
+static f32 q_dist( v4f q0, v4f q1 ){
+ return acosf( 2.0f * v4_dot(q0,q1) -1.0f );
+}
+
+/*
+ * -----------------------------------------------------------------------------
+ * Section 4.a 2x2 matrices
+ * -----------------------------------------------------------------------------