2 files changed, 15 insertions, 1 deletions
diff --git a/include/fml/quat.h b/include/fml/quat.h
index 14c966e..67a89d5 100644
--- a/include/fml/quat.h
+++ b/include/fml/quat.h
@@ -15,11 +15,15 @@ namespace fml {
         quat(vec3 vec);
         quat();
 
-        operator vec3();
+        operator vec3() const;
 
         quat conjugate() const;
 
+        /* returns <cos / 2, x * sin / 2, y * sin / 2, z * sin / 2> */
         static quat from_angleaxis(scalar angle, vec3 axis);
+
+        /* returns rotquat * this * rotquat.conj */
+        quat rotateby(const quat &rotquat) const;
     };
 
     quat operator*(const quat &, const quat &);
diff --git a/include/fml/vec3.h b/include/fml/vec3.h
index 3460c56..a006619 100644
--- a/include/fml/vec3.h
+++ b/include/fml/vec3.h
@@ -5,6 +5,8 @@
 #include "fml.h"
 
 namespace fml {
+    class quat;
+
     class vec3 {
     public:
         scalar v[3];
@@ -27,7 +29,15 @@ namespace fml {
         scalar magnitudeSquared() const;
         vec3 normalize() const;
         scalar dot(const vec3 &other) const;
+
+        /* order is this x other. */
         vec3 cross(const vec3 &other) const;
+
+        /* rotate by a rotation quaternion */
+        vec3 rotateby(const quat &rotquat) const;
+
+        /* return an arbitrary unit vector normal to other */
+        static vec3 any_unit_normal(const vec3 &other);
     };
 
     vec3 operator*(scalar scale, const vec3 &v);