Vector3f: add some numeric operations

Vector3f.h

@@ -9,6 +9,32 @@ class Vector3f {
         return vals[offset];
     };
 
+    float operator [](size_t offset) const {
+        return vals[offset];
+    };
+
+    Vector3f operator +=(const Vector3f other) {
+        vals[0] += other[0];
+        vals[1] += other[1];
+        vals[2] += other[2];
+        return *this;
+    };
+
+    Vector3f operator /=(const uint64_t divisor) {
+        vals[0] /= (float)divisor;
+        vals[1] /= (float)divisor;
+        vals[2] /= (float)divisor;
+        return *this;
+    };
+
+    Vector3f operator -(const Vector3f other) {
+        Vector3f ret;
+        ret[0] = vals[0] - other[0];
+        ret[1] = vals[1] - other[1];
+        ret[2] = vals[2] - other[2];
+        return ret;
+    };
+
     double len() const {
         return sqrt(vals[0]*vals[0] + vals[1]*vals[1] + vals[2]*vals[2]);
     }