fixed cos sin

Common/vec.h

@@ -20,6 +20,12 @@ typedef union {
   } s;
 } com_vec_t;
 
+static inline com_vec_t com_vec_identity(void) {
+  return (com_vec_t){.s = {.x = COM_FIXED_FRACUNIT,
+                           .y = COM_FIXED_FRACUNIT,
+                           .z = COM_FIXED_FRACUNIT}};
+}
+
 static inline com_vec_t com_vec_add(com_vec_t a, com_vec_t b) {
   return (com_vec_t){.s = {.x = com_fixed_add(a.s.x, b.s.x),
                            .y = com_fixed_add(a.s.y, b.s.y),