;;-*-Lisp-*-
(in-package goal)

;; name: quaternion-h.gc
;; name in dgo: quaternion-h
;; dgos: GAME, ENGINE

;; general quaternion type used to represent an orientation in a way that's compact (4 floats),
;; avoids singularities of euler angles, and reasonably efficient to transform.
;; the w component is stored last.
(deftype quaternion (structure)
  ((x    float           :offset-assert 0)
   (y    float           :offset-assert 4)
   (z    float           :offset-assert 8)
   (w    float           :offset-assert 12)
   (data float 4 :score -9999 :offset 0)
   (vec  vector  :inline :offset 0)
   (quad uint128         :offset 0)
   )
  :method-count-assert 9
  :size-assert         #x10
  :flag-assert         #x900000010
  )

(define *unity-quaternion* (new 'static 'quaternion :x 0.0 :y 0.0 :z 0.0 :w 1.0))

(define-extern matrix->quaternion (function quaternion matrix quaternion))
(define-extern vector-y-angle (function vector float))

(defmacro new-stack-quaternion0 ()
  "Get a stack quaternion that's set to 0.
   This is more efficient than (new 'stack 'quaternion) because
   this doesn't call the constructor."
  `(let ((q (new 'stack-no-clear 'quaternion)))
     (set! (-> q quad) (the-as uint128 0))
     q
     )
  )