(defn attrib-buffer-view
  [ptr stride num]
  (js/Float32Array. (.-buffer (aget js/Particles "HEAPU8")) ptr (* stride num)))

(defn update-attrib-buffer
  [gl attrib ptr stride num]
  (.bindBuffer gl glc/array-buffer
               (get-in (:scene @app) [:particles :attribs attrib :buffer]))
  (.bufferData gl glc/array-buffer
               (attrib-buffer-view ptr stride num)
               glc/dynamic-draw))

(defn update
  []
  (let [{:keys [gl psys psys-update psys-count particle-ptr scene mpos]} @app]
    (psys-update psys)
    (update-attrib-buffer gl :position particle-ptr 9 10000)
    (update-attrib-buffer gl :color (+ particle-ptr 24) 9 10000)
    (doto gl
      (gl/clear-color-and-depth-buffer (col/rgba 0 0 0.1) 1)
      (gl/draw-with-shader
       (-> (:particles scene)
           (assoc :num-vertices (psys-count psys))
           (assoc-in [:uniforms :model]
                     (-> M44
                         (g/rotate-x (* (mpos 1) 0.001))
                         (g/rotate-y (* (mpos 0) 0.001))
                         (g/scale 0.1))))))))