mathbox_3d_require.clj

;; # Custom Viewers with d3-require
^{:nextjournal.clerk/visibility #{:hide-ns}}
(ns mathbox-d3-require
  (:require [nextjournal.clerk :as clerk]))

;; This is a custom viewer for a cube rendered
;; with [Mathbox](https://gitgud.io/unconed/mathbox). Note that Mathbox isn't
;; bundled with Clerk but we use a component based
;; on [d3-require](https://github.com/d3/d3-require) to load it at runtime.

(def mathbox-cube
  {:fetch-fn (fn [_ x] x)

   :render-fn
   ;; I was trying here to get some state where I could stash the mathbox
   ;; instance, so I could reset it below when the inputs changed.
   ;;
   ;; But it seems that Clerk only reuses the render function if the value
   ;; doesn't change. If it DOES change (the whole point of !ref) then the form
   ;; is re-evaluated and `!ref` is nil again.
   '(let [!ref (atom nil)]
      (fn [value]
        (v/html
         (when value
           [v/with-d3-require {:package ["[email protected]"]}
            (fn [three]
              (let [Color (.-Color three)]
                [v/with-d3-require
                 {:package ["[email protected]/build/mathbox-bundle.js"]}
                 (fn [mb]
                   (.log js/console "ref: " @!ref)
                   [:div {:id "mathbox"
                          :style {:height "400px" :width "100%"}
                          :ref
                          (fn [el]
                            (when el
                              ;; my attempt at caching a mathbox instance, and
                              ;; resetting it if the function is called a second
                              ;; time.
                              (swap! !ref (fn [box]
                                            (.log js/console box)
                                            (if box
                                              (do (.log js/console "removing")
                                                  (.remove box  "*")
                                                  box)
                                              (let [box ((.-mathBox mb)
                                                         (clj->js
                                                          {:plugins  ["core" "controls" "cursor"]
                                                           :controls {:klass (.-OrbitControls mb)}
                                                           :element el
                                                           :camera   {}}))]
                                                ;; some basic scene setup.
                                                (doto (.-three box)
                                                  (-> .-controls .-maxDistance (set! 4))
                                                  (-> .-camera .-position (.set 2.5 1 2.5))
                                                  (-> .-renderer (.setClearColor (Color. 0xeeeeee) 1.0)))
                                                box))))
                              (let [mathbox @!ref]
                                ;; generate a 3d cartesian plane...
                                (let [view
                                      (-> mathbox
                                          (.set (clj->js
                                                 {:scale 720
                                                  :focus 1}))
                                          (.cartesian
                                           (clj->js
                                            {:range [[0 1] [0 1] [0 1]]
                                             :scale [1 1 1]})))

                                      ;; and make this function for adding
                                      ;; a "volume", which is a 3d data grid you
                                      ;; can attach things to...
                                      add-volume!
                                      (fn [id {:keys [width-rez height-rez depth-rez
                                                     size
                                                     opacity]
                                              :or {width-rez 4 height-rez 4 depth-rez 4
                                                   size 30
                                                   opacity 1.0}
                                              :as m}
                                          size opacity]
                                        (doto view
                                          (.volume
                                           (clj->js
                                            {:id id
                                             :width width-rez
                                             :height height-rez
                                             :depth depth-rez
                                             :items 1,
                                             :channels 4
                                             :live false
                                             :expr (fn [emit x y z]
                                                     (emit x y z opacity))}))

                                          ;; internally a point is added to each
                                          ;; node in the volume.
                                          (.point
                                           (clj->js
                                            {;; The neat trick: use the same data
                                             ;; for position and for color! We
                                             ;; don't actually need to specify the
                                             ;; points source since we just
                                             ;; defined them but it emphasizes
                                             ;; what's going on.
                                             ;;
                                             ;; The w component 1 is ignored as a
                                             ;; position but used as opacity as a
                                             ;; color.
                                             :points (str "#" id)
                                             :colors (str "#" id)
                                             ;; Multiply every color component in [0..1] by 255
                                             :color 0xffffff
                                             :size size}))))]
                                  (add-volume! "volume" value)))))}])]))]))))})

;; We can then use  the above viewer using `with-viewer`:
(clerk/with-viewer mathbox-cube
  {:width-rez 2
   :height-rez 3
   :depth-rez 3
   :size 30
   :opacity 1.0})