Chapter 0 Example 7 Two-Dimensional Noise

notebooks/chapter_0.md

@@ -206,3 +206,22 @@ around the edges, so I implemented movement wrapping so the paths generated by
 the perlin noise are more apparent.
 
 Toggle between movement wrapping and canvas-constrained movement by clicking the checkbox.
+
+## [Example: Two-Dimensional Noise](https://natureofcode.com/random/#two-dimensional-noise)
+
+
+```clojure
+^{::clerk/no-cache true ::clerk/viewer clerk/code}
+(slurp "src/noc/chapter_0_7.cljs")
+(show-sketch :c0.7)
+```
+
+This example doesn't have a number, but I thought I'd include it anyways. The
+original JS implementation used a nested for loop that mutates the loop variable
+on each iteration.
+
+Of course in clojure we can't do that [^um-actually], so I took the approach of pre-computing the `xoffs` and `yoffs` as a lazy sequence.
+
+Click that reset button to see it regenerated!
+
+[^um-actually]: Well, technically we can using dynamic vars or an atom, but that's pretty nasty and should only be used as an escape hatch when necessary.

src/noc/chapter_0_7.cljs

@@ -0,0 +1,26 @@
+(ns noc.chapter-0-7
+  (:require
+   [quil.core :as q]))
+
+(def size [640 240])
+
+(defn init-state [_]
+  {})
+
+(defn setup! [{:keys [width height]}]
+  (q/noise-seed (rand-int (-> js/Number (.-MAX_SAFE_INTEGER))))
+  (q/background 255)
+  (let [img  (q/create-image width height)
+        xoffs (take width (iterate #(+ % 0.01) 0.0))]
+    (doseq [[x xoff] (map-indexed vector xoffs)]
+      (let [yoffs (take height (iterate #(+ % 0.01) 0.0))]
+        (doseq [[y yoff] (map-indexed vector yoffs)]
+          (let [bright (Math/floor (q/map-range (q/noise xoff yoff) 0 1 0 255))]
+            (q/set-pixel img x y bright)))))
+    (q/update-pixels img)
+    (q/image img 0 0)))
+
+(defn tick [state]
+  state)
+
+(defn draw! [_])

src/noc/sketch.cljs

@@ -14,7 +14,8 @@
             [noc.chapter-0-5 :as c0.5]
             [noc.chapter-0-6e :as c0.6e]
             [noc.chapter-0-6 :as c0.6]
-            [noc.chapter-0-7e :as c0.7e]))
+            [noc.chapter-0-7e :as c0.7e]
+            [noc.chapter-0-7 :as c0.7]))
 
 (def sketches {:walker (sketch-> c0.1)
                :rand-dist (sketch-> c0.2)
@@ -26,7 +27,8 @@
                :c0.5 (sketch-> c0.5)
                :c0.6e (sketch-> c0.6e)
                :c0.6 (sketch-> c0.6)
-               :c0.7e (sketch-> c0.7e)})
+               :c0.7e (sketch-> c0.7e)
+               :c0.7 (sketch-> c0.7)})
 
 (defn load-sketch [s]
   (when-let [sk (get sketches s)]
@@ -78,7 +80,8 @@
 (defn setup-state [init-fn]
   (-> (default-state (time-now!))
       (merge (init-fn {:width (q/width) :height (q/height)}))
-      (ui/prepare-ui)))
+      (ui/prepare-ui)
+      (assoc :width (q/width) :height (q/height))))
 
 (defn reset [sketch*]
   (let [{:keys [applet opts]} @sketch*
@@ -87,7 +90,7 @@
       (let [state* (q/state-atom)]
         (ui/remove-all! @state*)
         (reset! state* (setup-state init))
-        (setup)))))
+        (setup @state*)))))
 
 (defn pause [sketch*]
   (let [{:keys [applet]} @sketch*]