Chapter 0 Example 6 and Exercise 7

notebooks/chapter_0.md

@@ -182,3 +182,27 @@ of being less than $r2$, thus more likely to be selected.
 (slurp "src/noc/chapter_0_6e.cljs")
 (show-sketch :c0.6e)
 ```
+
+
+## [Example 0.6: A Perlin Noise Walker](https://natureofcode.com/random/#example-06-a-perlin-noise-walker)
+
+```clojure
+^{::clerk/no-cache true ::clerk/viewer clerk/code}
+(slurp "src/noc/chapter_0_6.cljs")
+(show-sketch :c0.6)
+```
+
+
+## [Exercise 0.7: A Perlin Noise Walker - Step Size](https://natureofcode.com/random/#exercise-07)
+
+```clojure
+^{::clerk/no-cache true ::clerk/viewer clerk/code}
+(slurp "src/noc/chapter_0_7e.cljs")
+(show-sketch :c0.7e)
+```
+
+This one is rather different than the others. It spends a lot of time hovering
+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.

src/noc/chapter_0_6.cljs

@@ -0,0 +1,32 @@
+(ns noc.chapter-0-6
+  (:require
+   [goog.string :as gstring]
+   [goog.string.format]
+   [quil.core :as q]))
+
+(def size [640 240])
+
+(defn init-state [{:keys [width height]}]
+  {:walker {:x nil
+            :y nil
+            :tx 0
+            :ty 10000}})
+
+(defn setup! [_]
+  (q/background 255))
+
+(defn step-walker [width height {:keys [tx ty] :as walker}]
+  {:x (q/map-range (q/noise tx) 0 1 0 width)
+   :y (q/map-range (q/noise ty) 0 1 0 height)
+   :tx (+ tx 0.01)
+   :ty (+ ty 0.01)})
+
+(defn tick [{:keys [width height] :as state}]
+  (update state :walker (partial step-walker width height)))
+
+(defn draw! [{:keys [walker ui]}]
+  (q/stroke-weight 2)
+  (q/fill 127)
+  (q/stroke 0)
+  (when (:x walker)
+    (q/ellipse (:x walker) (:y walker) 48 48)))

src/noc/chapter_0_7e.cljs

@@ -0,0 +1,53 @@
+(ns noc.chapter-0-7e
+  (:require
+   [goog.string :as gstring]
+   [goog.string.format]
+   [quil.core :as q]))
+
+(def size [640 240])
+
+(defn init-state [{:keys [width height]}]
+  {:walker {:x (quot width 2)
+            :y (quot height 2)
+            :tx 0
+            :ty 10000}
+   :ui {:wrap {:type :checkbox :checked? true :label " Wrap Movement?"}}})
+
+(defn setup! [_]
+  (q/background 255))
+
+(defn tick [{:keys [width height ui] :as state}]
+  (letfn [(step-walker [{:keys [x y tx ty]}]
+            (let [max-step 10
+                  stepx (q/map-range (q/noise tx) 0 1 (- max-step) max-step)
+                  stepy (q/map-range (q/noise ty) 0 1 (- max-step) max-step)]
+              {:x (+ x stepx)
+               :y (+ y stepy)
+               :tx (+ tx 0.01)
+               :ty (+ ty 0.01)}))
+          (wrap [walker]
+            (-> walker
+                (update :x #(cond
+                              (>= % width) 0
+                              (< % 0) width
+                              :else %))
+                (update :y #(cond
+                              (>= % height) 0
+                              (< % 0) height
+                              :else %))))
+
+          (constrain [walker]
+            (-> walker
+                (update :x #(q/constrain % 0 (- width 1)))
+                (update :y #(q/constrain % 0 (- height 1)))))]
+    (update state :walker (comp
+                           (if (get-in ui [:wrap :checked?])
+                             wrap
+                             constrain) step-walker))))
+
+(defn draw! [{:keys [walker ui]}]
+  (q/stroke-weight 2)
+  (q/fill 127)
+  (q/stroke 0)
+  (when (:x walker)
+    (q/ellipse (:x walker) (:y walker) 48 48)))

src/noc/sketch.cljs

@@ -12,7 +12,9 @@
             [noc.chapter-0-4e :as c0.4e]
             [noc.chapter-0-5e :as c0.5e]
             [noc.chapter-0-5 :as c0.5]
-            [noc.chapter-0-6e :as c0.6e]))
+            [noc.chapter-0-6e :as c0.6e]
+            [noc.chapter-0-6 :as c0.6]
+            [noc.chapter-0-7e :as c0.7e]))
 
 (def sketches {:walker (sketch-> c0.1)
                :rand-dist (sketch-> c0.2)
@@ -22,7 +24,9 @@
                :c0.4e (sketch-> c0.4e)
                :c0.5e (sketch-> c0.5e)
                :c0.5 (sketch-> c0.5)
-               :c0.6e (sketch-> c0.6e)})
+               :c0.6e (sketch-> c0.6e)
+               :c0.6 (sketch-> c0.6)
+               :c0.7e (sketch-> c0.7e)})
 
 (defn load-sketch [s]
   (when-let [sk (get sketches s)]