Wind first pass

scratches/bootstrap.clj

@@ -8,12 +8,10 @@
 
 (def revenge (ref {:position [0. 0.]
                    :name "Revenge"
-                   :heading (normalize [1.0 1.0])
+                   :heading (normalize [0. 1.0])
                    :slots [{:type :downwind-sail :length 2 :furl 1.0}]
                    :velocity [1. 0.]}))
 
 (reset! ships [virginia-woolfe revenge])
 
 (show-ui)
-
-@tracked-ship

src/age_of_sail/core.clj

@@ -4,8 +4,19 @@
             [seesaw.core :refer :all]
             [seesaw.bind :as b])
   (:import com.formdev.flatlaf.FlatDarculaLaf))
-
-(def hardcoded-wind [0.1 3.0]) ;; A strong easternly wind!
+;; Wind
+(def hardcoded-winds '({:strength [0.1 3.0] :position [0. 0.]})) ;; A strong easternly wind!
+(defn sum-wind
+  "Wind at x is the sum of each wind force divided by its distance away" 
+  [x winds]
+  (reduce (fn [sum wind]
+            (let [dist (len (sub x (:position wind)))]
+              (if (> dist 1.0)
+                (add sum (scale (:strength wind) (/ (len (sub x (:position wind))))))
+                (add sum (:strength wind)))))
+          (zero)
+          winds))
+;; Ships
 (defonce ships (atom []))
 
 (defn ship-names
@@ -35,19 +46,20 @@
       force)))
 
 (defn physics-step
-  [ship wind]
+  [ship winds]
   (dosync
-   ;; Update position
-   (alter ship update :position add (scale (:velocity @ship) (/ tickrate)))
-   ;; linear dampening
-   (alter ship update :velocity scale (- 1.0 (/ 0.5 tickrate)))
-   ;; wind force
-   (alter ship update :velocity add (scale (downwind-sails-force @ship wind) (/ tickrate)))))
+   (let [wind (sum-wind (:position @ship) winds)]
+     ;; Update position
+     (alter ship update :position add (scale (:velocity @ship) (/ tickrate)))
+     ;; linear dampening
+     (alter ship update :velocity scale (- 1.0 (/ 0.5 tickrate)))
+     ;; wind force
+     (alter ship update :velocity add (scale (downwind-sails-force @ship wind) (/ tickrate))))))
 
 (defn tick
   [ships]
   (doseq [ship ships]
-    (-> ship (physics-step hardcoded-wind))))
+    (-> ship (physics-step hardcoded-winds))))
 
 (subscribe! #(tick @ships))
 

src/age_of_sail/vec2.clj

@@ -9,6 +9,10 @@
   [v1 v2]
   (mapv + v1 v2))
 
+(defn sub
+  [v1 v2]
+  (mapv - v1 v2))
+
 (defn scale
   [v & scalars]
   (mapv #(* (apply * scalars) %) v))