Metaballs examples

metaballs.clj

(ns metaballs
  (:import
    [javax.swing JFrame]
    [java.awt Canvas Graphics Color]
    java.awt.image.BufferStrategy))

(set! *warn-on-reflection* true)

(def  SIZE 250)

;START:direction-and-position
;;reverse direction if we hit the edge of the screen
(defn direction [p v]
  (if (or (> p SIZE) (neg? p)) (- v) v))

;;compute the position and velocity of the ball
(defn move [{:keys [x y vx vy] :as ball}]
  (let [vx (direction x vx)
        vy (direction y vy)]
    (assoc ball :x (+ x vx) :y (+ y vy) :vx vx :vy vy)))
;END:direction-and-position

;START:color
(defn color-in-range [c]
  (int (if (< c 0) 0 (if (> c 255) 255 c))))

(defn color [r g b]
  (Color. (color-in-range r) (color-in-range g) (color-in-range b)))
;END:color

;START:influence-and-color
;;compute influence of each metaball
(defn influence [{:keys [x y radius]} px py]
  (let [dx (- x px)
        dy (- y py)]
    (/ radius (Math/sqrt (+ (* dx dx) (* dy dy))))))

;;compute the resulting RGB values based on influence
(defn compute-color [x y rgb ball]
  (let [influence (influence ball x y)
        [r g b] (:color ball)]
    (map #(+ %1 (* influence %2)) rgb (:color ball))))
;END:influence-and-color

(defn paint-square [g [red green blue] x y size]
  (doto g
    (.setColor (color red green blue))
    (.fillRect x y size size)))

(defn draw [canvas balls]
  (let [buffer (.getBufferStrategy canvas)
        g      (.getDrawGraphics buffer)
        step   2]
    (try
      (loop [x 0]
        (loop [y 0]
          (paint-square g
                        ;START:compute-colors
                        ;;for each x,y coordinate compute the color
                        (reduce (partial compute-color x y) [0 0 0] balls)
                        ;END:compute-colors
                        x y step)
          (if (< y (- SIZE step)) (recur (+ y step))))
        (if (< x (- SIZE step)) (recur (+ x step))))

      (finally (.dispose g)))
    (if-not (.contentsLost buffer)
      (.show buffer)) ))

(defn metaball []
  {:x      (rand-int SIZE)
   :y      (rand-int SIZE)
   :vx     (inc (rand-int 6))
   :vy     (inc (rand-int 6))
   :radius (+ 40 (rand-int 15))
   :color  (repeatedly 3 #(rand-int 256))})

(defn start [& [num-balls]]
  (let [frame  (JFrame. "Metaballs")
        canvas (Canvas.)]
    (doto frame
      (.setSize SIZE SIZE)
      (.setDefaultCloseOperation JFrame/EXIT_ON_CLOSE)
      (.setResizable false)
      (.add canvas)
      (.setVisible true))

    (doto canvas
      (.createBufferStrategy 2)
      (.setVisible true)
      (.requestFocus))

    ;START:main-loop
    ;;run this in a loop where we move the
    ;;balls around and render them
    (loop [balls (repeatedly (or num-balls 2) metaball)]
      (draw canvas balls)
      (recur (map move balls)))
    ;END:main-loop
    ))

metaballs_optimized.clj

(ns metaballs-optimized
  (:import
    [javax.swing JFrame]
    [java.awt Canvas Graphics Color]
    java.awt.image.BufferStrategy))

(set! *warn-on-reflection* true)
(def  SIZE 250)

;START:direction-and-position
;;reverse direction if we hit the edge of the screen
(defn direction [p v]
  (if (or (> p SIZE) (neg? p)) (- v) v))

;;compute the position and velocity of the ball
(defn move [{:keys [x y vx vy] :as ball}]
  (let [vx (direction x vx)
        vy (direction y vy)]
    (assoc ball :x (+ x vx) :y (+ y vy) :vx vx :vy vy)))
;END:direction-and-position

;START:color
(defn color-in-range [c]
  (if (< c 0) 0 (if (> c 255) 255 c)))

(defn color [[r g b]]
  (Color. ^int (color-in-range r)
          ^int (color-in-range r)
          ^int (color-in-range r)))
;END:color

;START:influence-and-color
;;compute influence of each metaball
(defn influence [{:keys [x y radius]} px py]
  (let [dx (double (- x px))
        dy (double (- y py))]
    (double (/ radius (Math/sqrt (+ (* dx dx) (* dy dy)))))))

;;compute the resulting RGB values based on influence
(defn compute-color [x y rgb ball]
  (let [influence (influence ball x y)
        [r g b] (:color ball)]
    (map #(+ %1 (* influence %2)) rgb (:color ball))))
;END:influence-and-color

(defn paint-square [^Graphics g rgb x y size]
  (doto g
    (.setColor ^Color (color rgb))
    (.fillRect x y size size)))

(defn draw [canvas balls]
  (let [buffer (.getBufferStrategy canvas)
        g      (.getDrawGraphics buffer)
        step   2]
    (try
      (loop [x 0]
        (loop [y 0]
          (paint-square g
                        ;START:compute-colors
                        ;;for each x,y coordinate compute the color
                        (reduce (partial compute-color x y) [0 0 0] balls)
                        ;END:compute-colors
                        x y step)
          (if (< y (- SIZE step)) (recur (+ y step))))
        (if (< x (- SIZE step)) (recur (+ x step))))

      (finally (.dispose g)))
    (if-not (.contentsLost buffer)
      (.show buffer)) ))

(defn metaball []
  {:x      (rand-int SIZE)
   :y      (rand-int SIZE)
   :vx     (inc (rand-int 6))
   :vy     (inc (rand-int 6))
   :radius (+ 40 (rand-int 15))
   :color  (repeatedly 3 #(rand-int 256))})

(defn start [& [num-balls]]
  (let [frame  (JFrame. "Metaballs")
        canvas (Canvas.)]
    (doto frame
      (.setSize SIZE SIZE)
      (.setDefaultCloseOperation JFrame/EXIT_ON_CLOSE)
      (.setResizable false)
      (.add canvas)
      (.setVisible true))

    (doto canvas
      (.createBufferStrategy 2)
      (.setVisible true)
      (.requestFocus))

    ;START:main-loop
    ;;run this in a loop where we move the
    ;;balls around and render them
    (loop [balls (repeatedly (or num-balls 2) metaball)]
      (draw canvas balls)
      (recur (map move balls)))
    ;END:main-loop
    ))