try to stop jitter

src/frontend/il/update.cljs

@@ -2,14 +2,14 @@
   (:require
    [frontend.il.entity :as entity]
    [cljs.core.async :as async]
-   [il.common.velocity :as v]))
+   [il.common.math :as ilmath]))
 
 (defn apply-velocity [e dt]
   (if (contains? e :velocity)
     (let [{x :x y :y vel :velocity} e
           {vx :x vy :y} vel
-          dtvx (* dt vx)
-          dtvy (* dt vy)]
+          dtvx (Math/floor (* dt vx))
+          dtvy (Math/floor (* dt vy))]
       (assoc e :x (+ x dtvx) :y (+ y dtvy)))
     e))
 
@@ -20,14 +20,20 @@
       (assoc e :renderable renderable))
     e))
 
+(def min-distance-for-update 1)
+
 (defn apply-server-position [e]
   (let [{:keys [x y tx ty]} e
         speed (get e :speed 15)
         has-server-pos (not (and (nil? tx) (nil? ty)))
         has-actual-pos (not (and (nil? x) (nil? y)))]
     (cond
+      (and (= x tx) (= y ty)) e
       (and has-server-pos (not has-actual-pos)) (assoc e :x tx :y ty)
-      (and has-server-pos has-actual-pos) (assoc e :velocity (v/velocity-for x y tx ty speed))
+      (and has-server-pos has-actual-pos) (let [delta (ilmath/euclidean-distance x y tx ty)]
+                                            (cond
+                                              (> delta min-distance-for-update) (assoc e :velocity (ilmath/velocity-for x y tx ty speed)
+                                              :else e)))
       :else e)))
 
 (defn apply-player-shoot [state mouse-pos]

src/il/common/constant.cljc

@@ -0,0 +1 @@
+(ns il.common.constant)

src/il/common/math.cljc

@@ -1,4 +1,4 @@
-(ns il.common.velocity)
+(ns il.common.math)
 
 (defn velocity-for [x y tx ty speed]
   (let [dx (- tx x)
@@ -9,3 +9,6 @@
     (if (zero? h)
       {:x 0.0 :y 0.0}
       {:x vx :y vy})))
+
+(defn euclidean-distance [x1 y1 x2 y2]
+  (Math/sqrt (+ (Math/pow (- x2 x1) 2) (Math/pow (- y2 y1) 2))))

src/il/constant.clj

@@ -1 +0,0 @@
-(ns il.constant)

src/il/handler.clj

@@ -1,6 +1,6 @@
 (ns il.handler
   (:require [il.state :as s]
-            [il.common.velocity :as v]))
+            [il.common.math :as ilmath]))
 
 (defn handle-position [_ state-chan player-id {x :x y :y}]
   (s/change state-chan update-in [:players player-id] assoc :x x :y y))
@@ -14,7 +14,7 @@
         {tx :x ty :y player :player} msg
         {x :x y :y} player
         speed 50 ; TODO: Get projectile speed from player weapon
-        velocity (v/velocity-for x y tx ty speed)
+        velocity (ilmath/velocity-for x y tx ty speed)
         bullet {:sprite "/sprite/projectile.png" ; TODO: Render sprite based on player weapon
                 :x x
                 :y y