fix: add engine time

src/main.cpp

@@ -34,26 +34,39 @@
 // stuff to a library, since it keeps input a separate concern from the physics model
 struct Input
 {
-    bool cycleAnimation;
+    bool pauseTime;
 } input;
 
+
 void keyCallback(GLFWwindow* window, int key, int scancode, int action, int mods)
 {
-    if (key == GLFW_KEY_C && action == GLFW_PRESS)
+    if (key == GLFW_KEY_SPACE && action == GLFW_PRESS)
     {
-        input.cycleAnimation = true;
+        input.pauseTime = true;
     }
 }
 
 void clearInput()
 {
-    input.cycleAnimation = false;
+    input.pauseTime = false;
 }
 
-double getTime()
+// now should always increase linearly with real world time, this should not be modified by input
+// for animations etc
+struct Time
 {
-    auto now = std::chrono::steady_clock::now().time_since_epoch();
-    return std::chrono::duration<double>(now).count();
+    double now;
+    double dt;
+} engineTime;
+
+void updateTime()
+{
+    std::chrono::duration timeSinceEpoch = std::chrono::steady_clock::now().time_since_epoch();
+    double now = std::chrono::duration<double>(timeSinceEpoch).count();
+    double dt = now - engineTime.now;
+
+    engineTime.dt = dt;
+    engineTime.now = now;
 }
 
 int main()
@@ -100,11 +113,12 @@ int main()
     glfwSetKeyCallback(window, keyCallback);
 
     // TODO: convert these to an enum
-    const int ANIM_ORBITING     = 0;
-    const int ANIM_ECCENTRICITY = 1;
-    int animation = 0;
+    const int MODE_ORBIT     = 0;
+    const int MODE_MANEOUVRE = 1;
+    int mode = 0;
 
-    double time = getTime();
+    // simulation time. this can be paused or whatever as animation demands.
+    double time = 0;
 
     // Main loop
     while (!glfwWindowShouldClose(window))
@@ -113,14 +127,15 @@ int main()
         // clearInput() needs to be called to clear input from previous frame
         clearInput();
         glfwPollEvents();
+        updateTime();
 
         // apply input
-        if (input.cycleAnimation)
+        if (input.pauseTime)
         {
-            animation++;
-            if (animation > ANIM_ECCENTRICITY)
+            mode++;
+            if (mode > MODE_MANEOUVRE)
             {
-                animation = 0;
+                mode = 0;
             }
         }
 
@@ -128,15 +143,14 @@ int main()
         // increase the speed of time by 60 * 60 * 24 to see 1 day per second.
         const double speed = 60 * 60 * 24;
 
-        // only update time if playing the orbiting animation
-        if (animation == ANIM_ORBITING)
+        // orbit modifications need to be instanteneous
+        if (mode == MODE_ORBIT)
         {
-            time = getTime() * speed;
+            time += engineTime.dt * speed;
         }
         else
         {
-            double e = .25 + .2 * sin(getTime());
-            moonOrbit.setEccentricity(e);
+            printf("maneouvre mode!\n");
         }
 
         // rendering