Added joint path drawing

pendel.py

@@ -45,6 +45,13 @@ class PendelSim(Game):
         self.init_data()
         self.mousedown = False
         self.mousepos = (0,0)
+        self.pathsurface = pygame.Surface( (self._width, self._height) )
+        self.resetpath()
+
+    def resetpath(self):
+        BLACK = (0,0,0)
+        self.pathsurface.fill( BLACK )
+
 
     def init_data(self):
         self.staff_lengths = staff_lengths = [ randint(150,200), randint(100,200), randint(100,150) ]
@@ -54,6 +61,7 @@ class PendelSim(Game):
         joint_c = joint_b - Vector(-staff_lengths[2],0)
         self.joints = [fixed_joint, joint_a, joint_b, joint_c ]
         self.joint_speed = [ Vector(0,0), Vector(0,0), Vector(0,0), Vector(0,0) ]
+        self.old_joints = self.joints
 
     def on_update(self, dtime):
         new_joints = self.joints[:]
@@ -71,6 +79,7 @@ class PendelSim(Game):
         for i in range(0,4):
             self.joint_speed[i] = (new_joints[i] - self.joints[i]) / dtime
 
+        self.old_joints = self.joints
         self.joints = new_joints
 
     def on_render(self, surface):
@@ -80,9 +89,12 @@ class PendelSim(Game):
         WHITE = (255,255,255)
         BLUE = (0,0,255)
 
-        staff_colors = [ RED, GREEN, BLUE ]
+        staff_colors = [ GREEN, RED, BLUE ]
 
-        surface.fill(BLACK)
+        for i in range(2,4):
+            pygame.draw.line(self.pathsurface, staff_colors[(i-1)%3], self.old_joints[i].astuple(), self.joints[i].astuple(), 2)
+
+        surface.blit(self.pathsurface, (0,0))
 
 
         for i in range(4-1):
@@ -100,6 +112,7 @@ class PendelSim(Game):
         elif event.type == MOUSEBUTTONUP:
             self.mousedown = False
             self.mousepos = event.pos[:]
+            self.resetpath()
         elif event.type == MOUSEMOTION:
             self.mousepos = event.pos[:]
         else: