You don't declare a variable called xRand within your class... you access the global one every time.

Thanks for your reply.

I thought everytime the for loop in setup ran it should create a new xRand value and associate it with an object each time. Obviously I'm wrong, but then should I not have a global xRand?

Thanks,

Shane

Ok I think I understand now.

Line 31. should be

  float x, y, xRand, diameter, frequency;

That works now thanks for your help,

Shane

Yes, you have a global xRand and an xRand within the class. The local one will override the global one. The only problem with this is that it can be difficult to detect errors such as yours.

Yes, I see it now. I'm very new to OOP. Thanks

Hi,

I'm not sure if I should be posting a new thread. But anyway, I am trying to get a random set of dots to start oscillating only when a particular dots passes them.

Running the following code will make it obvious what I am trying to do. The core of the problem is I think line 47. equlib is a randomly generated x-coordinate about which each dots oscillates.

1. int numSpots = 10;
2. int amplitude = 30;
3. float frequency = PI/(numSpots*30), angle;
4. //Declare and create the array
5. Spot[] spots = new Spot[numSpots];
6. void setup() {
7.   size(600, 300);
8.   smooth();
9.   noStroke();
10.   for (int i = 0; i < spots.length; i++) {
11.     float x = random(50, width-amplitude);
12.     float equilib = x;
13.     float xGlide = 10;
14.     float y = random(30, height/2);
15.     //Create each object
16.     spots[i] = new Spot(x, equilib, xGlide, y, 10, frequency);
17.   }
18. }
19. void draw() {
20.   fill(0);
21.   rect(0, 0, width, height);
22.   fill(255);
23.   for (int i = 0; i < spots.length; i++) {
24.     if (i==0) {
25.       spots[0].glide();
26.       spots[0].display();     
27.     }
28.     else {
29.       spots[i].move(); //Move each object
30.       spots[i].display(); //Display each object
31.     }
32.   }
33. }
34. class Spot {
35.   float x, y, equilib, xGlide, diameter, frequency;
36.   int direction = -1;
37.   //Constructor
38.   Spot(float xpos, float equilibpos, float xGlidepos, float ypos, float dia, float fr) {
39.     x = xpos;
40.     xGlide = xGlidepos;
41.     equilib = equilibpos;
42.     y = ypos;
43.     diameter = dia;
44.     frequency = fr;
45.   }
46.   void move() {
47.     if (equilib < xGlide) {
48.       x = equilib + (sin(angle))*amplitude;
49.       angle += frequency;
50.       println(angle);
51.     }
52.   }
53.   void display() {
54.     ellipse(x, y, diameter, diameter);
55.   }
56.   void glide() {
57.     xGlide += 1.0;
58.     x = xGlide;
59.   }
60. }
61. boolean bStop;
62. void mousePressed()
63. {
64.   bStop = !bStop;
65.   if (bStop)
66.     noLoop();
67.   else
68.     loop();
69. }

Thanks again,

Shane

Hi,

yes, in line 47 you compare "equilib" to "xGlide", but you never update xGlide, so it stays 10 all the time.
You could instead compare equilib to the x-value of the first spot.

1.         if (equilib < spots[0].x) {
   

Iron13,

Ah now I see how to use a specific variable in a specific object. That does solve that problem.

But they all oscilate in phase now, I want them to start when the dot passes from their equilibrium position. This way they should all be out of phase with each other.

Thanks for your help.

Shane

That's because you only have one gloabel 'angle'-variable.
Remove it from the top of your sketch and add it as a local variable of Spot, i think then it works the way you want.

Think of classes as blueprints, and each new SomeClass() creates an object (an instance) of the class / blueprint with a fresh set of variables (called fields in Java), independent of the others (except for static variables, but that's something not used in the Processing world, as global variables do the same thing).
As a rule of thumb, each class should be independent of the remainder of the code, ie. they should use global variables as little as possible. With some exceptions: globally defined constants, or values that really need to be shared (eg. mouseX).
Thus, you will avoid side effects, like changing a global variable in an instance, that will affect all the other objects.

Thanks for the explanation. I see what you both mean now and that I should use global variables as little as possible.

I changed the angle varibale, making a local variable within Spot and it workin now.

I am going to start a new thread to ask the question is OOP more or less memory and processing intensive than storing variables in an array? This is becasue the OOP version is now crashing on me.

Thanks,

Shane