3. float orbitDuration = 5*1000; // 5 second orbit
4. float orbitRad = 50;
5. 
   
6. void setup()
7. {
8.   size(400,400);
9. }
10. 
    
11. void draw()
12. {
13.   background(255);
14.   translate(width/2,height/2);
15.   ellipse(0,0,50,50);
16.   float ang = TWO_PI * millis()/orbitDuration;
17.   float x = cos(ang)*orbitRad;
18.   float y = sin(ang)*orbitRad;
19.   ellipse(x,y,5,5);
20. }

1. float px, py, vx, vy; 
2. 
   
3. void setup() {
4.   size(400, 400);
5.   ellipseMode(CENTER);
6.   reset();
7. }
8. 
   
9. void reset() {
10.   py = 0;
11.   px = 50;
12.   vy = -1;
13.   vx = 0;
14. }
15. 
    
16. void draw() {
17.   simulate();
18.   render();
19. }
20. 
    
21. void simulate() {
22.   float ax = -px / sq(dist(0,0,px,py));
23.   float ay = -py / sq(dist(0,0,px,py));
24.   vx+=ax;
25.   vy+=ay;
26.   px+=vx;
27.   py+=vy;
28. }
29. 
    
30. void render() {
31.   background(255);
32.   translate(width/2.0, height/2.0);
33.   ellipse(0, 0, 50, 50);
34.   ellipse(px, py, 5, 5);
35. }

For more ways to make things go in circles, check out Jim Blinn's awesome 1987 book "Jim Blinn's Corner: A trip down the graphics pipeline".  The first chapter offers 15 algorithms for drawing circles, many of which are applicable here...

Thank guys for replying.

 

  Thanks jbum for the code and idea. I will try it and modify it to my needs. I see you are using trig to calculate the co-ordinate. And using translate(). Interesting...

 

  Also thanks tfguy44 for your code and idea. I will look into your idea also.

 

Anyway, I did check my variables using println() and a millis() to check the time delay... It about stable of 31 ms to 32 ms. A bit "sluggish".

 

I did a code to simulate a planet orbiting a sun with a moon. My idea work, But still the "slow & fast" swing. Mmm..

 

The code :

 

1. planetary orbits are generally ellipses, not only circles
   (they can also be hyperbolas or parabolas, but i don't think you'll want those)
2. the word "orbit" usually means only the shape of the curve, opposed to the planetary motion (which is how fast you "walk" through the different parts of the curve)

that said, @jburns code is definitely correct for circular orbits/movements, 

if you would like to generalize a bit, 

here's some iterative code that simply simulates gravity: 

------ 

edited to so that F ~ 1/r^2, not F ~ 1/r as the code wrongly used before

Thanks you guys for the ideas. I hope you guys try my code to see what I am planning to do and what I mean by the "swing" problem. 

 

@kritzikra

 

I do agree most orbits are  ellipse and parabolas <-- long stretch ellipse. I will study and try your code, try to integred your code and use it for a moon orbit.  

 

Right now, my idea is to simulate the solar system, maybe "alien" planetary system ( binary star system ), or some planetary systems in one of the Star-Trek book that I have ( Vulcan or Romulan ), or maybe Star Wars star systems - ( Taboo or Endor )  <-- I am a bit a Sci-Fi fan

 

In my code, I use this formula of the circle :   x^2 + y^2 = r^2   or the ellipse : x^2/a^2 + y^2/b^2 = 1 ( The formulas came from : Basic Technical Mathematics With Calculus by Allyn J. Washington - 4th Edition - Metric Version

 

Oh yeh, my code is a bit "long". I wonder how to integraded your guys code, making class , using my code ( to much repetition ) .... Oh well, I wil figure it out in time.

 

Bear in mine that I am not a student, I am just doing this "programing pratice" on my own time and for the fun of it.

 

    

 

 

 

You asked about reducing the size of your code.  I've reduced the size of your program by representing your two orbiting bodies as a single class, and getting rid of all the duplicate variables and functions.  The velocity errors are still there, and I suspect they are either due to typos in your transcription, or errors in the original book you're quoting from.  I'm not going to fix those, cause I think this system for moving bodies is simply broken (in 2011, you shouldn't be doing trying to do physics using integer math.  Also, having a separate function for each quadrant is crazy).  But this will give you an idea for how you can shorten your existing code:

 

@jbum

 

Thank for helping out. ( Don't forget, I am not an experience programer - and try to figure this out will be tought ) I use the integer math because of the testing condition and counting,  The quadrant to help the program. ( I know you way is better ) . I will study your code,  I just notice you use the vector-polar ( r,angle ---> x,y ) calculation. And a class function. I will try to figure out your logic being your code.  And I will also study kritzikra's code. He is using Pvector.. that I have to "study". 

 

About my "problem", I was thinking if I can do it in slow motion, so I put a delay(2000);  and monitor my variable, my code behave correctely. The "swing" and the orbit behave like a circle being draw with Paint - bmp. A bmp representation of a circle. Not to many circles being draw at the top / bottom compare to the sides whish will explain the "fast" look.

 

Guys, I will challenge myself, I will do a solar system ( not Earth ) but the fictional Vulcan star system. It is base in the book : Star-Trek - The Worlds of the Federation by Shane Johnson. The Vulcan system is compose of 3 planet. one planet orbit like Venus or Mercury, the other two are in "trojan" orbit, one with a moon.  I will "draw" the star system to show what I mean.  That will help me out to pratice coding in Processing. ( Hey , I like Star-Trek OK...) And thanks of you guys ideas., will help a lot. 

 

@tfguy44.

 

I having a hard time to figure out your logic and were your fornula came from. Here the section that I having a hard time to figure out. I understand dist() function, It a this : r=sqrt(sq(Side_X)+sq(Side_Y));  and the px and py , those parts I get it, but the rest is ???

 

Here the code that I am trying to figure out.

 

1. void simulate() {
2.   float ax = -px / sq(dist(0,0,px,py));
3.   float ay = -py / sq(dist(0,0,px,py));
4.   vx+=ax;
5.   vy+=ay;
6.   px+=vx;
7.   py+=vy;
8. }

     

 

 

p.s. i'm not sure if you're more interresting in how planetary motions 

work or more in the star trek solar system. in case you want to move 

to a higher level of abstraction you should consider a library like this. 

@kritzikra

 

Thank you for your highlight about your code, using gravity and explain the code of tfguy44. And send me the link.  To amswer your quote, I am interested in both. Since the discovery of a lots of planets and stars outside our solar system, a fictional solar system could look like one of them  being discover.  Thank you very much for your info, I will study it, I do have an understanding of it ( gravity, force, speed, acceleration ), and try to challenge myself to code a orbit program using an orbital  ellipse instead.

 

Edit - kritzikra, I try your code that your re-edit, well just say the old one work fine. The new one is doing this : the planet is getting away outside the screen, and don't come back... The old one do, not a perfect circle, and not ellipse either, more like a "wobble" orbit, so I experiment by comment  the rect(); and see what happen... it create a trace that stay on, the planet create a "range" or a "ring" around the sun, the "ring" is a "circle" fill by multi-passing of the planet. I don't think Earth behave just like your code, if it does, the "ring" is not that big, you will know by the weather / temperature outside your home ( closer to the sun - hot like hell - away from the sun - cold like the South pole )...My opinion    

 

@jbum

 

Thank of your Class Planet Orbit code, I use your class, write a code to simulated the fictional Vulcan star system base on the book : Star-Trek - The Worlds of the Federation by Shane Johnson. The challege is the main planets is in trojan orbit, include a moon, so I create 5 Body, 4 real, 1 imaginay,  The "real" - one orbit the star, the two trojan orbiting a point , which the point orbit the star, the point is the imaginary, the moon simply orbit one of the trojan planet. I know the code use trigometry calculation (  polar-rectangular ).

 

Edit -  Next is to re-modify the class to take into account the movement direction ( clock wise / counter clock wise ) and going into an ellipse instead of a circle. ( I will find a fornula to use in a polar-rectangular calculation )  

 

Here the code that show a trojan orbit :

 

Re-edit : I change a few little things in the code.