Processing Forum

What does % mean?

[3 Replies]
- 14-Jun-2012 11:43 PM
- Forum: Programming Questions
This is such a basic question but I cant find an answer.

in something like
1. if (i%20 == 0) {
2. line(i, 29, i, height/2);
what does the '%' operator do and mean?
Thanks.

Pretty lost with making a this small program.

[5 Replies]
- 20-May-2012 05:02 AM
- Forum: Programming Questions
Basically I have to write a program where its divided into quaters and once the

program starts, a ball is displayed in the centre of one quadrant. The ball has a fixed

radius but a randomly set color. Then I can click the ball and drag it to a different quadrant. The ball is displayed when being dragged. The destination quadrant is the one where the mouse is released. The ball is displayed in the centre of the destination quadrant with a new randomly set color.

I understand what needs to be done on paper I just have no idea how to go about it. My methods for defining class Ball didnt work and ive been stuck ever since.

Thanks for any help.

question about color in my code

[2 Replies]
- 13-May-2012 04:14 AM
- Forum: Programming Questions
Basically we were given a template and had to fill in some blanks to create the balls and then make them move and collide.

The last problem I am having is I need the balls colors to be randomised each run of the program from and RBG scale.

This is simple enough to do by making 3 floats and making them random (0, 255), but this isnt how they want us to do it, they want us to use color.

Thanks for any help in advance :)

Here is the code so far
2. class Ball {
3. float rad; // radius
4. float x,y; // center's position of the ball
5. float speedX; // for horizontal speed
6. float speedY; // for vertical speed
7. color c; // color of the ball
9. // constructor for initialization
10. Ball() {
11. rad = random (20, 40);
12. x = random (0+rad, width-rad);
13. y = random (0+rad, height-rad);
14. speedX = random (-5, 5);
15. speedY = random (-5, 5);
16. c = random (0,255);
17. // write some code
18. }
20. // display a ball with the given x, y and rad, filled with c
21. void display() {
22. fill(c);
23. noStroke();
24. ellipse(x, y, rad*2, rad*2);
25. }
27. // set the new position according to speedx and speedy
28. // and check if a bounce happens
29. void moveBall() {
30. x += speedX;
31. y += speedY;
32. if (x > width-rad || x < 0+rad)
33. speedX *= -1;
34. if ( y > height-rad || y < 0+rad)
35. speedY *= -1;
36. }
38. // dispaly a ball and let it move
39. void play() {
40. display();
41. moveBall();
42. }
44. // check if collision happens
45. // returns true two balls collide; otherwise returns false
46. boolean collideWith(Ball other) {
47. float gap = dist(x, y, other.x, other.y);
48. if (gap <= rad + other.rad)
49. return true;
50. else
51. return false;
52. }
53. }
56. // don't change anything below
57. Ball b1, b2;
59. void setup() {
60. size(400, 400);
61. b1 = new Ball();
62. b2 = new Ball();
63. smooth();
64. }
66. void draw() {
67. background(255);
69. if (b1.collideWith(b2)) {
70. b1.display();
71. b2.display();
72. }
73. else {
74. b1.play();
75. b2.play();
76. }
77. }

Need to record a collision between two objects.

[3 Replies]
- 29-Apr-2012 10:52 PM
- Forum: Programming Questions
Hello, am having 2 problems with this code I am trying to write. I need to make the black ball continue to rise on its own after keyPressed. At the moment I need to hold down a key for it to continue to rise which is wrong however I dont know how to fix it.

The second problem is I have no idea how to make the code register the 2 balls colliding, and then stopping the program and making the screen go blank. If the 2 balls dont collide then the black ball can go off the screen and then the program also stops.

Thanks in advance for any help.

Here is my code so far.
1. int x = 0;
2. int y = 0;
3. int speedX = 1;
4. int speedY = 1;
5. int goUp = 1;
7. void setup() {
8. size(200,200);
9. smooth();
10. }
12. void draw() {
13. background(255);
14. stroke(0);
15. line(0,61,width,61);
16. move();
17. bounce();
18. display();
19. blackEllipse();
20. keyPressed();
21. }
23. // A function to move the red ball.
24. void move() {
25. // Change the x and y location by speed.
26. x = x + speedX;
27. y = y + speedY;
28. }
30. // Bounce the red ball.
31. void bounce() {
32. // If the ball hits an edge, reverse the speed.
33. if ((x > width-40) || (x < 0)) {
34. speedX = speedX * - 1;
35. }
36. if ((y > 21) || (y < 0)) {
37. speedY = speedY * - 1;
38. }
39. }
41. // A function to display the ball
42. void display() {
43. noStroke();
44. fill(255,0,0);
45. ellipse(20+x,20+y,40,40);
46. }
47. // A function to display the black ball.
48. void blackEllipse() {
49. fill(0);
50. ellipseMode(CENTER);
51. ellipse(width/2,height-20+goUp,40,40);
52. }
54. void keyPressed() {
55. if (keyPressed) {
56. goUp = goUp-1;
57. }
58. }

rectangle which has 2 set co-ordinants and 2 which follow the mouse position.

[8 Replies]
- 25-Apr-2012 05:39 PM
- Forum: General Discussion
Hello,

I am quite new to processing and need to figure out a way to write a small program which waits for a mouse button press and then draws a rectangle from the starting point at which the mouse button was pressed to the current location of the mouse. And when the button is released the rectangle needs to disappear.

I am completely lost with how to go about this.

There are some other elements required for the program but I want to figure out how to do those on my own.

Thanks for any help.

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