Processing Forum

Why my function is not working as intended?

[1 Reply]
- 13-Nov-2011 05:33 AM
- Forum: Programming Questions
Hello again Processing Forum,
For the past two days, I've been working on one of the questions in my coursework. The question and the incomplete sketch is as follows:

"Develop some aspects of a very simple game, in Processing. The attached is an incomplete version of a game called Breakout....You need to develop the code as discussed below, to make the game work appropriately...You may add variables as necessary, and additional functions if needed...First complete the functions checkBallAgainstBat()...to do what is specified by them."

I have left out some parts of the coursework question which I feel were unnecessary towards addressing the issue. The first part of my task is to complete the function checkBallAgainstBat(). I highlight my attempts to accomplish this in blue.
1. //Basic Breakout game
2. //Code from Matthew Yee-King
4. //brick position
5. float brickX;
6. float brickY;
8. //brick width and height
9. float brickH;
10. float brickW;
12. //ball position
13. float ballX;
14. float ballY;
16. //ball diameter
17. float ballD;
19. //ball direction
20. float ballDx;
21. float ballDy;
23. //bat position
24. float batX;
26. //bat width
27. float batW;
28. float batH;
30. //bat colour
31. float batB;
33. void setup() {
34. size (500, 500, P2D);
35. // set sizes of game items
36. brickW = 100;
37. brickH = 50;
38. batW = 100;
39. batH = 25;
40. ballD = 25;
41. batB = 255;
42. //random brick position
43. brickX = random(0, width - brickW);
44. brickY = random(0, height/2);
45. // bat in the centre
46. batX = (width/2) - (batW/2);
47. //ball atop bat
48. ballX = batX + (batW/2);
49. ballY = height - batH - (ballD/2);
50. //ball movement
51. ballDx = random(-5, 5);
52. ballDy = -5;
53. rectMode(CORNER);
54. ellipseMode(CENTER);
55. frameRate (12);
56. }
58. void draw() {
59. //check for ball collision
60. //with top or sides of bat
61. checkBallAgainstBat();
62. //check for ball collision with
63. //left right and top walls
64. //and bounce
65. checkBallAgainstWalls();
66. //check ball against brick
67. checkBallAgainstBrick();
69. //move the ball
70. ballX += ballDx;
71. ballY += ballDy;
72. background(0);
73. //draw the bat
74. fill(0, 255, 0);
75. rect(batX, height - batH, batW, batH);
76. //draw the brick
77. fill(0, 0, batB);
78. batB = (batB +10) % 255;
79. rect(brickX, brickY, brickW, brickH);
80. //draw the ball
81. fill(255, 0, 0);
82. ellipse(ballX, ballY, ballD, ballD);
84. if (keyCode == 37) { // left cursor key
85. batX -= 10;
86. //keep it on the screen
87. if (batX < 0) {
88. batX = 0;
89. }
90. }
91. if (keyCode == 39) { //right cursor key
92. batX += 10;
93. if (batX > (width - batW)) {
94. batX = width - batW;
95. }
96. }
97. }
99. //when they let go of they key, reset the keyCode
100. void keyReleased() {
101. keyCode = -1;
102. }
104. //this function checks if the ball has hit the top or sides of the bat and
105. //update its
106. //direction as appropriate so the ball bounces off the bat
107. void checkBallAgainstBat(){
108. if ((ballY + ballD/2 > height - batH) && (ballX >= batX && ballX <= batX + batW)){
109. ballDy *= -1;
110. }
111. if ((ballX + ballD/2 <= batX || ballX - ballD/2 >= batX + batW) && (ballY >= height - batH && ballY <= height)){
112. ballDx *= -1;
113. }
114. }
116. //this function checks if the ball has hit the brick. It should bounce off
117. //the brick and return true if so
118. boolean checkBallAgainstBrick() {
119. return false;
120. }
122. //this function checks if the ball has hit the top, left or right
123. //walls and update its
124. //direction as appropriate so the ball bounces off the walls
125. void checkBallAgainstWalls(){
126. if (ballX + ballD/2 > width){// right wall
127. ballDx *= -1;
128. }
129. if (ballX - ballD/2 < 0){// left wall
130. ballDx *= -1;
131. }
132. if (ballY - ballD/2 < 0){// top wall
133. ballDy *= -1;
134. }
135. }
My train on thought is if "the edge of the ball" touches the "sides of the bar", the ball's direction should be altered along it's x-axis. However my sketch does not work as what I had originally intended when translated to code.
I'm hoping I can get some detail explanations as to why my approach to the function does not work, and will appreciate if someone can rectified my logic (or the lack there-off) and equip me with new insights so I can tackle the question armed with new knowledge.

questions by a noob 'processor',

derrick.

Why "mouseButton=true" & "mousePressed=false"?

[3 Replies]
- 11-Nov-2011 10:34 PM
- Forum: Programming Questions
Greetings Processing Forum,
I've been doing revision on Processing and was going through some of the chapters in the Processing Reference Book "...Programming Handbook for Visual Designers...". I was tinkering with some codes from the Chapter "Input 1: Mouse 1" and I tried to do some minor modification to one of the sketch examples. The example looks like this initially:
1. void setup() {
2. size (100, 100);
3. noCursor();
4. }
5. void draw() {
6. background(204);
7. if (mousedPressed == true) {
8. cursor();
9. }
10. }
The intent of this sketch is to exhibit this: "If noCursor() is run, the cursor will be hidden while the program is running until the cursor() function is run to reveal it."
I modified the codes to the following because I wanted the user to be able to revert the programme back to a state where no cursor is shown. However it only works if I use the "mouseButton" system variable instead of the "mousePressed" system variable. I don't see why mousePressed should not work and will greatly appreciate if you guys/girls can explain to me why this is so.
2. void setup() {
3. size(100, 100);
4. noCursor();
5. }
6. void draw() {
7. background(204);
8. if (mousePressed == true) {
9. if (mousePressed == LEFT) {
10. cursor();
11. } else if (mousePressed == RIGHT) {
12. noCursor();
13. }
14. }
15. }

New to Processing

[5 Replies]
- 08-Nov-2011 07:30 PM
- Forum: Programming Questions
int x,y;
int dx=1,dy=1;
int screenHeight=500;
int screenWidth=500;
int sz = 10;
int barX1=10, barY=screenHeight/2;
int barX2=50;
int score=0;

void setup(){
size(screenWidth,screenHeight);
fill(255);
stroke(255);
frameRate(100);
smooth();
x=int(random(0,screenWidth));
y=int(random(0,screenHeight));
}

void draw(){

background(0);
line(barX1,barY,barX2,barY);
ellipse(x,y,sz,sz);

//detect if ball hit left and right side
if(x<=sz/2 || x>=screenWidth-sz/2)
dx=-dx;

//detect if ball hit top and bottom
if(y<=sz/2 || y>=screenHeight-sz/2)
dy=-dy;

//detect if bar hits ball
if((y==barY-sz/2 || y==barY+sz/2 ) && (x>barX1 && x<barX2))
{
dx=-dx;
dy=-dy;
println(++score);
}

x+=dx;
y+=dy;
}

void keyPressed() {
if (key == CODED) {
if (keyCode == LEFT) {
barX1-=10;
barX2-=10;
} else if (keyCode == RIGHT) {
barX1+=10;
barX2+=10;
} else if (keyCode == UP) {
barY-=10;
} else if (keyCode == DOWN) {
barY+=10;
}
}
}

This is a sketch from my lecture on 'Motion'. We are given the additional task of modifying this set of code and transforming it into a 'Ping-Pong' game where the participation of another player is possible. However, I'm having some trouble interpreting this code, and so I've taken liberties to pose my questions to the web in hopes for guidance. Any form of help rendered will be appreciated.

Some questions I have pertaining to the aforementioned code:

Q1) Is screen.height the same as screenHeight? and additively, Is screen.width the same as screenWidth?

Q2) Why set the fill(255) in void(setup) only to set the background(0) in void(draw)?

Q3) //detect if ball hit left and right side
if(x<=sz/2 || x>=screenWidth-sz/2)
dx=-dx;

Why sz/2 of all values? ( I tried substituting this set of values with alternative values of "sz/3", "sz/4", "sz/30" and did not see any visible changes when running the programme.

I'm new to coding and programming and although technically I should be acquainted with the principles of "motion" at this point in time. Reality says otherwise. Any form of assistance will be deeply appreciated =).

On a sidenote, I'm also curious as to whether or not there are good practice habits or methodologies that should be adopted for beginners who are just starting out in programming.

I'm currently a student of the University of London International Programme in my first year of the Creative Computing Degree. Geographically I'm located in Singapore but spiritually I belong to the web. And if there's anyone out there, like me who is just starting out on Processing and is keen to engage in collaborative learning, feel free to add me on facebook =D.

Activity Trend