Processing 1.0 - Processing Discourse - Many bouncing ball sketch problems

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Index › Programming Questions & Help › Programs › Many bouncing ball sketch problems

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Many bouncing ball sketch problems (Read 529 times)

TweakingKnobs

Many bouncing ball sketch problems
Dec 12^th, 2008, 4:11pm

I am doing the many bouncing ball sketch from the "creative coding and comp art" book, I think i got it all right but i cant run it it says it cannot find nothing named "i" altough i think i'ts there , here's the code.

Thanks !

Code:


// many bouncing bal program 

// global variables

int ballCount = 500;
int ballSize = 8;
int ballSpeed = 3;
float []xspeed = new float [ballCount];
float []yspeed = new float [ballCount];
float []xpos = new float [ballCount];
float []ypos = new float [ballCount];
float []wdth = new float [ballCount];
float[]ht = new float [ballCount];

//initialize sketch
void setup(){
  
  
  size (400,400);
  background(0);

  //initialize values for all balls
  
  for (int i=0; i<ballCount; i++)
  
  // set variable ball speed
  
  xspeed[i] = random(1, ballSpeed);
  yspeed[i] = random (-ballSpeed, ballSpeed);
  
  //ball varied ball sizes
  
  wdth[i] = random(1, ballsize);
  ht[i] = wdth[i];
  
  // set initial ball placement
  
  xpos[i] = width/2+random(-width/3, width/3);
  ypos[i] = height/2+random(-height/3, height/3);
}
}
// turnoff stroke

noStroke();
frameRate(30);


// draw

void draw(){
  
  // updates background
  
  beackground(0);
  
  for(int i=0; i<ballCount; i++){
    
    fill (i*255/ballCount);
    //drawballs
    
    ellipse(xpos[i],ypos[i], wdth[i],ht[i]);
    
   // upgrade ball pos
   xpos[i]+=xspeed[i];
   ypos[i]+=yspeed[i];
   
   // conditionals
   if (xpos[i]+wdth[i]/2>=width || xpos[i]<=wdth[i]/2){
     xspeed[i]*=-1;
   }
   if (ypos[i]+ht[i]/2>=height || ypos[i]<=ht[i]/2){
     yspeed[i]*=-1;
   }
  }
}

www.tweakingknobs.com&&&&Electronic Graphics and Computer Music

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: Many bouncing ball sketch problems Reply #1 - Dec 12^th, 2008, 5:32pm In setup(), the for loop has no opening brace, so only the first line (xspeed) knows i (scoped to the loop). I think the noStroke and frameRate calls should be in setup() too.

TweakingKnobs Full Member Offline Posts: 158	Re: Many bouncing ball sketch problems Reply #2 - Dec 12^th, 2008, 6:27pm thanks , but i dont really understand what you mean, i see one brace in the for loop, could you explain or copy , modify and paste the code please ? thanks !
	www.tweakingknobs.com&&&&Electronic Graphics and Computer Music

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: Many bouncing ball sketch problems Reply #3 - Dec 12^th, 2008, 6:58pm Problem of vocabulary: for me (and many people) - ( is parenthesis - { is brace (also called soft brace) - [ is square brace - < is angle brace I know the terminology varies with culture, country and people. You should put a (soft) brace { at the location where you have the caret in your screenshot.

TweakingKnobs Full Member Offline Posts: 158	Re: Many bouncing ball sketch problems Reply #4 - Dec 12^th, 2008, 7:47pm thanx , i tried but it still wont run, i also tried puting a closed curly brace at the end and many other ways but just cant get it. Have you tried running the sketch ? could you post the solution please ?thanks !
	www.tweakingknobs.com&&&&Electronic Graphics and Computer Music

sw01

Re: Many bouncing ball sketch problems
Reply #5 - Dec 12^th, 2008, 8:12pm

Curly brace is where you place the code that you want repeated in a for statement.

A didactic code:

for(int i = 0; i < 10; i++){

println( "I am at:"+i);

}

// and also, just to show that spaces and returns are just
// decorations to make it easier for you to read the code:

for(int i = 0; i < 10; i++){ println( "I am at:"+i); }

// above is exactly the same code.

// 10 is where you place your ballcount variable.

// as PhiLho said, please note the differences between
// the type of parenthesis/brackets.

rebirth Junior Member Offline Posts: 54	Re: Many bouncing ball sketch problems Reply #6 - Dec 12^th, 2008, 8:18pm Or you can say bracket instead of brace.

TweakingKnobs Full Member Offline Posts: 158	Re: Many bouncing ball sketch problems Reply #7 - Dec 12^th, 2008, 8:57pm man i am ver thankfull for all your help , but look i tried allready many ways and i just cant get it , could you please post the right code. thanks !
	www.tweakingknobs.com&&&&Electronic Graphics and Computer Music

PhiLho

Re: Many bouncing ball sketch problems
Reply #8 - Dec 12^th, 2008, 9:46pm

OK, here is the working code, look at my //--> remarks...
Code:

// many bouncing bal program  
 
// global variables
 
int ballCount = 500;
int ballSize = 8;
int ballSpeed = 3;
float []xspeed = new float [ballCount];
float []yspeed = new float [ballCount];
float []xpos = new float [ballCount];
float []ypos = new float [ballCount];
float []wdth = new float [ballCount];
float[]ht = new float [ballCount];
 
//initialize sketch
void setup(){
   
   
  size (400,400);
  background(0);

//--> I moved that up, as said
// turnoff stroke
 
noStroke();
frameRate(30);
 
  //initialize values for all balls
   
  for (int i=0; i<ballCount; i++)
  { //--> I added this curly/soft brace
  // set variable ball speed
   
  xspeed[i] = random(1, ballSpeed);
  yspeed[i] = random (-ballSpeed, ballSpeed);
   
  //ball varied ball sizes
   
  wdth[i] = random(1, ballSize); //--> Also corrected here, case is important
  ht[i] = wdth[i];
   
  // set initial ball placement
   
  xpos[i] = width/2+random(-width/3, width/3);
  ypos[i] = height/2+random(-height/3, height/3);
}
}
 
 
// draw
 
void draw(){
   
  // updates background
   
  background(0); //--> Fixed a typo here!
   
  for(int i=0; i<ballCount; i++){
     
    fill (i*255/ballCount);
    //drawballs
     
    ellipse(xpos[i],ypos[i], wdth[i],ht[i]);
     
   // upgrade ball pos
   xpos[i]+=xspeed[i];
   ypos[i]+=yspeed[i];
   
   // conditionals
   if (xpos[i]+wdth[i]/2>=width || xpos[i]<=wdth[i]/2){
     xspeed[i]*=-1;
   }
   if (ypos[i]+ht[i]/2>=height || ypos[i]<=ht[i]/2){
     yspeed[i]*=-1;
   }
  }
}

TweakingKnobs Full Member Offline Posts: 158	Re: Many bouncing ball sketch problems Reply #9 - Dec 12^th, 2008, 10:33pm Thank you so much ! i would never see all those things !!! 8D
	www.tweakingknobs.com&&&&Electronic Graphics and Computer Music

TweakingKnobs Full Member Offline Posts: 158	Re: Many bouncing ball sketch problems Reply #10 - Dec 13^th, 2008, 2:10am what should i do to get all the balls white? i dont understand where the code tells the balls to be one color . thanks !
	www.tweakingknobs.com&&&&Electronic Graphics and Computer Music

TweakingKnobs Full Member Offline Posts: 158	Re: Many bouncing ball sketch problems Reply #11 - Dec 13^th, 2008, 2:11am i ogt it , 255 in the fill option. but how to make it a random alpha value , but only in whites ?
	www.tweakingknobs.com&&&&Electronic Graphics and Computer Music

rebirth Junior Member Offline Posts: 54	Re: Many bouncing ball sketch problems Reply #12 - Dec 13^th, 2008, 2:19am TweakingKnobs wrote on Dec 13^th, 2008, 2:11am: i ogt it , 255 in the fill option. but how to make it a random alpha value , but only in whites fill(color(255,255,255,random(255)));

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