Processing 1.0 - Processing Discourse - Odd behavior on Coordinates

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Odd behavior on Coordinates (Read 834 times)

buzoo

Odd behavior on Coordinates
Jul 24^th, 2005, 6:46am

I'm making a very simple beginner program that draws a random line-graph. After each frame, x increases by one, and y randomly increases or decreases.
When the user clicks, a rectangle is drawn as a way to clear the previous frame.
What's odd is that after the rectangle is drawn, the point starts not at x = 0, but some values over. But when I delete the line with the rect function, the point does start at 0...
Why the difference? Am I missing something?

Code:


float x, y;
void setup(){
  size(300, 300);
  colorMode(RGB, 100);
  background(50);
  rectMode(CENTER);
  x = 0;
  y = height/2;
}

void draw(){
  point(x, y);
  if(random(100)<50){ 
    y = y+1;
  }
  else{ 
    y = y-1;
  }
  x = x+1;

  if (mousePressed==true){ 
    fill(50);
    rect(width/2, height/2, width, height);
    if(x>width){
	x = 0;
	y = height/2;
    }
  }
}

mark hill

Re: Odd behavior on Coordinates
Reply #1 - Jul 24^th, 2005, 10:46am

Your not setting x to 0 after the mousePressed flag. My understanding is that you want an x reset after button pressed.

Code:


float x, y; 
void setup(){ 
  size(300, 300); 
  colorMode(RGB, 100); 
  background(50); 
  rectMode(CENTER); 
  x = 0; 
  y = height/2; 
} 
 
void draw(){ 
  point(x, y); 
  if(random(100)<50){  
    y = y+1; 
  } 
  else{  
    y = y-1; 
  } 
  if ((x+=1) > width) {
   x=0; 
  }
  
  if (mousePressed==true){  
    fill(50); 
    rect(width/2, height/2, width, height); 
    x=0;
    }
    
  
  }

buzoo YaBB Newbies Offline Posts: 14	Re: Odd behavior on Coordinates Reply #2 - Jul 24^th, 2005, 9:33pm Thanks. Hm, I don't know why the original code does not do a similar thing

mark hill

Re: Odd behavior on Coordinates
Reply #3 - Jul 24^th, 2005, 11:38pm

You have got nested conditionals

1st you test for the mouse button, and only when this is true do you then perform another conditional for x>width to determine whether x should be reset or not, but as you want to reset when the mouse is pushed it doesn't require any x test, as you'll be setting it to 0 regardless.

The X>width test needs to be outside of this reset function. When the x>width condition is satisifed you can do whatever you like, clear screen etc.

I hope this helps!

buzoo

Re: Odd behavior on Coordinates
Reply #4 - Jul 25^th, 2005, 5:07am

Yeah, I was a bit careless on what I wrote for what I originally aimed at. I wasn't too careful, and the result is the messy conditionals.
What really confused me at first was why the original program resets x not at 0, but at some values over. I assumed that "mousepressed" meant just one click. The longer I held the mouse button, the bigger x becomes for the 'reset' (Obvious now that I see it, hehe.)
Sorry for the confusion, thanks for the help!

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