Creating Functions

Tutorials
1

Now you now know how to call functions, use variables, and create your own variables.

This is a companion discussion topic for the original entry at https://happycoding.io/tutorials/processing/creating-functions
2

I was trying to use the translate(x,y) function and it was behaving weirdly when placed inside a custom (user-defined) function of mine. It worked as expected only when I placed it inside the draw() function. Why does this happen? Do I need to always use it inside the draw() function only?

3

Hmm no, it shouldn’t matter if it’s inside draw() or inside a function that you call from draw(). Can you post some code that shows what you’re seeing?

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4 
class Star{
   float x,y,z;
   float sizeX,sizeY; 

   Star(){
    x=random(-width/2,width/2);
    y=random(-height/2,height/2);
    sizeX=5;
    sizeY=5;
   }
   
   void display(){
     translate(width/2,height/2);
     noStroke();
     ellipse(x,y,sizeX,sizeY);
   }
}


Star[] arrStars= new Star[1000];

void setup(){
  size(600,600);
  createStars();
  background(0);
}

void draw(){
  background(0);
  //translate(width/2,height/2);
  displayStars();
}

void createStars(){
   for(int i=0;i<arrStars.length;i++)
     arrStars[i]=new Star();
   return;
}

void displayStars(){
  //translate(width/2,height/2);
  for(int i=0;i<arrStars.length;i++){
    arrStars[i].display();
  }
}

I think I got why this was happening.
Each time draw() is called, everything (like the translation of origin because of translate() functions) is reset.
But if in one iteration of draw() if I call the translate(x,y) function many times(say 10 times) then it adds up each translate(x,y) call and translates the origin by corresponding cumulated sum times(10x, 10y).

5

Yep, that’s exactly right.

To get around this, you might look into using the pushMatrix() and popMatrix() functions:

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6

I tried using pushMatrix() and popMatrix(). It worked like magic.

1 Like