What is the initial value of X in this code from the book?

appleliver

Hi, I'm new to processing and I have a small question about Example 5-8 : Easing Does It in the second eddition of the getting started with processing book.

Here is the code:

    float x;
    float easing = 1;

    void setup(){
    size(544,416);
    }

    void draw(){
      float targetX = mouseX;           
      x += (targetX - x)*easing;          
      ellipse(x, 40, 12, 12);            
      println(targetX + " : " + x); 
    }

My question is about the value of x. From my understanding, the value of (targetX - x)*easing is added onto the variable x, but in that formula, x is being taken away. What exactly is the initial value of x, how is this being calculated?

Chrisir

you can find out by inserting println(x); into setup()

Chrisir

apart from that, easing should be <1 and background should be used:

float x;
float easing = .04;

void setup() {
  size(544, 416);
}

void draw() {
  background(0); 
  float targetX = mouseX;           
  x += (targetX - x)*easing;          
  ellipse(x, 40, 12, 12);            
  println(targetX + " : " + x);
}

GoToLoop

https://forum.Processing.org/two/discussion/18404/processing-code-doesn-t-work-in-p5#Item_5
http://studio.SketchPad.cc/sp/pad/view/ro.9XkJm3bjTAxB2/latest

appleliver

Thank you very much, sorry I feel quite stupid (that should be really obvious, I guess)!

koogs

2nd time this has been asked this week, so no, not obvious.

I'd always recommend defining variables with an explicit value for clarity.

jeremydouglass

Processing uses Java's default initializations if they are not specified (e.g. int 0; String null, boolean false) for global variables -- although clarity in your code is better. The compiler sets float x to 0.0f

https://forum.processing.org/two/discussion/comment/76061/#Comment_76061

http://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html

koogs

but that relies on you knowing the processing is java and then knowing the java defaults 8)

actually, that link above is to a third person asking the same question. which makes me think this is all an assignment.