Comments on: Exercise 9-8: Array of button objects

By: Daniel Shiffman

Daniel Shiffman — Tue, 18 Jan 2011 00:30:13 +0000

For circular buttons, you can use the distance function, i.e. if you know the x,y, and radius of the button you have:

float d = dist(mouseX,mouseY,x,y);
if (d < r) {
 // you are inside the button!
}

By: Jon

Jon — Thu, 06 Jan 2011 15:52:53 +0000

Hi,

Great exercise, but after I did it, i thought- how would you generate circular buttons? I started to try it but got stuck when I realised the x and y values are dependent on one another when you define a cartesian circle. Therefore I couldn’t define limits for the edge of the button.

Is there a way to do this simply using polar coordiantes? Or is it possible to define to variables such that they can describe a circle in the standard cartesian form? :
(x – a) ^ 2 + (y – b) ^ 2 = r ^ 2

If the way to do it is far more complicated than my current level of Processing knowledge then not to worry!

cheers

By: Daniel Shiffman

Daniel Shiffman — Tue, 09 Feb 2010 03:40:01 +0000

That’s exactly right. fill() affects the shapes drawn afterwards so you always want to make sure you call rect() (or whatever shape you want) after you set the rectangle’s color.

By: Maria Antônia

Maria Antônia — Mon, 08 Feb 2010 18:44:34 +0000

Hi!
Something weird happened here with my display function:

void display(){
rectMode(CORNER);
stroke(100);
rect(x,y,w,h); // when rect is here, the button that reacts is always the next button of the array…
if (on){
fill(175);
}else{
fill(0);
}
//rect(x,y,w,h); —-> when rect is here, the program works properly…
}

Is that any relation with the program flow, or is that a bug??