Using Scale() with Draw()

Programming Questions

ofeyrpf

in Programming Questions • 1 years ago

Why does the following not work to grow an ellipse?

void setup() {
size(200, 200);
smooth();
}
void draw() {
background(255);
scale(1.2, 1.2);
ellipse(20, 20, 20, 20);
}

Any help would be greatly appreciated,

Thanks,

Shane

Replies(7)

tfguy44

Re: Using Scale() with Draw()

1 years ago

Works fine for me. Look:

void setup() {
size(200, 200);
smooth();
}
void draw() {
background(255);
ellipse(20, 20, 20, 20);
scale(1.2, 1.2);
ellipse(60, 20, 20, 20);
}

PhiLho

Re: Using Scale() with Draw()

1 years ago

scale, translate, rotate are reset on each draw() call. Use a global variable and change the value there, using the value in the scale() call.

ofeyrpf

Re: Using Scale() with Draw()

1 years ago

Great I got it now, with

float i;

void setup() {
size(200, 200);
smooth();
}
void draw() {
background(255);
scale(i, i);
ellipse(20, 20, 20, 20);
i += 0.1;
}

This is exactly what I was trying to do and it works for rotate and translate too.

Thanks,

Shane

tech37

Re: Using Scale() with Draw()

1 years ago

@ofeyrpf

I try this code. It only grow, grow, grow, ...gone... I replace this line i +=0.1 to i+=0.01 The circle grow slow, slow, slow and gone... I wonder how to repeat again ...

PhiLho

Re: Using Scale() with Draw()

1 years ago

When i reaches a value (eg. width / 2), reset it to the initial value.
Or replace the constant with a variable, and when reaching max or min, change the sign of the variable.

tech37

Thank phi.lho.... Grr I wonder why I did not figure this out... And I also try to place a for() loop in this code, and I only got : A big blank white screen. I am lost ??? I wonder why the circle simply did not draw ? A delay() , forget it, I got a gray screen and freeze program ( have to use ALT-Delete to un-freeze it ) And a for() within my loop, forget that one either, it froze also, still blank but a white.

Any idea ? I am out of it...

Here the code:

float i;
void setup()
{
size(500, 500);
smooth();
i=0;
}
void draw()
{
background(255);
movecircle();
i=i+0.1;
if (i>=30)
{
i=0;
}
}
void movecircle()
{
scale(i, i);
ellipse(20, 20, 20, 20);
}
// Not working code
float i;
void setup()
{
size(500, 500);
smooth();
i=0;
}
void draw()
{
for (int j=0;j<300;j++)
{
background(255);
movecircle();
i=i+0.1;
}

}
void movecircle()
{
scale(i, i);
ellipse(20, 20, 20, 20);
}

tech37

Re: Using Scale() with Draw()

1 years ago

I did it ! I wrote a code to do : a small dark green circle getting bigger and bigger, and than going smaller, smaller, and than again, again , again... I use a variable call "flag" to control which way, and a if() with && <-- that mean AND to check the "flag" Cool heh ! ( I just think of an animation of an orbiting planet ... Mmm )

But I still don't understand why the for() loop in my last posting did not work, I even try to fill with color, But NOOO , still not working.

Anyway, here the code of a small to big and big to small.

float i;
int flag;
void setup()
{
size(500, 500);
smooth();
// init i and flag
i=0;
flag=0;
}
void draw()
{
background(255);
movecircle();
// check if going bigger
if (i>=0 && flag==0)
{
i=i+0.1;
    // check until 30 and change flag
    if (i>=30 && flag==0)
    {
      flag=1;
    }
}
// check if going smaller
if (i>=0 && flag==1)
{
i=i-0.1;
    // check until 0.1 ( near zero ) and change flag
    if (i<=0.1 && flag==1)
    {
      flag=0;
    }
}


}
void movecircle()
{
// the circle picture
fill(255);
strokeWeight(2);
stroke(21,90,2); // color dark green
scale(i, i);
ellipse(20, 20, 20, 20);
}

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