Processing 1.0 - Processing Discourse - growing ellipse with for loop

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Index › Programming Questions & Help › Programs › growing ellipse with for loop

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growing ellipse with for loop (Read 563 times)

le_wuus

growing ellipse with for loop
May 30^th, 2008, 1:01pm

Hi! thanks for having a look at this!

I wrote a simple programm where an ellipse grows from the center untill it is 300 pxl wide. then it starts again.

I want do do the same thing but with an for loop because it seems I just don´t understand for loops right and I´m keen on learning them.

float a =50f;

void setup(){
size(400,400);
frameRate(30);
}

void draw(){
background(0);

a = a+2f;
fill(0, a);
float yo = map(a,0,300,255,0);
stroke(yo);
strokeWeight(20);
ellipse(200,200,a,a);

if (a>300){
a=50;
}
}

thank you for your help!

PhiLho

Re: growing ellipse with for loop
Reply #1 - May 30^th, 2008, 1:45pm

Interesting effect.
I rewrote a bit the snippet: note I like to use constants, it is easier to change several parameters at once, maintaining consistency. It is just a good habit to take.
Code:

final float MIN = 50f;
final float MAX = 300f;
float a = MIN;
 
void setup(){
size(400,400);
frameRate(30);
}
 
void draw(){
background(0);  
 
float alpha = int(map(a, MIN, MAX, 255, 0));
fill(#AABBCC, alpha);
stroke(alpha);
strokeWeight(20);
ellipse(width/2, height/2, a, a);
a = a+2f;
if (a > MAX){
  a = MIN;
}
}

I discovered map (and norm) with your code, useful functions...

for loop: since draw() already loops, it isn't really necessary here.
But we can use one to duplicate the figure and parametrize it:
Code:

final float MIN = 50f;
final float MAX = 200f;
float a = MIN;
int center;
 
void setup(){
size(800,200);
frameRate(30);
}
 
void draw(){
background(0);  
 
for (int i = 0; i < 4; i++)
{
float alpha = int(map(a, MIN, MAX, 255, 0));
fill(120, 180, i * 80, alpha);
stroke(alpha);
strokeWeight(6 * i);
ellipse((1 + 2 * i) * width/8, height/2, a, a);
a++;
if (a > MAX){
  a = MIN;
}
}
//delay(50);
}

le_wuus

Re: growing ellipse with for loop
Reply #2 - Jun 2^nd, 2008, 10:35pm

Hey Philo !
Thanks for your reply again!

Thats a good base to start with.
I´m doing a tangible music table sort of thing an
theese are my first visuals for the objects.
YEAH!

final float MIN = 0f;
final float MAX = 300f;
float a = MIN;
float b = MIN;
float c = MIN;
boolean circleAt100 = false;
boolean circleAt200 = false;

void setup(){
size(400,400);
frameRate(60);
}

void draw(){
background(0);

float alpha = int(map(a, MIN, MAX, 255, 0));
fill(0, alpha);
stroke(alpha);
strokeWeight(20);
ellipse(width/2, height/2, a, a);
a = a+2f;
if (a > MAX){
a = MIN;
}
if (a == 100){
circleAt100 = true;
}
if (circleAt100 == true){

float beta = int(map(b, MIN, MAX, 255, 0));
fill(0, beta);
stroke(beta);
strokeWeight(20);
ellipse(width/2, height/2, b, b);
b = b+2f;
if (b > MAX){
b = MIN;
}
}

if (a == 200){
circleAt200 = true;
}
if (circleAt200 == true){

float gamma = int(map(c, MIN, MAX, 255, 0));
fill(0, gamma);
stroke(gamma);
strokeWeight(20);
ellipse(width/2, height/2, c, c);
c = c+2f;
if (c > MAX){
c = MIN;
}
}

}

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