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Index › Programming Questions & Help › Programs › Can you tell me why
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Can you tell me why? (Read 467 times)
Sparragus
Can you tell me why?
Dec 1st, 2007, 10:43pm  
Hey everyone,

I'm currently learning Processing so I'm currently writing many programs just to practice. Recently  I tried to make a polygon drawing app but it doesn't seem to work. Can you spot the error? Thank you.

Quote:

//Geometry
int polygonSides = 3;
float radius = 20;

void setup()
{
 size(800,600);
 smooth();
 fill(255);
 stroke(255);  
 background(0);
}

void draw()
{
 pushMatrix();  
 translate(width/2,height/2);

 beginShape();
 for(int i=0; i<polygonSides; i++)
 {
   vertex(0,radius);
   rotate(TWO_PI/polygonSides);
 }
 endShape(CLOSE);

 popMatrix();
}
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didi
Re: Can you tell me why?
Reply #1 - Dec 2nd, 2007, 12:07am  
Quote from the beginShape() reference:
"
Transformations such as translate(), rotate(), and scale() do not work within beginShape()
"

So you'll have to calculate each vertex's cartesian coordinates using sin()...
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knutEinar
Re: Can you tell me why?
Reply #2 - Dec 7th, 2007, 7:20pm  
So here's a slightly modified code that should work ...

//Geometry
int polygonSides = 12;
float radius = 20;
float ypos, xpos;

void setup()
{
 size(200,200);
 smooth();
 fill(255);
 stroke(255);  
 noLoop();
 background(0);
}

void draw()
{
 // pushMatrix();  
 translate(width/2,height/2);

 beginShape();
 for(int i=1; i <= polygonSides; i++)
 {
   xpos = cos((TWO_PI*i/polygonSides);
   println("xpos :"+xpos);
   ypos = sin((TWO_PI*i/polygonSides);
    println("ypos :"+ypos);
   vertex(xpos*radius, ypos*radius);
 //  rotate(TWO_PI/polygonSides);
 println(i);
 }
 endShape(CLOSE);

//  popMatrix();
}
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