pushMatrix error

Programming Questions

oscar_co

in Programming Questions • 9 months ago

I am currently attempting to get a star-shaped geometry to rotate around its center, but to no avail!

I am either continually met with 'pushMatrix() cannot use push more than 32 times', or, when that is removed, I end up with 'StackOverflowError:This sketch is attempting too much recursion'

I'm afraid I am very new to processing so I'm struggling to find a solution, even after many trawls through the tinter!

Any help gratefully received!

The code:

//VARIABLES

float angle;

//SETUP

void setup( )

{

size(500, 500);

background(55);

smooth();

fill(102,102,102,50);

stroke (255);

strokeWeight (2);

//DRAW STAR

star(5, 250, 250, 450, 450, -PI / 2.0, 0.50);

}

void star(int n, float cx, float cy, float w, float h,

float startAngle, float proportion)

{

float angle = TWO_PI/ (2 *n);

float dw;

float dh;

w = w / 2.0;

h = h / 2.0;

beginShape();

for (int i = 0; i < 2 * n; i++)

{

dw = w;

dh = h;

if (i % 2 == 1)

{

dw = w * proportion;

dh = h * proportion;

}

vertex(cx + dw * cos(startAngle + angle * i),

cy + dh * sin(startAngle + angle * i));

}

//ROTATE

{

pushMatrix();

endShape(CLOSE);

rectMode(CENTER);

translate(250,250);

rotate(radians (45));

star(5, 250, 250, 450, 450, -PI / 2.0, 0.50);

popMatrix();

}

Replies(1)

asimes

Re: pushMatrix error

9 months ago

It looks like that will cause infinite recursion (star() calls itself forever). You actually don't need recursion for this problem, here is a solution:

int step;
float angle, rad1, rad2;
void setup() {
size(600, 600);
step = 10;
rad1 = 150.0;
rad2 = 250.0;
}
void draw() {
background(255);
translate(width/2, height/2);
beginShape();
for (int i = 0; i < step; i++) {
float whichRad = (i%2 == 0)?rad1:rad2;
angle += TWO_PI/step;
float x = cos(angle)*whichRad;
float y = sin(angle)*whichRad;
vertex(x, y);
}
endShape(CLOSE);
angle += TWO_PI/360;
}

This tutorial is good for explaining the cos() and sin(): http://processing.org/learning/trig/