Flat Sided Circle Problem

Programming Questions

tehquickn..

in Programming Questions • 1 year ago

I am trying to do a simple code to draw a multisided circle using the code below. For some reason, a flat side starts to form in my circle and I am not sure why. It is pretty obvious when the number of sides is 19.

Any thoughts?

void setup() {
int sides = 18;
size(800,800);
drawCylinder(400,400,sides,200);
}
void drawCylinder(int orginX, int orginY, int sides, float r) {
float angle = 360 / sides;
beginShape();
for(int i = 0; i < sides; i++) {
float x = (cos( radians ( i * angle ) ) * r)+ orginX;
float y = (sin( radians ( i * angle ) ) * r)+ orginY;
vertex( x,y );
print ("i: "+i+" "+x+","+y+"\n");
}
endShape(CLOSE);
}

Replies(3)

Ale_

Re: Flat Sided Circle Problem

1 year ago

You only have to fix the iteration: (i<= sides) instead of (i<sides).

And a suggestion:

(angle = TWO_PI/sides) instead of (360/sides). This way you don´t have to use radians() afterwards.
;-)

Ale · http://60rpm.tv/i

tehquickn..

Re: Flat Sided Circle Problem

1 year ago

Interesting. You bring up a great point. For some reason:

angle = 360 / sides;
x = cos ( radians ( i * angle ) ) * r;

is not the same as your suggestion:

angle = TWO_PI / sides;
x = cos ( i * angle ) * r;

The first example will give me 1 extra side (so 20 sides when I requested only 19 hence the flat spot and the need for i<=sides). But I cannot explain the logic.

After Further investigation, I cant explain the following math through processing. Even though the two statements below should be totally equal. Processing gives different results.

float angle = TWO_PI / 19; DOES NOT EQUAL float angle = radians(360 / sides);

angle = .33069 angle = .31415

Can anyone explain why?

kooogy

Re: Flat Sided Circle Problem

1 year ago

> 360 / sides

probably won't give you the answer you're expecting, especially if sides is 19 - you're dividing an int by and int so you'll get an int answer, ie it'll round down.