why is it not a perfect circle?

Programming Questions

nootropic..

why is it not a perfect circle?

in Programming Questions • 2 years ago

i don't understan why it is not a perfect circle!!

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float inner_radius = 80f, outer_radius = 160f;
int numpoint = 30;
void setup() {
size(500, 500);
smooth();
}
void draw() {
background(0);
translate(width/2, height/2);
float k = 6;
float c[], s[];
float theta=0, dt;
noFill();
stroke(200);
c = new float[numpoint];
s = new float[numpoint];
stroke(200);
noFill();
dt=TWO_PI/(k*(numpoint));
for(int spicchi=0; spicchi<k; spicchi++) {
println( degrees(theta) );
for(int i=0; i<numpoint; i++) {
c[i] = cos(theta);
s[i] = sin(theta);
theta += dt;
}
beginShape();
for(int i=0; i<numpoint; i++) {
vertex(c[i]*inner_radius, s[i]*inner_radius);
}
for(int i=numpoint-1; i>0; i--) {
vertex(c[i]*outer_radius, s[i]*outer_radius);
}
vertex(c[0]*inner_radius, s[0]*inner_radius);
endShape();
}
println( degrees(theta) );
noLoop();
}

Replies(4)

cedrickie..

Re: why is it not a perfect circle?

2 years ago

what is not perfect? it is at least round as it should be.
how is it supposed to look like ?

nootropic..

Re: why is it not a perfect circle?

2 years ago

it is not closed!

this is what i want!

[edit]

i've done with a really dirty hack

Copy code

beginShape();
for(int i=0; i<numpoint; i++) {
vertex(c[i]*inner_radius, s[i]*inner_radius);
}
vertex(cos(theta+dt)*inner_radius, sin(theta+dt)*inner_radius);
vertex(cos(theta+dt)*outer_radius, sin(theta+dt)*outer_radius);
for(int i=numpoint-1; i>0; i--) {
vertex(c[i]*outer_radius, s[i]*outer_radius);
}
endShape();

but if i put lower sampling point for each slice ( numpoint=5 ) it get some bad errors!

i don't like this solutions at all!

amnon.owed

Re: why is it not a perfect circle?

2 years ago

I tried to disassemble your code, but ended up with some kind of weird zoopraxiscope!

There's some stuff going on you probably don't need. If you just want the shape, of course there are many ways to make it, for example arcs or curveVertices. It depends on your end-goal. Perhaps going back to basics will provice some clarity with regard to accurate sin-cos rotation.

Code example:

Copy code

boolean linesOnly;
void mouseClicked() { linesOnly = !linesOnly; } // click the mouse to toggle
float inner_radius = 80;
float outer_radius = 160;
int numpoints;
void setup() {
size(500,500);
smooth();
noFill();
strokeWeight(2);
}
void draw() {
background(0);
translate(width/2, height/2);
numpoints = 3 + mouseX/25;
stroke(200);
if (linesOnly) { beginShape(LINES); } else { beginShape(QUAD_STRIP); }
for(int i=0; i<numpoints+1; i++) {
vertex(sin(radians(i*360/numpoints))*inner_radius, cos(radians(i*360/numpoints))*inner_radius);
vertex(sin(radians(i*360/numpoints))*outer_radius, cos(radians(i*360/numpoints))*outer_radius);
}
endShape();
stroke(0,200,0);
ellipse(0,0,inner_radius*2,inner_radius*2);
ellipse(0,0,outer_radius*2,outer_radius*2);
}

nootropic..

Re: why is it not a perfect circle?

2 years ago

hei :)

weird zoopraxiscope is the Path.. ;)

well, i'm using processing to prototype, you know, i wanto to learn pure opengl and all others setups that proceesing hopefully bypass when scretching, so i'm tring not to use PApplet arcs and curves at all

[and, honestly i love have trouble with trigonometry and good old plain vertex]

bytheway, i wanto to do a color wheel like adobe illustrator "colour harmony" panel i don't know if you've got in mind (and actually i'musing the little hacks i posted and now doing harmony rule system)

so i need to do a slices with different colours and with your QUAD_STRIP technicque is not possible

i think the problem is that in a really strange&weird way i skip a pass of theta+dt and... i don't know,

but if you have solutions or something that could be put in let me know!

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