Processing 1.0 - Processing Discourse - How to draw circle from points?

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Index › Programming Questions & Help › Syntax Questions › How to draw circle from points

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How to draw circle from points? (Read 1013 times)

sonomute YaBB Newbies Offline Posts: 20	How to draw circle from points? Feb 24^th, 2009, 2:21pm Hello! Can somebody give a hand with this? I know it's almost pre mathematics, and this is why i'm asking, not good in it... If i will place enough points around central point on the same direction each, they will create a circle. how can i calculate coordinates for every next point? thanx!

vicente

Re: How to draw circle from points?
Reply #1 - Feb 24^th, 2009, 3:08pm

This is trigonometry, circular functions, sine, cosine, tangent.

http://en.wikipedia.org/wiki/Trigonometry

Basically you should use the sine of a given angle as Y coordinate and the cosine of the same angle as X coordinate and then increment the angle. You may want to use a factor (multiplying both numbers by it) to control the circle size.
Beware that trigonometrical functions expect the angle as radians, you can convert using radians() function.

some thing like:

int x;
void draw(){
if(x<360){x++;}
pushMatrix();
translate(width/2,height/2);// bring zero point to the center

stroke(0);

point (sin(radians(x))*50,cos(radians(x))*50);
point (sin(radians(x))*25,cos(radians(x))*25);

stroke(255);

point (sin(radians(x))*50,cos(radians(x))*25);//<ellipse
popMatrix();

}

sonomute

Re: How to draw circle from points?
Reply #2 - Feb 24^th, 2009, 7:40pm

Hi! Thank you for answer!
Actually i'm trying to understand how to rotate svg shape around it's center...

can you check my code please?

PShape bot;

void setup()
{
size(500,500);
smooth();
frameRate(30);
bot = loadShape("pum.svg");
}

void draw()
{
background(200);

translate(width/2, height/2);

shape(bot, 0, 0,100,100);
bot.rotate(radians(1));

}

if i'm changing pshape mode to CENTER it is still rotating around left top corner...

how can i implement all those sin and cos thingies to to translate 0,0 point of shape so it will move around center of shape...

« Last Edit: Feb 24^th, 2009, 9:25pm by sonomute »

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