# PolarToCartesian

### byDaniel Shiffman

Convert a polar coordinate (r,theta) to cartesian (x,y). The calculations are x=r*cos(theta) and y=r*sin(theta).

``````/**
* Polar to Cartesian
* by Daniel Shiffman.
*
* Convert a polar coordinate (r,theta) to cartesian (x,y).
* The calculations are x=r*cos(theta) and y=r*sin(theta).
*/

float r;

// Angle and angular velocity, accleration
float theta;
float theta_vel;
float theta_acc;

void setup() {
size(640, 360);

// Initialize all values
r = height * 0.45;
theta = 0;
theta_vel = 0;
theta_acc = 0.0001;
}

void draw() {

background(0);

// Translate the origin point to the center of the screen
translate(width/2, height/2);

// Convert polar to cartesian
float x = r * cos(theta);
float y = r * sin(theta);

// Draw the ellipse at the cartesian coordinate
ellipseMode(CENTER);
noStroke();
fill(200);
ellipse(x, y, 32, 32);

// Apply acceleration and velocity to angle
theta_vel += theta_acc;
theta += theta_vel;

}
``````

This example is for Processing 4+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.