Arctangent
/**
* Arctangent.
*
* Move the mouse to change the direction of the eyes.
* The atan2() function computes the angle from each eye to the cursor.
*/
struct Eye {
int x, y, size;
float angle = 0.0;
Eye(int tx, int ty, int ts) : x(tx), y(ty), size(ts) {}
void update(int mx, int my) {
angle = atan2(my - y, mx - x);
}
void display() {
pushMatrix();
translate(x, y);
fill(255); noStroke();
ellipse(0, 0, size, size);
rotate(angle);
fill(153, 204, 0);
ellipse(size/4, 0, size/2, size/2);
popMatrix();
}
};
Eye e1(250, 16, 120);
Eye e2(164, 185, 80);
Eye e3(420, 230, 220);
void setup() {
size(640, 360);
noStroke();
}
void draw() {
background(102);
e1.update(mouseX, mouseY); e1.display();
e2.update(mouseX, mouseY); e2.display();
e3.update(mouseX, mouseY); e3.display();
}