topical media & game development
graphic-processing-site-examples-Basics-Form-BezierEllipse-BezierEllipse.pde / pde
Bezier Ellipse
By Ira Greenberg
Generates an ellipse using bezier() and
trig functions. Approximately every 1/2
second a new ellipse is plotted using
random values for control/anchor points.
// arrays to hold ellipse coordinate data
float[] px, py, cx, cy, cx2, cy2;
// global variable-points in ellipse
int pts = 4;
color controlPtCol = #222222;
color anchorPtCol = #BBBBBB;
void setup(){
size(200, 200);
smooth();
setEllipse(pts, 65, 65);
frameRate(1);
}
void draw(){
background(145);
drawEllipse();
setEllipse(int(random(3, 12)), random(-100, 150), random(-100, 150));
}
// draw ellipse with anchor/control points
void drawEllipse(){
strokeWeight(1.125);
stroke(255);
noFill();
// create ellipse
for (int i=0; i<pts; i++){
if (i==pts-1) {
bezier(px[i], py[i], cx[i], cy[i], cx2[i], cy2[i], px[0], py[0]);
}
else{
bezier(px[i], py[i], cx[i], cy[i], cx2[i], cy2[i], px[i+1], py[i+1]);
}
}
strokeWeight(.75);
stroke(0);
rectMode(CENTER);
// control handles and tangent lines
for ( int i=0; i< pts; i++){
if (i==pts-1){ // last loop iteration-close path
line(px[0], py[0], cx2[i], cy2[i]);
}
if (i>0){
line(px[i], py[i], cx2[i-1], cy2[i-1]);
}
line(px[i], py[i], cx[i], cy[i]);
}
for ( int i=0; i< pts; i++){
fill(controlPtCol);
noStroke();
//control handles
ellipse(cx[i], cy[i], 4, 4);
ellipse(cx2[i], cy2[i], 4, 4);
fill(anchorPtCol);
stroke(0);
//anchor points
rect(px[i], py[i], 5, 5);
}
}
// fill up arrays with ellipse coordinate data
void setEllipse(int points, float radius, float controlRadius){
pts = points;
px = new float[points];
py = new float[points];
cx = new float[points];
cy = new float[points];
cx2 = new float[points];
cy2 = new float[points];
float angle = 360.0/points;
float controlAngle1 = angle/3.0;
float controlAngle2 = controlAngle1*2.0;
for ( int i=0; i<points; i++){
px[i] = width/2+cos(radians(angle))*radius;
py[i] = height/2+sin(radians(angle))*radius;
cx[i] = width/2+cos(radians(angle+controlAngle1))*
controlRadius/cos(radians(controlAngle1));
cy[i] = height/2+sin(radians(angle+controlAngle1))*
controlRadius/cos(radians(controlAngle1));
cx2[i] = width/2+cos(radians(angle+controlAngle2))*
controlRadius/cos(radians(controlAngle1));
cy2[i] = height/2+sin(radians(angle+controlAngle2))*
controlRadius/cos(radians(controlAngle1));
//increment angle so trig functions keep chugging along
angle+=360.0/points;
}
}
(C) Æliens
20/2/2008
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