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What does the following code fragment print out?
int[] a = new int[10];
a[7]= 7;
int[]b = a;
println(b[7]);
b[7]= 8;
println(a[7]);
int c = 7;int d = c;
println(d);d = 8;
println(c);
7
87
7
The following sketch generates a
set of 100 moving circles and draws all chords linking theintersection points of all couples of intersecting circles.
/*
Structure 3
A surface filled with one hundred medium to small sized circles.
Each circle has a different size and direction, but moves at the same slow rate.
Display:
A. The instantaneous intersections of the circles
B. The aggregate intersections of the circles
Implemented by Casey Reas <http://groupc.net>
8 March 2004
Processing v.68 <http://processing.org>
modified by Pietro Polotti
28 March, 2006
Processing v.107 <http://processing.org>
*/
int numCircle = 100;
Circle[] circles = new Circle[numCircle];
void setup()
{
size(800, 600);
frameRate(50);
for(int i=0; i<numCircle; i++) {
circles[i] = new Circle(random(width),
(float)height/(float)numCircle * i,
int(random(2, 6))*10, random(-0.25, 0.25),
random(-0.25, 0.25), i);
}
ellipseMode(CENTER_RADIUS);
background(255);
}
void draw()
{
background(255);
stroke(0);
for(int i=0; i<numCircle; i++) {
circles[i].update();
}
for(int i=0; i<numCircle; i++) {
circles[i].move();
}
for(int i=0; i<numCircle; i++) {
circles[i].makepoint();
}
noFill();
}
class Circle
{
float x, y, r, r2, sp, ysp;
int id;
Circle( float px, float py, float pr, float psp, float pysp, int pid ) {
x = px;
y = py;
r = pr;
r2 = r*r;
id = pid;
sp = psp;
ysp = pysp;
}
void update() {
for(int i=0; i<numCircle; i++) {
if(i != id) {
intersect( this, circles[i] );
}
}
}
void makepoint() {
stroke(0);
point(x, y);
}
void move() {
x += sp;
y += ysp;
if(sp > 0) {
if(x > width+r) {
x = -r;
}
} else {
if(x < -r) {
x = width+r;
}
}
if(ysp > 0) {
if(y > height+r) {
y = -r;
}
} else {
if(y < -r) {
y = height+r;
}
}
}
}
void intersect( Circle cA, Circle cB )
{
float dx = cA.x - cB.x;
float dy = cA.y - cB.y;
float d2 = dx*dx + dy*dy;
float d = sqrt( d2 );
if ( d>cA.r+cB.r || d<abs(cA.r-cB.r) ) {
return; // no solution
}
// calculate the two intersections between the two circles cA and cB, //
// whose coordinates are (paX, paY) and (pbX, pbY), respectively. //
stroke(255-dist(paX, paY, pbX, pbY)*4);
line(paX, paY, pbX, pbY);
}
/*
Structure 3
A surface filled with one hundred medium to small sized circles.
Each circle has a different size and direction, but moves at the same slow rate.
Display:
A. The instantaneous intersections of the circles
B. The aggregate intersections of the circles
Implemented by Casey Reas <http://groupc.net>
8 March 2004
Processing v.68 <http://processing.org>
modified by Pietro Polotti
28 March, 2006
Processing v.107 <http://processing.org>
*/
int numCircle = 100;
Circle[] circles = new Circle[numCircle];
void setup()
{
size(800, 600);
frameRate(50);
for(int i=0; i<numCircle; i++) {
circles[i] = new Circle(random(width),
(float)height/(float)numCircle * i,
int(random(2, 6))*10, random(-0.25, 0.25),
random(-0.25, 0.25), i);
}
ellipseMode(CENTER_RADIUS);
background(255);
}
void draw()
{
background(255);
stroke(0);
for(int i=0; i<numCircle; i++) {
circles[i].update();
}
for(int i=0; i<numCircle; i++) {
circles[i].move();
}
for(int i=0; i<numCircle; i++) {
circles[i].makepoint();
}
noFill();
}
class Circle
{
float x, y, r, r2, sp, ysp;
int id;
Circle( float px, float py, float pr, float psp, float pysp, int pid ) {
x = px;
y = py;
r = pr;
r2 = r*r;
id = pid;
sp = psp;
ysp = pysp;
}
void update() {
for(int i=0; i<numCircle; i++) {
if(i != id) {
intersect( this, circles[i] );
}
}
}
void makepoint() {
stroke(0);
point(x, y);
}
void move() {
x += sp;
y += ysp;
if(sp > 0) {
if(x > width+r) {
x = -r;
}
} else {
if(x < -r) {
x = width+r;
}
}
if(ysp > 0) {
if(y > height+r) {
y = -r;
}
} else {
if(y < -r) {
y = height+r;
}
}
}
}
void intersect( Circle cA, Circle cB )
{
float dx = cA.x - cB.x;
float dy = cA.y - cB.y;
float d2 = dx*dx + dy*dy;
float d = sqrt( d2 );
if ( d>cA.r+cB.r || d<abs(cA.r-cB.r) ) {
return; // no solution
}
float a = (cA.r2 - cB.r2 + d2) / (2*d);
float h = sqrt( cA.r2 - a*a );
float x2 = cA.x + a*(cB.x - cA.x)/d;
float y2 = cA.y + a*(cB.y - cA.y)/d;
float paX = x2 + h*(cB.y - cA.y)/d;
float paY = y2 - h*(cB.x - cA.x)/d;
float pbX = x2 - h*(cB.y - cA.y)/d;
float pbY = y2 + h*(cB.x - cA.x)/d;
stroke(255-dist(paX, paY, pbX, pbY)*4);
line(paX, paY, pbX, pbY);
}
Make the sketch of interactive. For example, make the circle displacement dependent on the horizontal positionof the mouse.
/*
Structure 3
A surface filled with one hundred medium to small sized circles.
Each circle has a different size and direction, but moves at the same slow rate.
Display:
A. The instantaneous intersections of the circles
B. The aggregate intersections of the circles
Implemented by Casey Reas <http://groupc.net>
8 March 2004
Processing v.68 <http://processing.org>
modified by Pietro Polotti
28 March, 2006
Processing v.107 <http://processing.org>
*/
int numCircle = 100;
Circle[] circles = new Circle[numCircle];
void setup()
{
size(800, 600);
frameRate(50);
for(int i=0; i<numCircle; i++) {
circles[i] = new Circle(random(width),
(float)height/(float)numCircle * i,
int(random(2, 6))*10, random(-0.25, 0.25),
random(-0.25, 0.25), i);
}
ellipseMode(CENTER_RADIUS);
background(255);
}
void draw()
{
background(255);
stroke(0);
if(mousePressed){
for(int i=0; i<numCircle; i++) {
circles[i].sp = mouseX*random(-5, 5)/width;
}
}
for(int i=0; i<numCircle; i++) {
circles[i].update();
}
for(int i=0; i<numCircle; i++) {
circles[i].move();
}
for(int i=0; i<numCircle; i++) {
circles[i].makepoint();
}
noFill();
}
class Circle
{
float x, y, r, r2, sp, ysp;
int id;
Circle( float px, float py, float pr, float psp, float pysp, int pid ) {
x = px;
y = py;
r = pr;
r2 = r*r;
id = pid;
sp = psp;
ysp = pysp;
}
void update() {
for(int i=0; i<numCircle; i++) {
if(i != id) {
intersect( this, circles[i] );
}
}
}
void makepoint() {
stroke(0);
point(x, y);
}
void move() {
x += sp;
y += ysp;
if(sp > 0) {
if(x > width+r) {
x = -r;
}
} else {
if(x < -r) {
x = width+r;
}
}
if(ysp > 0) {
if(y > height+r) {
y = -r;
}
} else {
if(y < -r) {
y = height+r;
}
}
}
}
void intersect( Circle cA, Circle cB )
{
float dx = cA.x - cB.x;
float dy = cA.y - cB.y;
float d2 = dx*dx + dy*dy;
float d = sqrt( d2 );
if ( d>cA.r+cB.r || d<abs(cA.r-cB.r) ) {
return; // no solution
}
float a = (cA.r2 - cB.r2 + d2) / (2*d);
float h = sqrt( cA.r2 - a*a );
float x2 = cA.x + a*(cB.x - cA.x)/d;
float y2 = cA.y + a*(cB.y - cA.y)/d;
float paX = x2 + h*(cB.y - cA.y)/d;
float paY = y2 - h*(cB.x - cA.x)/d;
float pbX = x2 - h*(cB.y - cA.y)/d;
float pbY = y2 + h*(cB.x - cA.x)/d;
stroke(255-dist(paX, paY, pbX, pbY)*4);
line(paX, paY, pbX, pbY);
}
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