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Trouble with basic 2d collision detection

[9 Replies]
- 02-Mar-2012 10:37 AM
- Forum: Programming Questions
SOLVED - See my last reply for details on how i got the below problem to work.

So i would like the non player circles to change colour whenever they overlap, but i fear i haven't implemented the collide() function properly in the CompBall class.
This is what happens below:
-when circles 0 & 1 overlap, they both do not change colour ( fail)

-when circles 0 & 2 overlap, only circle 0 changes colour ( fail)

-when circles 1 & 2 overlap, they both change colour ( pass)

could any one give me a hand?

thanks :)

Main Class:
CompBall[] cBalls;

PlayerBall player;

//---------------------------------------------------------------------------

void setup() {

size(800, 800);

cBalls = new CompBall[3];

for (int i = 0; i < cBalls.length; i++) {

cBalls[i] = new CompBall(random(500), random(500), 100, 100, i, cBalls);

}

player = new PlayerBall(random(500), random(500), 100, 100);

smooth();

}

//---------------------------------------------------------------------------

void draw() {

stroke(0);

println(frameRate);

background(0);

for (int i = 0; i < cBalls.length; i++) {

cBalls[i].collide();

cBalls[i].move(player.x, player.y, player.repel);

cBalls[i].display();

}

player.move(mouseX, mouseY);

for (int i = 0; i < cBalls.length; i++) {

if (dist(cBalls[i].x, cBalls[i].y, mouseX, mouseY) < 4) {

player.shrink();

}

}

player.display();

if (player.w < 20) {

noLoop();

}

}

CompBall Class:
class CompBall {

float x, y, w, h, speed, gravity;

color c;

int id;

CompBall[] cba;

//---------------------------------------------------------------------------

CompBall(float tx, float ty, float tw, float th, int tempID, CompBall[] tempCBA) {

x = tx;

y = ty;

w = tw;

h = th;

c = color(0, 200, 0);

speed = 2;

id = tempID;

cba = tempCBA;

}

//---------------------------------------------------------------------------

void move(float mx, float my, boolean repel) {

// Distance between X & Y co-ordinates

float diffX = mx - x;

float diffY = my - y;

// Length between the 2 points (pythag)

float len = sqrt((diffX * diffX) + (diffY * diffY));

// Catch any divide by zero situations

if (len != 0)

{

// Work out 1 unit of travel for X & Y

diffX /= len;

diffY /= len;

}

// Move the 1 unit of length by speed

diffX *= speed;

diffY *= speed;

if (!repel) {

// Change the X & Y of the object

x += diffX;

y += diffY;

}

else {

// Change the X & Y of the object

x -= diffX;

y -= diffY;

}

// Ensure the balls don't disappear off the edge

x = constrain(x, w/2, width-w/2);

y = constrain(y, w/2, height-w/2);

}

//---------------------------------------------------------------------------

void collide() {

for (int i = id + 1; i < cba.length; i++) {

float dx = cba[i].x - x;

float dy = cba[i].y - y;

float distance = sqrt(dx*dx + dy*dy);

if ( distance < cba[i].w ) {

c = color(0, 0, 200);

cba[i].c = color(0, 0, 200);

}

else {

c = color(0, 200, 0);

cba[i].c = color(0, 200, 0);

}

}

}

//---------------------------------------------------------------------------

void display() {

ellipseMode(CENTER);

textMode(CENTER);

noStroke();

for (float i = w; i > 0; i-=4) {

fill(c, i);

ellipse(x, y, i, i);

fill(0);

text(id, x, y);

}

}

}
PlayerBall Class:
class PlayerBall {

float x, y, w, h, speed;

color c;

boolean repel;

//---------------------------------------------------------------------------

PlayerBall(float tx, float ty, float tw, float th) {

x = tx;

y = ty;

w = tw;

h = th;

c = color(100, 0, 0);

speed = 1;

}

//---------------------------------------------------------------------------

void move(float mx, float my) {

x = mx;

y = my;

x = constrain(x,w/2,width-w/2);

y = constrain(y,w/2,height-w/2);

}

//---------------------------------------------------------------------------

void shrink() {

w -= 0.5;

h -= 0.5;

}

//---------------------------------------------------------------------------

void display() {

ellipseMode(CENTER);

noStroke();

if (mousePressed) {

for (float i = w; i > 0; i-=4) {

fill(255-i, i);

ellipse(x, y, i, i);

}

repel = !repel;

}

else {

for (float i = w; i > 0; i-=4) {

fill(255-i, 0, 0, i);

ellipse(x, y, i, i);

}

}

}

}

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