Ball - line intersection - Processing Forum

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corvaccio

Ball - line intersection

in Programming Questions • 1 year ago

Hi guys,

I'm trying to write a method that can tell if a ball intersect a line drawn with the mouse. The ball is a simple ellipse() and the line...a line(). Thanks!

Replies(6)

allonestr..

Re: Ball - line intersection

1 year ago

Post what you've done so far.

corvaccio

Re: Ball - line intersection

1 year ago

Mover mover;
Ball ball;
void setup(){
size(400, 400);
mover = new Mover (0,0,0,0);
ball = new Ball();
smooth();
}
void draw(){
ball.update();
ball.checkEdges();
ball.display();
}
void mousePressed(){
mover.x = mouseX;
mover.y = mouseY;
}
void mouseReleased(){
background (255);
mover.x1 = mouseX;
mover.y1 = mouseY;
mover.display();
}
class Ball{
// Our object has two PVectors: location and velocity
PVector location;
PVector velocity;
PVector acceleration;
float topspeed;
Ball() {
location = new PVector(width/2, height/2);
velocity = new PVector(0,0);
acceleration = new PVector(-0.001,0.01);
topspeed = 10;
}
void update() {
// Motion 101: Locations changes by velocity.
velocity.add(acceleration);
velocity.limit(topspeed);
location.add(velocity);
}
void display() {
stroke(0);
fill(175);
ellipse(location.x,location.y,16,16);
}
void checkEdges() {
if ((location.x > width) || (location.x < 0)){
velocity.x = velocity.x * -1;
}
if ((location.y > width) || (location.y < 0)){
velocity.y = velocity.y * -1;
}
}
}
class Mover{
float x,y,x1,y1;
Mover(float tempX,float tempY,float tempX1,float tempY1){
x = tempX;
y = tempY;
x1 = tempX1;
y1 = tempY1;
}
void display(){
stroke(10);
line(x,y,x1,y1);
}
}

I need to calculate the angle of the line, the collsion with the ball and then reverse the speed of the ball accordin with the angle of the line...or something like that...

allonestr..

Re: Ball - line intersection

1 year ago

A pretty standard way of doing it is to rotate the collision detection and resolution, then rotate it back.

You know how to collide with a vertical or horizontal line, so you rotate the line so that it's horizontal, rotate the ball's velocity and position relative to the line by the same angle; do the collision; rotate everything back by the same angle.

See my own question from a while ago http://forum.processing.org/topic/collision-on-angled-line-generalisation as an example.

corvaccio

Re: Ball - line intersection

1 year ago

Wow that's a solution (push and pop matrix?). Now I've to figure out how to detect the collision and how to calculate the angle of rotation. Any guess?

allonestr..

Re: Ball - line intersection

1 year ago

look at sections 3 and 4 of the Ball class

corvaccio

Re: Re: Ball - line intersection

1 year ago

Cool man i will give it a try :D Thank you!!!

P.s. what do you think about 2Dbox? Will it be easier if i use it?

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