Non orthogonal collision

These days I been solving the problem of the non orthogonal collision.
I needed to find a system that would let some balls bounce inside an irregular shape, and finally I found it in the book Processing Creative Coding and Computational Art written by Ira Greenberg, where Ira explains how to deal when we want to know the boundaries of a irregular shape (At the same time, Ira explanation and code is based on Keith Peter”s Solution in Foundation Actionscript Animation: Making Things Move!).

The code he explains can be seen here:
http://processing.org/learning/topics/reflection2.html

I modified the code a little bit, because I wanted a ball bouncing inside an irregular surface instead on top of a irregular surface. Moreover, I adapt that code to openframeworks.
Here is a video with both programs running (First processing and then openframeworks):

non orthogonal collision from berio on Vimeo.

This is the processing code, that as I said, it is based on Ira Greenberg one:
There are 4 files:

bounceInsideShape.pde (Main document):

 
PVector velocity;
 
 float ptsx[] = {172, 209, 290, 380, 418, 409, 366, 303, 238, 190};
 float ptsy[] = {162, 96, 58, 83, 154, 218, 274, 296, 279, 228};
 Segment segments[] = new Segment[ptsx.length];
 float pt1X = 100;
 float pt1Y = 200;
 float pt2X = 200;
 float pt2Y = 100;
 float mx = (pt1X + pt2X) / 2;
 float my = (pt1Y + pt2Y) / 2;
 
 float rot = atan2((pt2Y-pt1Y), (pt2X-pt1X));
 
 Ball ball;
 
 void setup(){
 size(600, 350);
 smooth();
 ball = new Ball(220, 150, 3);
 velocity = new PVector(2, -4);
 
 for(int i=0; i if(i < ptsx.length-1){
 segments[i] = new Segment(ptsx[i], ptsy[i], ptsx[i+1], ptsy[i+1]);
 }else{
 segments[i] = new Segment(ptsx[i], ptsy[i], ptsx[0], ptsy[0]); 
 }
 }
 }
 
 void draw(){
 noStroke();
 fill(0, 15);
 rect(0, 0, width, height);
 
 ball.x += velocity.x;
 ball.y += velocity.y;
 checkWallCollision();
 
 // ************************
 // ** Check shape collision
 // ************************
 for(int i=0; i float deltax = ball.x - segments[i].x;
 float deltay = ball.y - segments[i].y;
 
 float cosine = cos(segments[i].rot);
 float sine = sin(segments[i].rot); 
 
 float groundXTemp = cosine * deltax + sine * deltay;
 float groundYTemp = cosine * deltay - sine * deltax;
 float velocityXTemp = cosine * velocity.x + sine * velocity.y;
 float velocityYTemp = cosine * velocity.y - sine * velocity.x;
 
 if(segments[i].isOnTop()){
 if(groundYTemp < ball.r && 
 ball.x > segments[i].x1 && 
 ball.x < segments[i].x2){
 
 groundYTemp = ball.r;
 velocityYTemp *= -1.0;
 } 
 }else{
 if(groundYTemp < ball.r && 
 ball.x < segments[i].x1 && 
 ball.x > segments[i].x2){
 
 groundYTemp = ball.r;
 velocityYTemp *= -1.0;
 } 
 }
 
 deltax = cosine * groundXTemp - sine * groundYTemp;
 deltay = cosine * groundYTemp + sine * groundXTemp;
 velocity.x = cosine * velocityXTemp - sine * velocityYTemp;
 velocity.y = cosine * velocityYTemp + sine * velocityXTemp;
 ball.x = segments[i].x + deltax; 
 ball.y = segments[i].y + deltay; 
 
 }
 
 stroke(255);
 for(int i=0; i line(segments[i].x1, segments[i].y1, segments[i].x2, segments[i].y2);
 }
 ellipse(ball.x, ball.y, ball.r*2, ball.r*2);
 }
 

Ball.pde (Class):

 
class Ball{
 float x, y, r;
 
 Ball() {
 }
 
 Ball(float x, float y, float r){
 this.x = x;
 this.y = y;
 this.r = r;
 }
 }
 

Segment.pde (Class):

 
class Segment{
 float x, y;
 float x1, y1, x2, y2;
 float rot;
 
 Segment(float _x1, float _y1, float _x2, float _y2){
 x1 = _x1;
 y1 = _y1;
 x2 = _x2;
 y2 = _y2;
 x = (x1 + x2) / 2;
 y = (y1 + y2) / 2; 
 rot = atan2((y2 - y1), (x2 - x1));
 }
 
 boolean isOnTop(){
 if(x2 > x1){
 return true;
 }else{
 return false;
 }
 } 
 }
 

checkWalls.pde (Functions):

 
void checkWallCollision(){
 if (ball.x > width-ball.r){
 ball.x = width-ball.r;
 velocity.x *= -1;
 // velocity.x *= damping;
 } 
 else if (ball.x < ball.r){
 ball.x = ball.r;
 velocity.x *= -1;
 // velocity.x *= damping;
 }
 else if(ball.y < ball.r){
 ball.y = ball.r;
 velocity.y *= -1;
 }
 else if(ball.y > height-ball.r){
 ball.y = height-ball.r;
 velocity.y *= -1;
 }
 }
 

Here you can download the openframeworks version: