Glitchy rope physics(processing 2.2.1) - processing

Question

I made something to simulate a rope and it glitches out when the thing being held by the rope is under the thing holding the rope. This works when not in a for loop and its just one segment but i want to be able to simulate multiple segments.
code:
//Declaring variables
int linkCount = 3;
float Rotation = 0;
float R = radians(Rotation);
float x[] = new float[linkCount];
float y[] = new float[linkCount];
float xVel[] = new float[linkCount];
float yVel[] = new float[linkCount];
float ropeLength = 50;
float velMX;
float velMY;
float spring = 1;
void setup() {
size(1280, 500, P3D);
stroke(0);
fill(0);
}
void draw() {
background(255);
// Updating velocitys
for(int i=1; i < linkCount; i++) {
x[i] = x[i] + xVel[i];
y[i] = y[i] + yVel[i];
}
// The two lines below are not needed and will most likely will be used in the futre
velMX = pmouseX - mouseX;
velMY = pmouseY - mouseY;
// Setting the start of the rope to the mouse
x[0] = mouseX;
y[0] = mouseY;
// if(mousePressed) {
calcRopes();
// }
}
void calcRopes() {
for(int i = 1; i < linkCount; i++) {
// Getting a radian that points toward the last subrope
R = atan2(-(x[i] - x[i-1]), -(y[i] - x[i-1]));
// Drawing the rope
line(x[i], y[i], x[i - 1], y[i - 1]);
// If the segment is farther than the rope length it moves it inside the rope length based on the R radian
if(dist(x[i], y[i], x[i - 1], y[i - 1]) > ropeLength) {
x[i] = x[i] + ((dist(x[i], y[i], x[i - 1], y[i - 1]) - (ropeLength)) * sin(R));
y[i] = y[i] + ((dist(x[i], y[i], x[i - 1], y[i - 1]) - (ropeLength)) * cos(R));
// xVel[i] = ((dist(x[i], y[i], x[i-1], y[i-1]) - (ropeLength + 10)) * sin(R));
// yVel[i] = ((dist(x[i], y[i], x[i-1], y[i-1]) - (ropeLength + 10)) * cos(R));
}
}
}
How can I resolve this?

Answer 1

First of all: Don't use variables to set your screen size, processing 2.2.1 doesn't like that and Processing 3 doesn't even allow that.
Secondly:
line(x[i], y[i], x[i--], y[i--]);
Statements like this from calcRopes() will cause ArrayIndexOutOfBoundsException. Why are you using i-- for? Everytime you use that, i is decremented once. So starting with i=2, your value for i becomes -1 after the "line(x[i], y[i], x[i--], y[i--]);"
Edit:
This worked for me but I think it needs some adjustment still.
int linkCount = 10;
float Rotation = 0;
float R = radians(Rotation);
float x[] = new float[linkCount];
float y[] = new float[linkCount];
float xVel[] = new float[linkCount];
float yVel[] = new float[linkCount];
float ropeLength = 100;
float velMX;
float velMY;
float spring = 1;
void setup() {
size(1280, 500); //CHANGED THIS***********************
}
void draw() {
stroke(0);
fill(0);
background(255);
for (int i=0; i < linkCount; i++) {
x[i] = x[i] + xVel[i];
y[i] = y[i] + yVel[i];
}
velMX = pmouseX - mouseX;
velMY = pmouseY - mouseY;
x[1] = mouseX;
y[1] = mouseY;
// if(mousePressed) {
calcRopes();
// }
}
//REPLACED ALL i-- with i-1 (just to see if it works)***********************
void calcRopes() {
for (int i = 1; i < linkCount; i++) {
if (i<x.length && i<y.length) {
R = atan2(-(x[i] - mouseX), -(y[i] - mouseY));
line(x[i], y[i], x[i-1], y[i-1]);
if (dist(x[i], y[i], x[i - 1], y[i - 1]) > ropeLength) {
xVel[i] = ((dist(x[i], y[i], x[i-1], y[i-1]) - (ropeLength - 1)) * sin(R)) / spring;
yVel[i] = ((dist(x[i], y[i], x[i-1], y[i-1]) - (ropeLength - 1)) * cos(R)) / spring;
}
}
}
}

Answer 2

I found out this line:
R = atan2(-(x[i] - x[i-1]), -(y[i] - x[i-1]));
Had a error which made it miscalculate the radian
R = atan2(-(x[i] - x[i-1]), -(y[i] - y[i-1]));
Is what I wanted.
Im still having issues with making it look realistic but i can solve that myself.