Here's the JSFiddle: https://jsfiddle.net/y06jberm/1/
I intend to draw 3 randomly generated curves following the example from the second highest answer of this post: how to draw smooth curve through N points using javascript HTML5 canvas?
But the canvas only shows one curve at all time, despite the fact that I looped through the curves, and called .stroke after drawing each curve. The drawCurve function is somehow only called once, but I can't see why it is blocking. Can anyone spot any issue from this code? Thanks a million.
var curves = [];
var curX = 0;
for(var j = 0; j < 3; j++){
x = [];
for(var i = 0; i < 100; i++){
x.push(i*10);
x.push(100-Math.floor(Math.random()*100));
}
console.log(x);
curves.push(x);
}
var colors = ["red", "blue", "green"];
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
// console.log(ctx);
var tension = 1;
for(var i = 0; i < curves.length; i++){
ctx.stroke();
ctx.strokeStyle = colors[i];
console.log(colors[i]);
drawCurve(ctx, curves[i]);
}
// var inter = setInterval(moveCurve, 20);
var interval = setInterval(loadCurve, 200);
function moveCurve(){
curves[0].splice(0,2);
for(var i = 0; i < curves[0].length; i+=2){
curves[0][i] -= 10;
}
curves[0].push(990, Math.floor(Math.random()*100));
ctx.strokeStyle = colors[0];
ctx.clearRect(0,0,canvas.width, canvas.height);
drawCurve(ctx, curves[0]);
}
function drawCurve(ctx, ptsa, tension, isClosed, numOfSegments, showPoints) {
showPoints = showPoints ? showPoints : false;
showPoints = true;
// ctx.stroke();
ctx.beginPath();
drawLines(ctx, getCurvePoints(ptsa, tension, isClosed, numOfSegments));
// drawLines(ctx, ptsa);
// if (showPoints) {
// ctx.stroke();
// // ctx.beginPath();
// for(var i=0;i<ptsa.length-1;i+=2)
// ctx.rect(ptsa[i] - 2, ptsa[i+1] - 2, 4, 4);
// }
}
function getCurvePoints(pts, tension, isClosed, numOfSegments) {
// use input value if provided, or use a default value
tension = (typeof tension != 'undefined') ? tension : 0.5;
isClosed = isClosed ? isClosed : false;
numOfSegments = numOfSegments ? numOfSegments : 16;
var _pts = [], res = [], // clone array
x, y, // our x,y coords
t1x, t2x, t1y, t2y, // tension vectors
c1, c2, c3, c4, // cardinal points
st, t, i; // steps based on num. of segments
// clone array so we don't change the original
_pts = pts.slice(0);
// The algorithm require a previous and next point to the actual point array.
// Check if we will draw closed or open curve.
// If closed, copy end points to beginning and first points to end
// If open, duplicate first points to befinning, end points to end
if (isClosed) {
_pts.unshift(pts[pts.length - 1]);
_pts.unshift(pts[pts.length - 2]);
_pts.unshift(pts[pts.length - 1]);
_pts.unshift(pts[pts.length - 2]);
_pts.push(pts[0]);
_pts.push(pts[1]);
}
else {
_pts.unshift(pts[1]); //copy 1. point and insert at beginning
_pts.unshift(pts[0]);
_pts.push(pts[pts.length - 2]); //copy last point and append
_pts.push(pts[pts.length - 1]);
}
// ok, lets start..
// 1. loop goes through point array
// 2. loop goes through each segment between the 2 pts + 1e point before and after
for (i=2; i < (_pts.length - 4); i+=2) {
for (t=0; t <= numOfSegments; t++) {
// calc tension vectors
t1x = (_pts[i+2] - _pts[i-2]) * tension;
t2x = (_pts[i+4] - _pts[i]) * tension;
t1y = (_pts[i+3] - _pts[i-1]) * tension;
t2y = (_pts[i+5] - _pts[i+1]) * tension;
// calc step
st = t / numOfSegments;
// calc cardinals
c1 = 2 * Math.pow(st, 3) - 3 * Math.pow(st, 2) + 1;
c2 = -(2 * Math.pow(st, 3)) + 3 * Math.pow(st, 2);
c3 = Math.pow(st, 3) - 2 * Math.pow(st, 2) + st;
c4 = Math.pow(st, 3) - Math.pow(st, 2);
// calc x and y cords with common control vectors
x = c1 * _pts[i] + c2 * _pts[i+2] + c3 * t1x + c4 * t2x;
y = c1 * _pts[i+1] + c2 * _pts[i+3] + c3 * t1y + c4 * t2y;
//store points in array
res.push(x);
res.push(y);
}
}
return res;
}
function drawLines(ctx, pts) {
ctx.moveTo(pts[0], pts[1]);
for(i=2;i<pts.length-1;i+=2) ctx.lineTo(pts[i], pts[i+1]);
ctx.stroke();
ctx.closePath();
}
