Here is the code for drawing curve from N points:


// move to the first point
ctx.moveTo(points[0].x, points[0].y);

for (i = 1; i < points.length - 2; i ++)
{
var xc = (points[i].x + points[i + 1].x) / 2;
var yc = (points[i].y + points[i + 1].y) / 2;
ctx.quadraticCurveTo(points[i].x, points[i].y, xc, yc);
}

// curve through the last two points
ctx.quadraticCurveTo(points[i].x, points[i].y, points[i+1].x,points[i+1].y);