It's been a while since I did any maths* of this kind, so perhaps someone can answer this for me. I don't think this question is exactly what I want, because I am trying to find intersections for precise x values.
So I have a spline which goes from X,Y to XX,YY, with control points at each end. I think I would be correct in saying it will be a quadratic curve (the curve will not cross itself). I plan on using the path routines from the given graphics library (currently thinking HTML5 canvas) to draw this line, so I will not be drawing it myself.
I have a number of points, expressed as X + n, for which I want to find the Y value of the intersection. I am not asking for a position at a given point along the path, I am asking the position on the path where it intersects a line X.
I am planning to draw a vertical line to meet up with it, so if possible it would be great if the point were precise enough to meet up with the curve in a convincing looking way (not off by a couple of pixels).
The routines don't look to hard to draw the line myself, so I could do that and just test (with tolerance) for X values along the plot, if it comes to it.
*Math
