Question

So I need to know the Distance from a point to a line (in 2D space), given two coordinates of the line (AB).

Here is what I have so far:

public double pointToLineDistance(Point A, Point B, Point P)
{
    double normalLength = Math.sqrt((B.x - A.x) * (B.x - A.x) + (B.y - A.y) * (B.y - A.y));
    return Math.abs((P.x - A.x) * (B.y - A.y) - (P.y - A.y) * (B.x - A.x)) / normalLength;
}

But I also need to get the coordinates of the point where the perpendicular line intersects with the AB line (it’s ok if it’s outside this segment).

Any ideas?

Answer 1

The idea is to construct an equation of the line going through the points A and B. When you have constructed that equation, you construct an equation of a line that goes through P and is perpendicular to AB. The equation for the perpendicular has coefficients that are easily derived from the equation for the AB-line. Once you have two equations, solving them will give you the coordinate of the intersection.

Is this for homework?