/*
* Returns the crossing point is the line crosses the other line, null if the lines do not cross
* (!) lines are assued to be finite, starting at the start point, and ending at the end point
* @param line the other line
* @param epsilon the amount of error that is permittable for two points to be considered equal
* (two points that are closer than epsilon will be considered equal)
*/
public Point crosses(Line line, double epsilon)
{
if (CoordinateCalculator.hasDifferenceLessThan(end_pt.X, start_pt.X, epsilon) &&
!CoordinateCalculator.hasDifferenceLessThan(line.end_pt.X, line.start_pt.X, epsilon))
{
float crosing_x = end_pt.X;
float crossing_y = line.getSlope() * crosing_x + line.getConstant();
Point crossing_pt = new Point(crosing_x, crossing_y);
if (this.containsInVector(crossing_pt, epsilon) && line.containsInVector(crossing_pt, epsilon))
{
return(crossing_pt);
}
}
else if (!CoordinateCalculator.hasDifferenceLessThan(end_pt.X, start_pt.X, epsilon) &&
CoordinateCalculator.hasDifferenceLessThan(line.end_pt.X, line.start_pt.X, epsilon))
{
float crosing_x = line.end_pt.X;
float crossing_y = getSlope() * crosing_x + getConstant();
Point crossing_pt = new Point(crosing_x, crossing_y);
if (this.containsInVector(crossing_pt, epsilon) && line.containsInVector(crossing_pt, epsilon))
{
return(crossing_pt);
}
}
else if ((CoordinateCalculator.hasDifferenceLessThan(end_pt.X, start_pt.X, epsilon) &&
CoordinateCalculator.hasDifferenceLessThan(line.end_pt.X, line.start_pt.X, epsilon)) ||
(this.getSlope() == line.getSlope()))
{
if (start_pt.isCloseTo(line.getStartPoint(), epsilon) ||
start_pt.isCloseTo(line.getEndPoint(), epsilon))
{
return(start_pt);
}
else if (end_pt.isCloseTo(line.getEndPoint(), epsilon) ||
end_pt.isCloseTo(line.getStartPoint(), epsilon))
{
return(end_pt);
}
}
else
{
float crosing_x = (line.getConstant() - this.getConstant()) / (this.getSlope() - line.getSlope());
float crossing_y = this.getSlope() * crosing_x + this.getConstant();
Point crossing_pt = new Point(crosing_x, crossing_y);
if (this.containsInVector(crossing_pt, epsilon) && line.containsInVector(crossing_pt, epsilon))
{
return(crossing_pt);
}
}
return(null);
}
public void testGetSlope()
{
Line test = new Line(new Point(10, 10), new Point(15, 20));
Assert.AreEqual(2, test.getSlope(), "the slope is correct");
}