Line intersection

> Is there a method in Java that can calculate the

> intersection of two lines. I know that there is a

> Line2D.lineIntersects but this method only returns

> true or false if the two lines intersect. I need the

> X, Y point where the 2 lines intersect.

That point should be very easy to calculate, unless the lines are parallell or close to.

MLRona at 2007-7-13 16:58:43 >

> > > That point should be very easy to calculate,

> > > unless

> > > the lines are parallell or close to.

> >

> > Why would lines being close to parallel make the

> > point of intersection more difficult to calculate?

> A valid point, it makes zero difference (ignoring rounding errors that

> may classify non-parallel lines as parallel).

Rounding errors (if, for example ints were involved) leading to

non-parallel being treated as parallel (or vice versa) would be a

problem.

With or without rounding error, the equations can yield "signed infinities"

that have to be dealt with.

Also there could be a question of precision: if the original line

segments were the result of measurement then how close they

are to parallel could make the difference between whether the

intersection is a reliably calculated value, or a more of a guess.

The OP shouldn't be put off! It's a reasonable question, and MLRon's

link provides a simple solution. But it also seems quite reasonable

to warn that - depending on the context of the original problem -

being parallel or close to parallel could involve problems.

pbrockway2a at 2007-7-13 16:58:43 >