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/*
* Simple Mechanics Simulator (SiMS)
* copyright (c) 2009 Jakob Odersky
* made available under the MIT License
*/
package sims.geometry
import sims.math._
import Math._
/**A ray.
* @param point a point on the ray
* @param direction this ray's directional vector
* @throws IllegalArgumentException if the directional vector is the null vector*/
case class Ray(point: Vector2D, direction: Vector2D) {
require(direction != Vector2D.Null, "A ray's direction cannot be given by a null vector!")
/**Checks this ray and the given segment for intersection.
* @param s the segment to test for intersection*/
def intersects(s: Segment) = {
val p1 = point
val p2 = point + direction
val p3 = s.vertex1
val p4 = s.vertex2
val d = (p4.y - p3.y) * (p2.x - p1.x) - (p4.x - p3.x) * (p2.y - p1.y)
val na = (p4.x - p3.x) * (p1.y - p3.y) - (p4.y - p3.y) * (p1.x - p3.x)
val nb = (p2.x - p1.x) * (p1.y - p3.y) - (p2.y - p1.y) * (p1.x - p3.x)
if (d == 0 && na == 0 && nb == 0)
true //lines are coincident
else if (d == 0)
false //parallel
else {
val ua = na / d
val ub = nb / d
(ub >= 0) && (ub <= 1) && (ua >= 0)
}
}
/**Checks if this ray contains the point <code>p</code>.*/
def contains(p: Vector2D) = {
val v = p - point
p == point ||
Matrix22(direction, v).det == 0 &&
signum(direction.x) == signum(v.x) &&
signum(direction.y) == signum(v.y)
}
}
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