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/* _____ _ __ ________ ___ *\
** / ___/(_) |/ / ___/ |__ \ Simple Mechanics Simulator 2 **
** \__ \/ / /|_/ /\__ \ __/ / copyright (c) 2011 Jakob Odersky **
** ___/ / / / / /___/ / / __/ **
** /____/_/_/ /_//____/ /____/ **
\* */
package sims.collision
import scala.math._
import sims.math._
/**A base trait for all linear geometric elements specified by one point and a direction.
* @throws IllegalArgumentException if the directional vector is the null vector*/
trait Linear {
/**A point contained in this linear element.*/
val point: Vector2D
/**Direction vector.*/
val direction: Vector2D
/**Unit directional vector.*/
lazy val direction0 = direction.unit
/**Right normal vector to <code>direction</code>.*/
lazy val rightNormal = direction.rightNormal
/**Right normal unit vector to <code>direction</code>.*/
lazy val rightNormal0 = rightNormal.unit
/**Left normal vector to <code>direction</code>.*/
lazy val leftNormal = direction.leftNormal
/**Left normal unit vector to <code>direction</code>.*/
lazy val leftNormal0 = leftNormal.unit
///**Computes the closest point on this linear element to a given point.*/
//def closest(point: Vector2D): Vector2D
///**Computes the shortest distance form this linear element to a given point.*/
//def distance(point: Vector2D) = (closest(point) - point).length
require(direction != 0, "A linear element's direction cannot be the null vector.")
}
object Linear {
/** Clips a segment passing through points `p1` and `p2` to a half plain
* given by a point `p` and a normal (pointing into the plain) `normal`. */
def clip(p1: Vector2D, p2: Vector2D, p: Vector2D, normal: Vector2D): List[Vector2D] = {
val normal0 = normal.unit
val direction = p2 - p1
val d1 = (p1-p) dot normal0
val d2 = (p2-p) dot normal0
if (d1 < 0 && d2 < 0) return Nil
if (d1 >= 0 && d2 >= 0) return List(p1, p2)
val intersection = p1 + direction * abs(d1) / (abs(d1) + abs(d2))
val inside = if (d1 > 0) p1 else p2
List(inside, intersection)
}
}
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