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/* _____ _ __ ________ ___ *\
** / ___/(_) |/ / ___/ |__ \ Simple Mechanics Simulator 2 **
** \__ \/ / /|_/ /\__ \ __/ / copyright (c) 2011 Jakob Odersky **
** ___/ / / / / /___/ / / __/ **
** /____/_/_/ /_//____/ /____/ **
\* */
package sims.collision
import sims.math._
/** Common properties of all convex polygons.
* '''Note: convex polygons are not verified to be convex. It is up to the client to ensure this.''' */
trait ConvexPolygon extends Polygon {
/**Returns the projection of this polygon onto the line given by the directional vector <code>axis</code>.
* @param axis directional vector of the line
* @return projection of this polygon*/
override def project(axis: Vector2D) = {
val dir = axis.unit
var min = vertices(0) dot dir
var max = vertices(0) dot dir
for (v <- vertices) {
val d = v dot dir
if (d < min) min = d
if (d > max) max = d
}
new Projection(axis, min, max)
}
/**Checks if the point <code>point</code> is contained in this polygon.
* <p>
* A ray is created, originating from the point and following an arbitrary direction (X-Axis was chosen).
* The number of intersections between the ray and this polygon's sides (including vertices) is counted.
* The amount of intersections with vertices is subtracted form the previous number.
* If the latter number is odd, the point is contained in the polygon.*/
override def contains(point: Vector2D) = {
val r = new Ray(point, Vector2D.i)
var intersections = 0
for (s <- sides; if !(r intersection s).isEmpty) intersections += 1
for (v <- vertices; if (r contains v)) intersections -= 1
intersections % 2 != 0
}
override def support(direction: Vector2D) = {
var maxDistance = vertices(0) dot direction
var maxPoint = vertices(0)
for (v <- vertices) {
val s = v dot direction
if (s > maxDistance) {
maxDistance = s
maxPoint = v
}
}
maxPoint
}
}
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