/// <seealso cref="Silver.Weight.Raw.Collide.Collider.Collide(Silver.Weight.Raw.Contact[], Silver.Weight.Raw.Body, Silver.Weight.Raw.Body)">
/// </seealso>
public override int Collide(Contact[] contacts, Body bodyA, Body bodyB)
{
Line line = (Line) bodyA.Shape;
Polygon poly = (Polygon) bodyB.Shape;
// TODO: this can be optimized using matrix multiplications and moving only one shape
// specifically the line, because it has only two vertices
Vector2f[] vertsA = line.getVertices(bodyA.GetPosition(), bodyA.Rotation);
Vector2f[] vertsB = poly.GetVertices(bodyB.GetPosition(), bodyB.Rotation);
Vector2f pos = poly.GetCentroid(bodyB.GetPosition(), bodyB.Rotation);
// using the z axis of a 3d Cross product we determine on what side B is
bool isLeftOf = 0 > (pos.x - vertsA[0].x) * (vertsA[1].y - vertsA[0].y) - (vertsA[1].x - vertsA[0].x) * (pos.y - vertsA[0].y);
// to get the proper intersection pairs we make sure
// the line's normal is pointing towards the polygon
// TODO: verify that it's not actually pointing in the opposite direction
if (isLeftOf)
{
Vector2f tmp = vertsA[0];
vertsA[0] = vertsA[1];
vertsA[1] = tmp;
}
// we use the line's normal for our sweepline projection
Vector2f normal = new Vector2f(vertsA[1]);
normal.Sub(vertsA[0]);
normal.Reconfigure(normal.y, - normal.x);
EdgeSweep sweep = new EdgeSweep(normal);
sweep.Insert(0, true, vertsA[0].Dot(normal));
sweep.Insert(0, true, vertsA[1].Dot(normal));
sweep.AddVerticesToSweep(false, vertsB);
int[][] collEdgeCands = sweep.OverlappingEdges;
IntersectionGatherer intGath = new IntersectionGatherer(vertsA, vertsB);
for (int i = 0; i < collEdgeCands.Length; i++)
intGath.Intersect(collEdgeCands[i][0], collEdgeCands[i][1]);
Intersection[] intersections = intGath.Intersections;
return PopulateContacts(contacts, vertsA, vertsB, intersections);
}
/// <summary> Get the edges from a list of vertices that can Collide with the given circle.
/// This uses a sweepline algorithm which is only efficient if some assumptions
/// are indeed true. See CPolygonCPolygonCollider for more information.
///
/// </summary>
/// <param name="vertsA">The vertices of a polygon that is Collided with a circle
/// </param>
/// <param name="centroid">The center of the polygon
/// </param>
/// <param name="radius">The radius of the circle
/// </param>
/// <param name="circlePos">The position (center) of the circle
/// </param>
/// <returns> The list of edges that can Collide with the circle
/// </returns>
protected internal virtual int[][] GetCollisionCandidates(Vector2f[] vertsA, ROVector2f centroid, float radius, ROVector2f circlePos)
{
Vector2f sweepDir = new Vector2f(centroid);
sweepDir.Sub(circlePos);
sweepDir.Normalise(); //TODO: this normalization might not be necessary
EdgeSweep sweep = new EdgeSweep(sweepDir); //vertsA[0], true, true, dist);
sweep.AddVerticesToSweep(true, vertsA);
float circProj = circlePos.Dot(sweepDir);
sweep.Insert(0, false, - radius + circProj);
sweep.Insert(0, false, radius + circProj);
return sweep.OverlappingEdges;
}