// this version avoids all of the obstacles in an ObstacleGroup
//
// XXX 9-12-03: note this does NOT use the Obstacle::steerToAvoid protocol
// XXX like the older steerToAvoidObstacle does/did. It needs to be fixed
public Vector3 steerToAvoidObstacles(float minTimeToCollision, ArrayList obstacles)
{
Vector3 avoidance = new Vector3();
PathIntersection nearest, next;
nearest = new PathIntersection();
next = new PathIntersection();
float minDistanceToCollision = minTimeToCollision * speed();
next.intersect = 0; // false;
nearest.intersect = 0; // false;
// test all obstacles for intersection with my forward axis,
// select the one whose point of intersection is nearest
//for (ObstacleIterator o = obstacles.begin(); o != obstacles.end(); o++)
for (int i = 0; i < obstacles.Count; i++)
{
SphericalObstacle o = (SphericalObstacle)obstacles[i];
// xxx this should be a generic call on Obstacle, rather than
// xxx this code which presumes the obstacle is spherical
findNextIntersectionWithSphere(o, next);
if ((nearest.intersect == 0) ||
((next.intersect != 0) &&
(next.distance < nearest.distance)))
{
nearest = next;
}
}
// when a nearest intersection was found
if ((nearest.intersect != 0) &&
(nearest.distance < minDistanceToCollision))
{
// show the corridor that was checked for collisions
annotateAvoidObstacle(minDistanceToCollision);
// compute avoidance steering force: take offset from obstacle to me,
// take the component of that which is lateral (perpendicular to my
// forward direction), set length to maxForce, add a bit of forward
// component (in capture the flag, we never want to slow down)
Vector3 offset = Position - nearest.obstacle.center;
//avoidance = offset.perpendicularComponent (forward());
avoidance = OpenSteerUtility.perpendicularComponent(offset, forward());
avoidance.Normalize();//.normalize ();
avoidance *= maxForce();
avoidance += forward() * maxForce() * 0.75f;
}
return(avoidance);
}
// ----------------------------------------------------------------------------
// xxx experiment cwr 9-6-02
public void findNextIntersectionWithSphere(SphericalObstacle obs, PathIntersection intersection)
{
// xxx"SphericalObstacle& obs" should be "const SphericalObstacle&
// obs" but then it won't let me store a pointer to in inside the
// PathIntersection
// This routine is based on the Paul Bourke's derivation in:
// Intersection of a Line and a Sphere (or circle)
// http://www.swin.edu.au/astronomy/pbourke/geometry/sphereline/
float b, c, d, p, q, s;
Vector3 lc;
// initialize pathIntersection object
intersection.intersect = 0;
intersection.obstacle = obs;
// find "local center" (lc) of sphere in boid's coordinate space
lc = localizePosition(obs.center);
// computer line-sphere intersection parameters
b = -2 * lc.z;
c = square(lc.x) + square(lc.y) + square(lc.z) -
square(obs.radius + radius());
d = (b * b) - (4 * c);
// when the path does not intersect the sphere
if (d < 0)
{
return;
}
// otherwise, the path intersects the sphere in two points with
// parametric coordinates of "p" and "q".
// (If "d" is zero the two points are coincident, the path is tangent)
s = (float)System.Math.Sqrt(d);
p = (-b + s) / 2;
q = (-b - s) / 2;
// both intersections are behind us, so no potential collisions
if ((p < 0) && (q < 0))
{
return;
}
// at least one intersection is in front of us
intersection.intersect = 0;
intersection.distance =
((p > 0) && (q > 0)) ?
// both intersections are in front of us, find nearest one
((p < q) ? p : q) :
// otherwise only one intersections is in front, select it
((p > 0) ? p : q);
return;
}
// ----------------------------------------------------------------------------
// xxx experiment cwr 9-6-02
public void findNextIntersectionWithSphere(SphericalObstacle obs, PathIntersection intersection)
{
// xxx"SphericalObstacle& obs" should be "const SphericalObstacle&
// obs" but then it won't let me store a pointer to in inside the
// PathIntersection
// This routine is based on the Paul Bourke's derivation in:
// Intersection of a Line and a Sphere (or circle)
// http://www.swin.edu.au/astronomy/pbourke/geometry/sphereline/
float b, c, d, p, q, s;
Vector3 lc;
// initialize pathIntersection object
intersection.intersect = 0;
intersection.obstacle = obs;
// find "local center" (lc) of sphere in boid's coordinate space
lc = localizePosition (obs.center);
// computer line-sphere intersection parameters
b = -2 * lc.z;
c = square (lc.x) + square (lc.y) + square (lc.z) -
square (obs.radius + radius());
d = (b * b) - (4 * c);
// when the path does not intersect the sphere
if (d < 0) return;
// otherwise, the path intersects the sphere in two points with
// parametric coordinates of "p" and "q".
// (If "d" is zero the two points are coincident, the path is tangent)
s = (float) System.Math.Sqrt(d);
p = (-b + s) / 2;
q = (-b - s) / 2;
// both intersections are behind us, so no potential collisions
if ((p < 0) && (q < 0)) return;
// at least one intersection is in front of us
intersection.intersect = 0;
intersection.distance =
((p > 0) && (q > 0)) ?
// both intersections are in front of us, find nearest one
((p < q) ? p : q) :
// otherwise only one intersections is in front, select it
((p > 0) ? p : q);
return;
}
