C++ AbstractVehicle::speed方法代码示例

float3
OpenSteer::SteerLibrary::
steerForTargetSpeed (const AbstractVehicle& v, 
					 const float targetSpeed)
{
    const float mf = v.maxForce ();
    const float speedError = targetSpeed - v.speed ();
    return float3_scalar_multiply(make_float3(v.forward ()), clip (speedError, -mf, +mf));
}

float
OpenSteer::SteerLibrary::
computeNearestApproachPositions (const AbstractVehicle& v, 
								 AbstractVehicle& other, 
								 float time)
{
	const float3 myTravel = float3_scalar_multiply(make_float3(v.forward()), v.speed () * time);
	const float3 otherTravel = float3_scalar_multiply(make_float3(other.forward()), other.speed () * time);

    const float3 myFinal = float3_add(make_float3(v.position()), myTravel);
    const float3 otherFinal = float3_add(make_float3(other.position()), otherTravel);

    // xxx for annotation
    ourPositionAtNearestApproach = myFinal;
    hisPositionAtNearestApproach = otherFinal;

	return float3_distance(myFinal, otherFinal);
}

float3
OpenSteer::SteerLibrary::
steerToFollowPath (const AbstractVehicle& v, 
				   const int direction,
                   const float predictionTime,
                   Pathway& path)
{
    // our goal will be offset from our path distance by this amount
    const float pathDistanceOffset = direction * predictionTime * v.speed();

    // predict our future position
    const float3 futurePosition = v.predictFuturePosition (predictionTime);

    // measure distance along path of our current and predicted positions
    const float nowPathDistance =
        path.mapPointToPathDistance (make_float3(v.position ()));
    const float futurePathDistance =
        path.mapPointToPathDistance (futurePosition);

    // are we facing in the correction direction?
    const bool rightway = ((pathDistanceOffset > 0) ?
                           (nowPathDistance < futurePathDistance) :
                           (nowPathDistance > futurePathDistance));

    // find the point on the path nearest the predicted future position
    // XXX need to improve calling sequence, maybe change to return a
    // XXX special path-defined object which includes two float3s and a 
    // XXX bool (onPath,tangent (ignored), withinPath)
    float3 tangent;
    float outside;
    const float3 onPath = path.mapPointToPath (futurePosition,
                                             // output arguments:
                                             tangent,
                                             outside);

    // no steering is required if (a) our future position is inside
    // the path tube and (b) we are facing in the correct direction
    if ((outside < 0) && rightway)
    {
        // all is well, return zero steering
        return float3_zero();
    }
    else
    {
        // otherwise we need to steer towards a target point obtained
        // by adding pathDistanceOffset to our current path position

        float targetPathDistance = nowPathDistance + pathDistanceOffset;
        float3 target = path.mapPathDistanceToPoint (targetPathDistance);

        annotatePathFollowing (futurePosition, onPath, target, outside);

        // return steering to seek target on path
        return steerForSeek (v, target);
    }
}

float3
OpenSteer::SteerLibrary::
steerToAvoidObstacle (const AbstractVehicle& v, 
					  const float minTimeToCollision,
                      const Obstacle& obstacle)
{
    const float3 avoidance = obstacle.steerToAvoid (v, minTimeToCollision);

    // XXX more annotation modularity problems (assumes spherical obstacle)
    if (!float3_equals(avoidance, float3_zero()))
        annotateAvoidObstacle (minTimeToCollision * v.speed());

    return avoidance;
}

float3
OpenSteer::SteerLibrary::
steerForEvasion (const AbstractVehicle& v, 
				 const AbstractVehicle& menace,
                 const float maxPredictionTime)
{
    // offset from this to menace, that distance, unit vector toward menace
    const float3 offset = float3_subtract(make_float3(menace.position()), make_float3(v.position()));
    const float distance = float3_length(offset);

    const float roughTime = distance / menace.speed();
    const float predictionTime = ((roughTime > maxPredictionTime) ?
                                  maxPredictionTime :
                                  roughTime);

    const float3 target = menace.predictFuturePosition (predictionTime);

    return steerForFlee (v, target);
}

OpenSteer::Vec3 
OpenSteer::Obstacle::PathIntersection::
steerToAvoidIfNeeded (const AbstractVehicle& vehicle,
                      const float minTimeToCollision) const
{
    // if nearby intersection found, steer away from it, otherwise no steering
    const float minDistanceToCollision = minTimeToCollision * vehicle.speed();
    if (intersect && (distance < minDistanceToCollision))
    {
        // compute avoidance steering force: take the component of
        // steerHint which is lateral (perpendicular to vehicle's
        // forward direction), set its length to vehicle's maxForce
        Vec3 lateral = steerHint.perpendicularComponent (vehicle.forward ());
        if (lateral == Vec3::zero)
            lateral = vehicle.side ();
        return lateral.normalize () * vehicle.maxForce ();
    }
    else
    {
        return Vec3::zero;
    }
}

float3
OpenSteer::SteerLibrary::
steerToAvoidNeighbors (const AbstractVehicle& v, 
					   const float minTimeToCollision,
                       const AVGroup& others)
{
    // first priority is to prevent immediate interpenetration
    const float3 separation = steerToAvoidCloseNeighbors (v, 0, others);
    
	if (!float3_equals(separation, float3_zero()))
		return separation;

    // otherwise, go on to consider potential future collisions
    float steer = 0;
    AbstractVehicle* threat = NULL;

    // Time (in seconds) until the most immediate collision threat found
    // so far.  Initial value is a threshold: don't look more than this
    // many frames into the future.
    float minTime = minTimeToCollision;

    // xxx solely for annotation
    float3 xxxThreatPositionAtNearestApproach;
    float3 xxxOurPositionAtNearestApproach;

    // for each of the other vehicles, determine which (if any)
    // pose the most immediate threat of collision.
    for (AVIterator i = others.begin(); i != others.end(); i++)
    {
        AbstractVehicle& other = **i;
        if (&other != &v)
        {	
            // avoid when future positions are this close (or less)
            const float collisionDangerThreshold = v.radius() * 2;

            // predicted time until nearest approach of "this" and "other"
            const float time = predictNearestApproachTime (v, other);

            // If the time is in the future, sooner than any other
            // threatened collision...
            if ((time >= 0) && (time < minTime))
            {
                // if the two will be close enough to collide,
                // make a note of it
                if (computeNearestApproachPositions (v, other, time)
                    < collisionDangerThreshold)
                {
                    minTime = time;
                    threat = &other;
                    xxxThreatPositionAtNearestApproach
                        = hisPositionAtNearestApproach;
                    xxxOurPositionAtNearestApproach
                        = ourPositionAtNearestApproach;
                }
            }
        }
    }

    // if a potential collision was found, compute steering to avoid
    if (threat != NULL)
    {
        // parallel: +1, perpendicular: 0, anti-parallel: -1
        float parallelness = float3_dot(make_float3(v.forward()), make_float3(threat->forward()));
        float angle = 0.707f;

        if (parallelness < -angle)
        {
            // anti-parallel "head on" paths:
            // steer away from future threat position
            float3 offset = float3_subtract(xxxThreatPositionAtNearestApproach, make_float3(v.position()));
            float sideDot = float3_dot(offset, v.side());
            steer = (sideDot > 0) ? -1.0f : 1.0f;
        }
        else
        {
            if (parallelness > angle)
            {
                // parallel paths: steer away from threat
                float3 offset = float3_subtract(make_float3(threat->position()), make_float3(v.position()));
                float sideDot = float3_dot(offset, v.side());
                steer = (sideDot > 0) ? -1.0f : 1.0f;
            }
            else
            {
                // perpendicular paths: steer behind threat
                // (only the slower of the two does this)
                if (threat->speed() <= v.speed())
                {
                    float sideDot = float3_dot(v.side(), threat->velocity());
                    steer = (sideDot > 0) ? -1.0f : 1.0f;
                }
            }
        }

        annotateAvoidNeighbor (*threat,
                               steer,
                               xxxOurPositionAtNearestApproach,
                               xxxThreatPositionAtNearestApproach);
    }

//.........这里部分代码省略.........