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/* Starshatter: The Open Source Project
Copyright (c) 2021-2022, Starshatter: The Open Source Project Contributors
Copyright (c) 2011-2012, Starshatter OpenSource Distribution Contributors
Copyright (c) 1997-2006, Destroyer Studios LLC.
AUTHOR: John DiCamillo
OVERVIEW
========
Seeker Missile (low-level) Artificial Intelligence class
*/
#include "SeekerAI.h"
#include "Ship.h"
#include "Shot.h"
#include "System.h"
#include "WeaponDesign.h"
#include "Clock.h"
// +----------------------------------------------------------------------+
SeekerAI::SeekerAI(SimObject* s)
: SteerAI(s), shot((Shot*) s), orig_target(0),
pursuit(1), delay(0), overshot(false)
{
ai_type = SEEKER;
seek_gain = 25;
seek_damp = 0.55;
}
// +--------------------------------------------------------------------+
SeekerAI::~SeekerAI()
{
if (shot) {
if (shot->Owner())
((Ship*) shot->Owner())->SetMissileEta(shot->Identity(), 0);
}
}
// +--------------------------------------------------------------------+
void
SeekerAI::ExecFrame(double seconds)
{
// setup:
FindObjective();
// adaptive behavior:
Navigator();
}
// +--------------------------------------------------------------------+
void
SeekerAI::Navigator()
{
if (delay > 0) {
delay -= Clock::GetInstance()->Delta();
}
else {
Steer s = SeekTarget();
self->ApplyYaw((float) s.yaw);
self->ApplyPitch((float) s.pitch);
}
}
void
SeekerAI::SetTarget(SimObject* targ, System* sub)
{
if (!orig_target && targ && targ->Type() == SimObject::SIM_SHIP) {
orig_target = (Ship*) targ;
Observe(orig_target);
}
SteerAI::SetTarget(targ, sub);
if (!target) {
shot->SetEta(0);
if (shot->Owner())
((Ship*) shot->Owner())->SetMissileEta(shot->Identity(), 0);
}
}
void
SeekerAI::FindObjective()
{
if (!shot || !target) return;
if (target->Life() == 0) {
if (target != orig_target)
SetTarget(orig_target,0);
else
SetTarget(0,0);
return;
}
Point tloc = target->Location();
tloc = Transform(tloc);
// seeker head limit of 45 degrees:
if (tloc.z < 0 || tloc.z < fabs(tloc.x) || tloc.z < fabs(tloc.y)) {
overshot = true;
SetTarget(0,0);
return;
}
// distance from self to target:
distance = Point(target->Location() - self->Location()).length();
// are we being spoofed?
CheckDecoys(distance);
Point cv = ClosingVelocity();
// time to reach target:
double time = distance / cv.length();
double predict = time;
if (predict > 15)
predict = 15;
// pure pursuit:
if (pursuit == 1 || time < 0.1) {
obj_w = target->Location();
}
// lead pursuit:
else {
// where the target will be when we reach it:
Point run_vec = target->Velocity();
obj_w = target->Location() + (run_vec * predict);
}
// subsystem offset:
if (subtarget) {
Point offset = target->Location() - subtarget->MountLocation();
obj_w -= offset;
}
else if (target->Type() == SimObject::SIM_SHIP) {
Ship* tgt_ship = (Ship*) target;
if (tgt_ship->IsGroundUnit())
obj_w += Point(0,150,0);
}
distance = Point(obj_w - self->Location()).length();
time = distance / cv.length();
// where we will be when the target gets there:
if (predict > 0.1 && predict < 15) {
Point self_dest = self->Location() + cv * predict;
Point err = obj_w - self_dest;
obj_w += err;
}
// transform into camera coords:
objective = Transform(obj_w);
objective.Normalize();
shot->SetEta((int) time);
if (shot->Owner())
((Ship*) shot->Owner())->SetMissileEta(shot->Identity(), (int) time);
}
// +--------------------------------------------------------------------+
void
SeekerAI::CheckDecoys(double target_distance)
{
// if the assigned target has the burner lit,
// ignore the decoys:
if (orig_target && orig_target->Augmenter()) {
SetTarget(orig_target);
return;
}
if (target &&
target == orig_target &&
orig_target->GetActiveDecoys().size()) {
ListIter<Shot> decoy = orig_target->GetActiveDecoys();
while (++decoy) {
double decoy_distance = Point(decoy->Location() - self->Location()).length();
if (decoy_distance < target_distance) {
if (rand() < 1600) {
SetTarget(decoy.value(), 0);
return;
}
}
}
}
}
// +--------------------------------------------------------------------+
bool
SeekerAI::Overshot()
{
return overshot;
}
// +--------------------------------------------------------------------+
Steer
SeekerAI::AvoidCollision()
{
return Steer();
}
// +--------------------------------------------------------------------+
Steer
SeekerAI::SeekTarget()
{
if (!self || !target || Overshot())
return Steer();
return Seek(objective);
}
// +--------------------------------------------------------------------+
bool
SeekerAI::Update(SimObject* obj)
{
if (obj == target) {
if (obj->Type() == SimObject::SIM_SHOT && orig_target != 0)
target = orig_target;
}
if (obj == orig_target)
orig_target = 0;
return SteerAI::Update(obj);
}
const char*
SeekerAI::GetObserverName() const
{
static char name[64];
sprintf_s(name, "SeekerAI(%s)", self->Name());
return name;
}
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