// [MC] Was part of P_Thing_Projectile, now its own function for use in ZScript.
// Aims mobj at targ based on speed and targ's velocity.
static void VelIntercept(AActor *targ, AActor *mobj, double speed, bool aimpitch = false, bool oldvel = false, bool leadtarget = true)
{
if (targ == nullptr || mobj == nullptr) return;
DVector3 aim = mobj->Vec3To(targ);
aim.Z += targ->Height / 2;
if (leadtarget && speed > 0 && !targ->Vel.isZero())
{
// Aiming at the target's position some time in the future
// is basically just an application of the law of sines:
// a/sin(A) = b/sin(B)
// Thanks to all those on the notgod phorum for helping me
// with the math. I don't think I would have thought of using
// trig alone had I been left to solve it by myself.
DVector3 tvel = targ->Vel;
if (!(targ->flags & MF_NOGRAVITY) && targ->waterlevel < 3)
{ // If the target is subject to gravity and not underwater,
// assume that it isn't moving vertically. Thanks to gravity,
// even if we did consider the vertical component of the target's
// velocity, we would still miss more often than not.
tvel.Z = 0.0;
if (targ->Vel.X == 0 && targ->Vel.Y == 0)
{
InterceptDefaultAim(mobj, targ, aim, speed);
return;
}
}
double dist = aim.Length();
double targspeed = tvel.Length();
double ydotx = -aim | tvel;
double a = g_acos(clamp(ydotx / targspeed / dist, -1.0, 1.0));
double multiplier = double(pr_leadtarget.Random2())*0.1 / 255 + 1.1;
double sinb = -clamp(targspeed*multiplier * g_sin(a) / speed, -1.0, 1.0);
DVector3 prevel = mobj->Vel;
// Use the cross product of two of the triangle's sides to get a
// rotation vector.
DVector3 rv(tvel ^ aim);
// The vector must be normalized.
rv.MakeUnit();
// Now combine the rotation vector with angle b to get a rotation matrix.
DMatrix3x3 rm(rv, g_cos(g_asin(sinb)), sinb);
// And multiply the original aim vector with the matrix to get a
// new aim vector that leads the target.
DVector3 aimvec = rm * aim;
// And make the projectile follow that vector at the desired speed.
mobj->Vel = aimvec * (speed / dist);
mobj->AngleFromVel();
if (oldvel)
{
mobj->Vel = prevel;
}
if (aimpitch) // [MC] Ripped right out of A_FaceMovementDirection
{
const DVector2 velocity = mobj->Vel.XY();
mobj->Angles.Pitch = -VecToAngle(velocity.Length(), mobj->Vel.Z);
}
}
else
{
InterceptDefaultAim(mobj, targ, aim, speed);
}
}
bool APathFollower::Interpolate ()
{
DVector3 dpos(0, 0, 0);
FLinkContext ctx;
if ((args[2] & 8) && Time > 0.f)
{
dpos = Pos();
}
if (CurrNode->Next==NULL) return false;
UnlinkFromWorld (&ctx);
DVector3 newpos;
if (args[2] & 1)
{ // linear
newpos.X = Lerp(CurrNode->X(), CurrNode->Next->X());
newpos.Y = Lerp(CurrNode->Y(), CurrNode->Next->Y());
newpos.Z = Lerp(CurrNode->Z(), CurrNode->Next->Z());
}
else
{ // spline
if (CurrNode->Next->Next==NULL) return false;
newpos.X = Splerp(PrevNode->X(), CurrNode->X(), CurrNode->Next->X(), CurrNode->Next->Next->X());
newpos.Y = Splerp(PrevNode->Y(), CurrNode->Y(), CurrNode->Next->Y(), CurrNode->Next->Next->Y());
newpos.Z = Splerp(PrevNode->Z(), CurrNode->Z(), CurrNode->Next->Z(), CurrNode->Next->Next->Z());
}
SetXYZ(newpos);
LinkToWorld (&ctx);
if (args[2] & 6)
{
if (args[2] & 8)
{
if (args[2] & 1)
{ // linear
dpos.X = CurrNode->Next->X() - CurrNode->X();
dpos.Y = CurrNode->Next->Y() - CurrNode->Y();
dpos.Z = CurrNode->Next->Z() - CurrNode->Z();
}
else if (Time > 0.f)
{ // spline
dpos = newpos - dpos;
}
else
{
int realarg = args[2];
args[2] &= ~(2|4|8);
Time += 0.1f;
dpos = newpos;
Interpolate ();
Time -= 0.1f;
args[2] = realarg;
dpos = newpos - dpos;
newpos -= dpos;
SetXYZ(newpos);
}
if (args[2] & 2)
{ // adjust yaw
Angles.Yaw = dpos.Angle();
}
if (args[2] & 4)
{ // adjust pitch; use floats for precision
double dist = dpos.XY().Length();
Angles.Pitch = dist != 0.f ? VecToAngle(dist, -dpos.Z) : 0.;
}
}
else
{
if (args[2] & 2)
{ // interpolate angle
DAngle angle1 = CurrNode->Angles.Yaw.Normalized180();
DAngle angle2 = angle1 + deltaangle(angle1, CurrNode->Next->Angles.Yaw);
Angles.Yaw = Lerp(angle1.Degrees, angle2.Degrees);
}
if (args[2] & 1)
{ // linear
if (args[2] & 4)
{ // interpolate pitch
Angles.Pitch = Lerp(CurrNode->Angles.Pitch.Degrees, CurrNode->Next->Angles.Pitch.Degrees);
}
}
else
{ // spline
if (args[2] & 4)
{ // interpolate pitch
Angles.Pitch = Splerp(PrevNode->Angles.Pitch.Degrees, CurrNode->Angles.Pitch.Degrees,
CurrNode->Next->Angles.Pitch.Degrees, CurrNode->Next->Next->Angles.Pitch.Degrees);
}
}
}
}
return true;
}
