gzdoom/wadsrc/static/zscript/shared/fastprojectile.txt

// Fast projectiles --------------------------------------------------------

class FastProjectile : Actor
{
	Default
	{
		Projectile;
		MissileHeight 0;
	}
	
	
	virtual void Effect()
	{
		class<Actor> trail = MissileName;
		if (trail != null)
		{
			double hitz = pos.z - 8;

			if (hitz < floorz)
			{
				hitz = floorz;
			}
			// Do not clip this offset to the floor.
			hitz += MissileHeight;
			
			Actor act = Spawn (trail, (pos.xy, hitz), ALLOW_REPLACE);
			if (act != null)
			{
				if (bGetOwner && target != null)
					act.target = target;
				else
					act.target = self;
				
				act.angle = angle;
				act.pitch = pitch;
			}
		}
	}
	
	//----------------------------------------------------------------------------
	//
	// AFastProjectile :: Tick
	//
	// Thinker for the ultra-fast projectiles used by Heretic and Hexen
	//
	//----------------------------------------------------------------------------

	override void Tick ()
	{
		ClearInterpolation();
		double oldz = pos.Z;

		if (isFrozen())
			return;

		// [RH] Ripping is a little different than it was in Hexen
		FCheckPosition tm;
		tm.DoRipping = bRipper;

		int count = 8;
		if (radius > 0)
		{
			while (abs(Vel.X) >= radius * count || abs(Vel.Y) >= radius * count)
			{
				// we need to take smaller steps.
				count += count;
			}
		}

		if (height > 0)
		{
			while (abs(Vel.Z) >= height * count)
			{
				count += count;
			}
		}

		// Handle movement
		bool ismoved = Vel != (0, 0, 0)
			// Check Z position set during previous tick.
			// It should be strictly equal to the argument of SetZ() function.
			|| (   (pos.Z != floorz           ) /* Did it hit the floor?   */
				&& (pos.Z != ceilingz - Height) /* Did it hit the ceiling? */ );

		if (ismoved)
		{
			// force some lateral movement so that collision detection works as intended.
			if (bMissile && Vel.X == 0 && Vel.Y == 0 && !IsZeroDamage())
			{
				Vel.X = MinVel;
			}

			Vector3 frac = Vel / count;
			int changexy = frac.X != 0 || frac.Y != 0;
			int ripcount = count / 8;
			for (int i = 0; i < count; i++)
			{
				if (changexy)
				{
					if (--ripcount <= 0)
					{
						tm.ClearLastRipped();	// [RH] Do rip damage each step, like Hexen
					}
					
					if (!TryMove (Pos.XY + frac.XY, true, NULL, tm))
					{ // Blocked move
						if (!bSkyExplode)
						{
							let l = tm.ceilingline;
							if (l &&
								l.backsector &&
								l.backsector.GetTexture(sector.ceiling) == skyflatnum)
							{
								let posr = PosRelative(l.backsector);
								if (pos.Z >= l.backsector.ceilingplane.ZatPoint(posr.XY))
								{
									// Hack to prevent missiles exploding against the sky.
									// Does not handle sky floors.
									Destroy ();
									return;
								}
							}
							// [RH] Don't explode on horizon lines.
							if (BlockingLine != NULL && BlockingLine.special == Line_Horizon)
							{
								Destroy ();
								return;
							}
						}

						ExplodeMissile (BlockingLine, BlockingMobj);
						return;
					}
				}
				AddZ(frac.Z);
				UpdateWaterLevel ();
				oldz = pos.Z;
				if (oldz <= floorz)
				{ // Hit the floor

					if (floorpic == skyflatnum && !bSkyExplode)
					{
						// [RH] Just remove the missile without exploding it
						//		if this is a sky floor.
						Destroy ();
						return;
					}

					SetZ(floorz);
					HitFloor ();
                    Destructible.ProjectileHitPlane(self, SECPART_Floor);
					ExplodeMissile (NULL, NULL);
					return;
				}
				if (pos.Z + height > ceilingz)
				{ // Hit the ceiling

					if (ceilingpic == skyflatnum && !bSkyExplode)
					{
						Destroy ();
						return;
					}

					SetZ(ceilingz - Height);
                    Destructible.ProjectileHitPlane(self, SECPART_Ceiling);
					ExplodeMissile (NULL, NULL);
					return;
				}
				CheckPortalTransition();
				if (changexy && ripcount <= 0) 
				{
					ripcount = count >> 3;

					// call the 'Effect' method.
					Effect();
				}
			}
		}
		if (!CheckNoDelay())
			return;		// freed itself
		// Advance the state
		if (tics != -1)
		{
			if (tics > 0) tics--;
			while (!tics)
			{
				if (!SetState (CurState.NextState))
				{ // mobj was removed
					return;
				}
			}
		}
	}
}