[Discussion]: Guided projectiles

[sumghai]

Although most ranged combat in CE occurs at pawn-to-pawn ranges with weapons that fire projectiles on a purely ballistic trajectory, guided projectiles could add a new element to gameplay:

• Some existing rockets/missiles in the CE ammo library (e.g. Javelin, MBT-LAW, APKWS, Tomahawk TLAM) could benefit from having a guidance system that they already possess in real life
• Guided munitions launched by vehicle-like pawns (e.g. Hellfire missiles from SRTS gunships/helicopters)
• Guided mortar/artillery rounds (e.g. M982 Excalibur) for improved accuracy against sieges
• Throwable homing grenades, a la COD:AW's Smart Grenades (@Tostov)
• Inter-map artillery strikes, where a spotter pawn on a enemy map improves the accuracy of rounds launched from the home colony map

Types of Guidance

Type	Description	Target Type	Relative Crafting Cost	Player Countermeasures
Manual/Command	The firing pawn/turret continues to 'aim' the weapon at the target as it guides the projectile, without stopping to reload or switch targets	All	Low (+1 Industrial Component)	Seeking cover and breaking line-of-sight
Fire-and-forget (Infrared)	The projectile automatically seeks out the target's body heat emissions, freeing the firing pawn/turret to reload or switch targets	Organic humanoid/animal pawns, vehicles with running engines	Medium (+2 Industrial Components	Decoy heat sources (e.g. fires, heaters, flares)
Fire-and-forget (Radar)	The projectile automatically seeks out the target's electronic emissions, freeing the firing pawn/turret to reload or switch targets	Mechanoids	High (+1~2 Advanced Components)	Very difficult to jam, unless the player builds jammers/dazzlers

Implementation

Ideally via a custom comp, so that it can be easily added to new/existing projectiles as required:

<li Class="CombatExtended.CompProperties_GuidedProjectile">
        <maxAngleChangeRate />
        <maxLifetime />
        <detonateAtMaxLifetime />
        <seekerMode />
</li>

Parameter	Description	Allowed Values	Default (if unspecified)
maxAngleChangeRate	Max angular change per tick/second of projectile	Integer: 0~90	?
maxLifetime	Max number of seconds projectile has to seek its target before its guidance behaviour stops	Integer: 0-?	10
detonateAtMaxLifetime	Whether it detonates at the end of its max lifetime	Boolean: true (explodes) false (reverts to unguided projectile)	false
seekerMode	How the seeker operates	Enum: manual,infrared,radar	manual

Alternative approaches to tuning:

• PID tuning (more accurate, but difficult for the layperson to set up for each new projectile)
• Account for round aerodynamics? (e.g. round diameter, length -> affects rate of turn)

Additional thoughts

• Pawns and vehicles could generate body heat proportional to body size
• Mechanoids could potentially run on "cold" power sources, but have radio/wireless emissions from communicating with each other
• Pawn/turret aiming/firing/reloading behaviour will need to be modified to support manual guidance mode that suspends reloading or target switching while the current projectile is in flight.

[fors4ken]

I like this idea a lot.

Should there be a distinction between radar and IR guidance?

Not sure about this. I just hope it doesn't end up as a bloated feature that no one likes/uses.

[Tostov]

It should be possible to set a guided munition as either fire and forget or as manually guided (and the systems for supporting that, such as making a pawn/turret continue to 'aim' the weapon without stopping to reload/switching targets).

Given that dodging isn't really going to be a thing, I think just a simple max angular change per tick/second parameter is probably entirely sufficent. Making it easy to set up is probably the most ideal way to do it here.

[sumghai]

Should there be a distinction between radar and IR guidance?

Not sure about this. I just hope it doesn't end up as a bloated feature that no one likes/uses. I brought up the subject of different guidance types so that it is possible to counter against them, discouraging players from simply bum-rushing research towards an "I win" button.

Perhaps there could be research/crafting cost differences?:

• IR guided rounds are easier to make but more easily spoofed by decoy heat sources
• Radar/anti-radiation guided rounds cost more and require unlocking later research nodes, but are less susceptible to spoofing (unless players invest heavily in jamming towers or such like)

It should be possible to set a guided munition as either fire and forget or as manually guided (and the systems for supporting that, such as making a pawn/turret continue to 'aim' the weapon without stopping to reload/switching targets).

Oooh, I quite like this idea.

In a similar vein to my preceding comment, perhaps command/manually-guided systems are cheaper to build and unlocked earlier in the research tree, compared with fire-and-forget?

[sumghai]

Updated OP with feedback from @fors4ken and @Tostov.

@CombatExtended-Continued/coders @CombatExtended-Continued/playtesters - feel free to share your thoughts as well.

[perkinslr]

From a coding perspective, letting the projectile change x MoA / tick is the simplest approach, as is tying it to a marker like the Mortars currently use. Trying to decide "what's the warmest thing in X area" would be considerably less clear. In addition to the max lifetime, there should be a setting for what the projectile does at the end of the lifetime (detonates or just turns into a dumb projectile).

[sumghai]

Trying to decide "what's the warmest thing in X area" would be considerably less clear.

And potentially computationally expensive, if calculated across the whole map at regular intervals.

there should be a setting for what the projectile does at the end of the lifetime (detonates or just turns into a dumb projectile).

Perhaps as a simple boolean parameter?

detonateAtMaxLifetime: true by default, false for turning into a dumb projectile

[perkinslr]

Not likely to be that computationally expensive. You can cache the items of interest, so it's pretty close to O(1) with regard to the number of projectiles. But that does mean that the program complexity is higher, which increases the probability of errors.

And yes, a simple boolean is likely sufficient, if anyone can think of another behavior beyond "explode or become dumb" then it could become an enum, but I can't think of anything else. I suppose "land" could be a possibility for some munitions...

[sumghai]

Not likely to be that computationally expensive. You can cache the items of interest, so it's pretty close to O(1) with regard to the number of projectiles. But that does mean that the program complexity is higher, which increases the probability of errors.

Ah, I see.

And yes, a simple boolean is likely sufficient, if anyone can think of another behavior beyond "explode or become dumb" then it could become an enum, but I can't think of anything else. I suppose "land" could be a possibility for some munitions...

Yeah, a boolean would be sufficient. I'll update the OP in a sec.

For the purposes of RimWorld and CE, we can assume there are no dud rounds. And any suicide drone/missiles would probably be implemented as pawns instead.

[Arcalane]

Another potential element/reference for your first list could be Cyberpunk 2077's Smart weapons. Whilst they're not as powerful per-hit as regular firearms, they're significantly more accurate if used correctly. There's an added catch in that they require supporting hardware too.

Something as simple as 'requires a gunlink eyepiece, qualifying helmet (i.e. power armour), or any tier of bionic eye' could be a useful balancing factor for high-end stuff, if it's possible to check for that kind of thing without too much slowdown.

And yes, a simple boolean is likely sufficient, if anyone can think of another behavior beyond "explode or become dumb" then it could become an enum, but I can't think of anything else. I suppose "land" could be a possibility for some munitions...

Depending on the strength (or relative value/difficulty of creating) of the warhead you might not want it to automatically detonate or continue on to potentially detonate when it misses, especially if there's a risk of starting giant forest fires or something. Having projectiles that can land intact on a miss (% chance?) seems more like a thing for bows and similar low-tech weapons though.

ed: actually, 'create armed object' could also be useful as a general projectile behaviour, then you could add things like advanced grenades for grenade launchers. especially if you could do something like a grenade that detonates if it hits a pawn but turns into a timed or proximity grenade if it hits a wall.

If you were feeling adventurous, the ability for a secondary pawn to guide missiles using a handheld designator 'weapon' (similar to how binocs are supposed to improve mortar accuracy?) could be interesting. probably tricky to code though.