HowTo: Make UGL 40mm smoke grenades less bouncy

[Freghar 73]

(I didn't want to release this as a mod because the change is too tiny, but the journey took some time.)

Smoke grenades fired from the under-barrel grenade launcher are VERY bouncy, initial ground hit 200-300m away can bounce even beyond 1km (measured 1.4km max) under some circumstances. Considering these smoke grenades are often used for targeting, this is kind of bad.

To tune this, the obvious way would be to go to CfgAmmo and find that G_40mm_Smoke inherits directly from SmokeShell, the hand grenade, and that there are "deflecting" and "deflectionSlowDown" parameters, both somewhat undocumented. CfgAmmo reference says on "deflecting"

Declares if ammo is deflecting and thus it's deflection angle.

, commy2 expands on it a bit (thanks!), but it doesn't seem to work and neither does "deflectionSlowDown". The other options to reduce bounciness would be ie. "coefGravity" (doesn't work) or "airFriction" (does work, but the usable range goes down much faster than bounciness).

If you look closely, however, you'll notice that SmokeShell has simulation="shotSmokeX" and so do all the inherited grenades. You'll also note that there's "shotSmoke" used by ie. mortar smoke shells and for that one, deflecting/deflectionSlowDown do work! Upon realizing that, the solution was straightforward:

class CfgAmmo {
    class SmokeShell;
    class G_40mm_Smoke : SmokeShell {
        /* inherited from SmokeShell is shotSmokeX which ignores
         * "deflecting" and "deflectionSlowDown" parameters */
        simulation = "shotSmoke";
        /* multiplier; small bounce, on 400m flat ground shot ~10m bounce */
        deflectionSlowDown = 0.3;
    };
};

Would be interesting to know how launched smoke grenades behave IRL to tune this, but the multiplier finally works.

Hopefully this saves time for somebody trying to do the same.

[x3kj 1247]

does deflectionSlowDown=1.0 bring the projectile to an immediate stop or does it mean it won't affect the speed at all?

I'm asking for Biki purposes, because deflectionSlowDown isn't in it and i've haven't seen it before either.

[Freghar 73]

does deflectionSlowDown=1.0 bring the projectile to an immediate stop or does it mean it won't affect the speed at all?

I'm asking for Biki purposes, because deflectionSlowDown isn't in it and i've haven't seen it before either.

Well, it's a velocity multiplier, so 1.0 would mean zero slowdown (the default is 0.8) due to the multiplier itself, gravity/drag/.. would eventually slow it down anyway.

[x3kj 1247]

Thought as mouch - and of course the name is counterintuitive, as is standard for Arma tokens :D

Added https://community.bistudio.com/wiki/CfgAmmo_Config_Reference#deflectionSlowDown

[ussrlongbow 116]

Would be interesting to know how launched smoke grenades behave IRL to tune this, but the multiplier finally works.

Somewhat like this https://www.youtube.com/watch?v=sKPogx816YE

[commy2 188]

deflectionSlowDown  does nothing in Arma 3. It's legacy from A2 and not compatible with PhysX calculated bouncing of Arma 3. Changing the simulation to shotSmoke means that the grenade no longer bounces at all, but it also means that smoke sounds are not played correctly. The simulation shotSmoke in A3 is only used for sub munition of smoke artillery shells which themselves use shotDeply as simulation type.

[x3kj 1247]

deflectionSlowDown  does nothing in Arma 3. It's legacy from A2 and not compatible with PhysX calculated bouncing of Arma 3. Changing the simulation to shotSmoke means that the grenade no longer bounces at all, but it also means that smoke sounds are not played correctly. The simulation shotSmoke in A3 is only used for sub munition of smoke artillery shells which themselves use shotDeply as simulation type.

"Does nothing" is certainly not true. Maybe for grenades and stuff it doesnt work, but it works for shotShell and shotBullet.

One could try and change/apply rvmats with custom bisurf properties to the geo/ geo phys/ fire geo (bisurf has friction and roughness constants) and see if that changes anything to bouncing objects. I wouldnt count on it however.

[sirklejerk 0]

If your goal is purely to stop the grenade once it hits an object, use the code below. This adds an eventHandler to the projectile which sets its velocity to [0,0,0] once it "explodes" (explodes on hit). Simply populate the array with all the class names for your ammo. This method foregoes modifying any config files and can be applied to any mod, so long as you have the class names. As I have many other effects applied to projectiles, I placed this in my initPlayerLocal.sqf script.

addMissionEventHandler ["ProjectileCreated", {
    params ["_projectile"];
        
    _projectile addEventHandler ["Explode", {
    params ["_projectile", "_pos", "_velocity"];
    
    if (typeOf _projectile in ["rhs_40mm_m713_red","rhs_40mm_m714_white","rhs_40mm_m715_green","rhs_40mm_m716_yellow"]) then {_projectile setVelocity [0,0,0]};
    }];
}];