Sci-Fi Expansion Pack

Energy shield

18,000 points around every walker. Something always gets through, energy weapons hit it hardest, and it collapses for 10 seconds when it runs dry.

Filter, not a hit zone

The shield is not a collider. It sits inside the walker's damage model, after armour, and counts in the same points as the zones. That makes balancing simple: an RPG hit is ~1,300 points whether it lands on the shield or the leg.

//! [Server] Returns the damage that still reaches the walker.
float MyShield_Absorb(float damage, BaseDamageContext ctx)
{
	if (damage <= 0 || m_fShieldPoints <= 0)
		return damage;

	m_fLastHit = Now();				// regeneration waits 5 s after the last hit

	float hold = HOLD_KINETIC;
	float cost = 1.0;
	if (s_bEnergyHit)				// set by the laser around its damage call
	{
		hold = HOLD_ENERGY;
		cost = COST_ENERGY;
	}
	else if (IsExplosive(ctx.damageType))
		hold = HOLD_EXPLOSIVE;

	if (IsPlacedChargeInside(ctx))			// mines / C4 under the walker: no protection
		return damage;

	float absorbed = Math.Min(damage * hold, m_fShieldPoints / cost);
	m_fShieldPoints -= absorbed * cost;
	if (m_fShieldPoints <= 0.5)
	{
		m_fShieldPoints = 0;
		m_fDownUntil = Now() + 10;		// collapsed
	}

	SyncShield();					// replicated percent + hit counter (for the flash)
	return damage - absorbed;
}

Inside the bubble

A rocket explodes at the walker – inside the bubble – but it flew in from outside. A mine was already inside. The difference is the damage source: anything without a projectile move component that sits inside the bubble ellipsoid gets no protection.

bool IsPlacedChargeInside(BaseDamageContext ctx)
{
	IEntity src = ctx.damageSource;
	if (!src || src.FindComponent(ProjectileMoveComponent))
		return false;				// projectile / rocket / grenade: came from outside

	vector o = GetOwner().CoordToLocal(src.GetOrigin()) - BUBBLE_CENTRE;
	vector r = BUBBLE_RADII;			// ellipsoid half axes
	float e = (o[0] / r[0]) * (o[0] / r[0]) + (o[1] / r[1]) * (o[1] / r[1]) + (o[2] / r[2]) * (o[2] / r[2]);
	return e < 1.0;
}

Beams stop at the bubble

Hitscan beams (the laser) do not create a damage context with a projectile – they trace and apply damage themselves. To make them stop at an enemy shield, the beam is intersected with every standing bubble first: ray against ellipsoid, solved in the walker's local frame scaled to a unit sphere.

//! Distance along the ray to the bubble, or -1.
float RayVsBubble(IEntity walker, vector start, vector dir, float range)
{
	vector o = walker.CoordToLocal(start) - BUBBLE_CENTRE;
	vector d = walker.VectorToLocal(dir);
	vector r = BUBBLE_RADII;
	vector os = Vector(o[0] / r[0], o[1] / r[1], o[2] / r[2]);
	vector ds = Vector(d[0] / r[0], d[1] / r[1], d[2] / r[2]);

	float a = vector.Dot(ds, ds);
	float b = 2.0 * vector.Dot(os, ds);
	float c = vector.Dot(os, os) - 1.0;
	if (c < 0)
		return -1;				// starts inside (own walker): no interception

	float disc = b * b - 4.0 * a * c;
	if (disc < 0)
		return -1;
	float t = (-b - Math.Sqrt(disc)) / (2.0 * a);
	if (t < 0 || t > range)
		return -1;
	return t;
}

The bubble effect

The visible bubble (hexagon grid + haze) is a local child entity spawned on every machine with a display – never replicated. It shows while the shield stands and flashes in the direction of each hit, driven by a replicated hit counter and direction. The dedicated server spawns nothing.