How it worksEdit
Shields are entities created by units and structures as a sacrificial layer preventing damage to the underlying unit or structure. Shields come in two forms: unit-only (or 'personal') and area-coverage. Each have their respective advantages and disadvantages.
Personal shields act like a 'second skin', giving a single unit a regenerative layer of extra hitpoints. Unlike the larger area-coverage shields, attackers cannot move through a personal shield to attack the unit underneath it.
Area-coverage shields protect any friendly unit inside the field, but any unit, including enemy units, can move right through the shield 'bubble.' Player units are able to shoot through their own shields (either from the inside or the outside), but all other factions will be unable to fire through the shield while it is operational. The ability for enemy units to move inside an area-coverage shield represents a significant vulnerability, since shield generators themselves tend to have relatively low hitpoints. (See below for a discussion of relevant tactics.)
Both types of shields act mostly like normal units when it comes to damage; the shield bubble dissipates after taking damage that exceeds the rated shield hit points. However, shields are unique in that they will regenerate very quickly after dissipating (e.g., T2 stationary shields rebuild and reform at full strength after 15-18 seconds). This rapid-rebuild mechanic is a key factor in understanding the effective use of shields.
Maximizing the effectiveness of your shieldsEdit
For mobile units with personal shields, the rebuild mechanic allows them to take damage in battle until their shield is dissipated, then retreat while their shield is restored. Comparable damage to unshielded units would force them to wait for much slower hitpoint regeneration and/or expensive repairs from an engineer.
This rapid-rebuild effect is even greater for area-coverage shields. Layering multiple area-coverage shield bubbles can have a synergistic effect that makes them much more resilient than if they were deployed separately. When the first shield is dissipated, secondary shields can protect the generator while it rebuilds. Since shields rebuild at a much faster rate than their normal regeneration (e.g., 600hp/second rebuild vs 120hp/second regeneration for the UEF SD_-_Pulse), the necessary DPS to defeat these shields increases dramatically when they're layered together and targeted one-by-one. Fortunately for the attacker, weapons with a large damage radius can potentially strike multiple shield bubbles simultaneously.
Because units can walk right through area coverage shields, it is important that walls be built in front of the shield, or point defense/land units, be placed inside of it...a shield generator's hit points are so low, all it takes is 5-6 tech 1 units to have the opportunity to move safely inside and aim directly at the source of the shield, and the shield is as good as gone. In other words, do not give your opponent the opportunity to move inside the shield. AA defense/units are also recommended because Air Transports can drop units inside the shield and gunships can fly under the bubbles of larger shields, allowing them to bypass the shield and target the generator.
T2 Versus T3 ShieldsEdit
A T3 shield generator has a greater radius and more strength than its respective T2 shield generator, but costs, on average, 5x the mass and 8x the energy, for only twice the strength and twice the radius (Note: Double the radius equals quadruple the area). Therefore, T2 shield generators are better in the long run. However, a T3 shield generator is necessary if you need the area coverage and the protection, but don't have enough room for several T2 shield generators.
Any unit with the engineering suite ability can be ordered to assist the shield generator, thereby regenerating the shield at a speed directly proportional to the number and type of engineers assisting it. This can help to prevent and delay the shield from suffering a total collapse which is critical to the survival of the structures under its protection.
Their shields look like glowing squares that move from the top to the bottom of the shield and vary in brightness(the brightness variance moves in waves from the bottom to the top) and pulse lighter to indicate that their shield strength is low. Their T3 Shield Generator has a larger range but weaker shield, perfect for protecting economy farms.
Their shields look like a rather thick purplish bubble that has lighter colored 2D bubble outlines moving about the shield surface. The shield signifies it being low on energy by pulsing a reddish color. The Cybran faction has the distinction of being the only faction to not have any mobile shield generators, or units with personal shields. They also have the best standard shields but the worst fully-upgraded shields.
Their shields look like a terrain-colored (with a slight green tint) bubble with moving darker points on the shield surface, and the shields glow brighter to signify low health. Their T3 Shield Generator has a higher health but a lower range, perfect for protecting turrets and artillery and such.
Their shields look sort of like horizontal currents of teal smoke moving toward the top of the bubble and fading away as it goes up. Their shields have a combination of high strength and size making them equally useful at protecting fragile structures or large ones. As an offset, they cost slightly more than any of the other faction's shield generators. It is also important to note that unlike the other factions' shield domes, the coloration or pattern of the dome's surface does not change when damaged, making it difficult to determine which shields are close to failure. Seraphim shields also have the longest recharge time of any other factions' shields.