Combat systems are combat simulation systems and add-ons which enable vehicles to cause virtual damage in combat-orientated sims. Due to the diversity of vehicles, weapons and manufacturers there are several competing combat simulation systems operating within Second Life® and are commonly simply referred to as 'combat systems' or 'RP (role play) combat systems'. They cater to a wide array of users in a variety of applications depending on the needs and desires of the organizers and participants.
Linden Lab Combat System (LLCS)
The Linden Lab Combat System (LLCS) is the built-in combat simulation system of Second Life® and requires no additional add-ons to function. The LLCS is active in any parcel that the owner has designated as "unsafe". When a user enters a LLCS-enabled region there will be a heart icon with a percentage indicator on their upper menu bar (meaning that they can be killed in that area). When this percentage drops to zero, they are 'dead', and will be teleported to their 'home' location. Users can then teleport back into the combat simulation from their 'home' location, if they want to return to the combat.
Combatants do not lose anything (money, attachments, inventory) if they happen to die in this manner. However, users are reminded never to set their 'home' to an area that has damage enabled, due to the possibility of becoming stuck in an infinite teleport loop which continuously kills and respawns them. In the LLCS, damage is dealt by collisions with 'LlSetDamage' scripted objects. Residents also take damage when they collide with any object, or with the ground (as in falling), at sufficiently high speed. To instantly kill an agent, that agent must be hit with an object that has its damage percent set to 100%. All damage "heals" gradually over time.
Terra Combat System (TCS)
The Terra Combat System (TCS) is an open-source combat system developed by Terra Aeronautics for their combat aircraft. Prior to the advent of Vehicle & Infantry Combat Environment (VICE) in 2007, TCS was practically the de-facto standard of aircraft combat systems. While most of the industry has moved onto VICE and Modern Combat Environment (MCE), TCS continues to be offered through low-budget aircraft, freebies, and older Second Life aircraft.
Vehicle & Infantry Combat Environment (VICE)
The Vehicle & Infantry Combat Environment (VICE) project began in 2007 to address purported shortcomings of many combat systems in Second Life®; mainly revolving around a felt lack of realism, security, performance, or user-support. Following its introduction, the system quickly surpassed TCS and LLCS in terms of popularity and is now found in most combat-enabled aircraft.
As with LLCS and the later MCE, VICE was a physics-based combat system. Unlike other systems it does not use a sensor system to detect hits but real physical bullets. The system in itself is closed and VICE-enabled vehicles are not vulnerable to other non-VICE weapons to assure fairness for all parties. VICE also features area affect damage weapons (bombs) that feature dynamic damage based on blast proximity.
VICE has a vehicle chart of possible vehicle-classes (for example: Aircraft, tanks, fixed guns, boats etc), each class having different strengths and weaknesses. There are a total of 28 different weapon and unit profiles, which can be applied to a variety of Second Life® vehicles and weapons, allowing for a wide range of applications ranging from World War II tank battles to aerial dogfights. Each unit can carry a limited amount of certain weapon systems and payload. Each VICE unit type and weapon has its set of strengths and weaknesses to help balance gameplay.
In early 2010 the creators of the VICE system - Mifune Tribaut and Creeme Pye - departed from Second Life® and consequently the platform is now officially unsupported. This means that although VICE-compatible aircraft continue to function and be sold, the VICE platform itself will not receive official updates and improvements.
Modern Combat Environment (MCE)
Modern Combat Environment (MCE) was developed by Amok Dynamics as a spiritual successor to VICE in early 2012. MCE is a modular system based around a special Heads-up display (HUD). The HUD automatically detects weapons and vehicles as they are worn and displays health, ammunition and team/faction data (which is selected by wearing the appropriate armband). Unlike VICE, weapons and equipment can only be swapped out at the spawning zone for the user's chosen team.
Like VICE, MCE is a physics-based combat system which utilizes physical projectiles, although a particle-based variant is also in development for combat in regions which do not allow the rezzing of physical objects. Other features of the system include safezones, restoration abilities, different weapon classes and ammunition limits, and multiple weapon loadouts based on bodypoints.
As with VICE, MCE has not been without its share of controversy. To counter concerns that previously released VICE-compatible aircraft would be effectively made obsolete by the implementation of the new system, Amok Dynamics assured concerned customers that their purchased products would be upgraded free-of-charge. Allegations of data-collection have also been strenuously denied by Amok. To facilitate the use of MCE, Amok built Olds Air Force Base and the Undine chain of sims in Spring-Summer of 2010. The region is dedicated to modern combat using the system and serves as the primary hub for all-things MCE.
Omega Combat System (OCS)
Omega Combat System (OCS) was developed and released by the Omega Concern in August of 2007, with the release of their initial line of OCS products and the opening of their Fulda Gap combat region. As with many combat systems a specialized OCS HUD is required for combat; as is a compatible weapon/vehicle. Although the Omega Concern developed Fulda Gap to facilitate OCS combat, it must be noted that OCS is a global system, and can be used anywhere in Second Life.
OCS encourages tactical gameplay by imposing real-world limits on players, such as fatigue, stance and movement-relevant weapon accuracy, and persistent usage-based mastery of various classes of weapons. It is one of the few combat systems in Second Life to limit jumping height and impose velocity based 'fall' damage on vehicles and infantry and ensures that players can not spy on each other using an alt-cam by limiting visibility if the camera is moved too far from an avatar. In addition, every OCS-certified weapon features ammunition that is subject to wind deflection and ballistic drop.
In terms of vehicle combat, all OCS-certified vehicles feature localized component damage/failure as a result of combat, which affects their operation. For example, damage to a tank's left track will make the vehicle turn to the left as it moves, and a helicopter with a broken tail rotor will spin out of control until the pilot cuts the turbine and begins an autorotation.
As a result of being used almost exclusively by the Omega Concern, the combat system has not been as widely adopted as TCS, VICE, or MCE. However, Omega Concern states that development of new OCS-enabled products and the extension and refinement of the OCS protocols themselves continue, and will do so for the foreseeable future.