Spring Engine

Formally known as TA:Spring which was developed by Swedish Yankspankers (SY) whose initial goal was to have a open source 3D RTS with some elements from Total Annihilation, but now since the Swedish Yankspankers are not developing it anymore, it is maintained by a few other programmers, whose goal is to make Spring Engine a generic RTS engine instead of being specially aimed for Total Annihilation.

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Pros:

• FOSS, a jew free experience.
• Multi-platform, Linux and Windows are supported, Mac support is not always guaranteed.
• No knowledge of programming is needed, all you need is a text editor and a modelling program.
• It is easy to create new assets for it.
• Assimp support: .3ds, .dae, .lwo, .blend, .obj.
• Legacy support: .3do (used by Total Annihilation) and .s3o (Springs own model format).
• Lua scripting support, which allows you to do a lot of things which wouldn't be possible otherwise.
• Maps and Games can have options settings which can be changed in the lobby program such as Spring Lobby or TAS Client.
• Support for AI and making your own AI program.
• Projectiles have actual physic properties and thus doesn't act like a magic bullet i.e a Artillery Shell can collide with the terrain.
• Several weapon types such as: Laser beam or bolt, Cannon, (Homing) Missiles, Torpedos and Vertical Missiles.
• Support for Energy Shields.
• Several weapons can act as interceptor.
• Vehicle types support: Tanks/Car, KBot (Mechs with legs), Hovercraft, U-Boat, Ships, Airplanes, Gunships.
• Terrain is height map based and can be deformed by scripts or projectiles.
• Particles support (Called CEG: Custom Explosion Generator)

Cons:

• Pathfinder is broken, units sometimes get stuck or forming as a clump of blobs. Which hasn't been fixed for several years.
• Community is relative small and thus the player base is small as well.
• No skeleton support, Organic units such as Infantry are stuck using per-object animation.
• No out of the box mission support or campaigns in general.
• Particles cannot have animated sprites.
• No bridges support.

Links

• Official website
• Documentation
• Site for games and maps