Formats/Particle
Particle effects work differently than in Quake 3 but the same as Tremulous. Please see the Tremulous documentation (pdf) for information on creating particle effects for now.
Particle files must be located in the VFS at scripts/*.particle. A particle file may specify any number of particle systems.
Particle format is game-specific (mods may modify it).
To look for examples of how some particle feature is used, you may use this particle keyword directory.
How it works
A particle renders as either a polygon with the specified texture(s), or a model.
A texture-based particle is rendered as a square polygon oriented opposite to the view direction. The square may be rotated around the view axis, if specified in the particle file. Rotation means the corners of the square aren't aligned with the corners of the window.
There is a correspondence between (texture-based) particles and trails, and the two types of autosprite shaders: particles are to deformVertex autosprite as trails are to deformVertex autosprite2. deformVertex autosprite polygons can be placed in maps. They must be square and are automatically rotated so that, like particles, they are oriented opposite the view axis. Meanwhile trails and autosprite2 polygons rotate to face the viewer (NOT the view direction!), but only around a single axis.
Discouraged features in particle files
realLight should not be used. This causes the particle to be lit using a sample from the lightgrid. This is a bad idea because it results in synchronous queries between the cgame and the renderer. Plus, it does not respond to realtime lights. Use a shader with light mapping enabled instead.
Tools (which do not actually deal with particle systems)
There is a so-called particle effects editor for Quake 3 that will likely need much modification to work with the Tremulous-style particle effects system. Source code is available from GitHub. A very brief tutorial on its usage by Frozen Sand (creators of Urban Terror) is also available. But in fact "Quake 3 Arena has no support for 'real' particle systems. This program emulates them by using shader FX."[1] Indeed, the quake3world.com forum post speaks of exporting to a .shader.
