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LSL Concept Overview

(1/3 done - feel free to add stuff, but keep it terse)

Linden Scripting Language (LSL)


One or more scripts can be included in the inventory of a prim to affect its appearance and behavior when it is rezzed in the world.

The script language has familiar operators flow control, and data types including the integer, float, string, and list. There are also a few types specific to SL. A key is a string used to identify objects. A vector is used to represent color, direction, velocity, force, impulse, position, scale, and Euler rotation. Quaterion rotation is used in many cases.

Scripts use constants, define and use local and global variables, user defined functions, and states. A large library of built-in functions provides access to things in SecondLife.

Scripts can handle many kinds of events:

(objects) changed, sensor, collision, on_rez
(agents/avatars) attach, touch, control, money, run_time_permissions
(communication) listen, email, remote_data, dataserver
(world) timer

After being compiled into bytecode, scripts are initially in the default state. Scripts can change the state to any locally defined state or back to the default state. A state change clears all pending events. Resetting a script not only resets the state to the default state, but also resets all global variables to their initial state.

Scripts can be turned on or off by another script in the same prim with llSetScriptState.
Scripts can be updated by other scripts with llRemoteLoadScriptPin.
Some functions cause a ScriptDelay after executing.

memory | errors


The SL world or grid consists of several sims positioned in cartesian global coordinates each one with its own regional coordinates. Each prim and object has its own own internal local coordinates.

Sims always have land, but may be submerged in water.


Agents and Avatars

A user is represented by an agent and an avatar. An agent can be an object, creator and/or owner. Three or more users can form a group and own land and group objects.

The user controls an avatar, a visual representation of a user agent, via the client program. The avatar always plays an animation. An avatar can have attachments to parts of its body.


An object is composed of a non-hierarchical set of prims or primitive shapes that are linked together.

Each prim has a shape composed of several sides. Each side has a color, opacity, and texture.
Each prim has geometric properties position, scale, and rotation, and several additional parameters Particles

Objects (but not prims) have permissions which constrain what users, avatars, and other objects can do with them.
An object is either solid or phantom, and it either obeys physics or not.
When an object is rezzed it may be permanent or TemporaryOnRez.

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