Pathfinding in Second Life

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Overview

At a high level, pathfinding provides tools and functions to enable smoother and smarter movement behavior for non-avatar entities in Second Life (for example, monsters in a game, rats in a haunted house, wisps in a fantasy forest). We refer to these entities as characters; in gaming terminology, they are sometimes called NPCs (non-player characters) or mobs (mobile objects).

Up till now, content creators had to use resource-intensive scripting workarounds to emulate intelligent character movement. With the addition of pathfinding, content creators will have a much easier and better performing way of creating characters that can move around in the world. Characters can use LSL functions to avoid obstacles, move around corners, climb inclines, and move across region boundaries: things that are very difficult or even impossible before. Pathfinding will also enable new gameplay mechanics, such as creating food that attracts monsters.

KBnote.png Note: Pathfinding is not an animation system. It does not provide a way to animate a biped or quadruped in conjunction with the new movement functionality. You must use existing methods to animate characters. Nevertheless, pathfinding enables more dynamic movement and provides a better system for controlling character movement than was previously possible. For more information on creating animations, see Animation.

LSL functions

The pathfinding LSL functions enable you to create characters that dynamically avoid obstacles while performing typical behaviors you might want in a game or other virtual experience, including:

  • Evade - run away from a specified object or avatar. See llEvade.
  • Flee - Attempt to get a specified distance from a specified location. See llFleeFrom.
  • Navigate - Move to a specific location. See llNavigateTo.
  • Patrol - Move through a path defined by a set of "patrol points." See llPatrolPoints.
  • Pursue - Chase a specified object or avatar. See llPursue.
  • Wander - Randomly move around a specified distance from a specified central point. See llWanderWithin.

Alpha release information

Pathfinding API documentation

LSL reference

Pathfinding functions

  • llCreateCharacter - Convert the current linkset to an AI character. By default, the character's shape will be an upright capsule approximately the size of the linkset, adjustable via the options list. The linkset must use mesh accounting.
  • llDeleteCharacter - Convert the current linkset back to a standard object
  • llEvade - Causes the character to keep away from the object or avatar identified by the key.
  • llExecCharacterCmd - Send a command to the pathing system.
  • llFleeFrom - Attempt to get at least 'distance' away from 'source' - provided in region-local coordinates.
  • llGetClosestNavPoint - Accepts a point in region-local space and returns either an empty list or a list containing a single vector which is the closest point on the navmesh to the point provided.
  • llNavigateTo - Navigate to a destination provided in region coordinates. The destination may be in another region.
  • llPatrolPoints - Patrol a provided set of points provided as vectors.
  • llPursue - Causes the character to chase after the object or avatar identified by the key.
  • llUpdateCharacter - Update character properties.
  • llWanderWithin - Wander within an area approximately 'scale' in radius centered at 'origin'. Wandering means choosing a random point in the area and navigating to it. After arrival, a new random point will be chosen and navigated to.

Pathfinding events

  • path_update - Informs the script of events that happen within the pathfinding system.