BulletSim

BulletSim

BulletSim is the module for OpenSimulator that creates virtual world physics using the Bullet Physics Engine. This module will provide high performance physics as well as physical vehicle performance compatible with Second Life.

Project Information

BulletSim/Functionality lists the possible physical operations, their implementation state and any notes on their use. This is particularly useful for vehicle operations.

"Actor" Architecture

Each BulletSim physical object can have any number of "actors" attached to it. The actors register for simulation events (usually to be called before each simulation step) and change the physical parameters of the object. The currently implemented actors are:

• BSActorAvatarMove: controls movement and stairs walking of avatars;
• BSActorHover: implements vertical hovering for objects and avatars;
• BSActorLockAxis: applies a constraint to physical objects to lock one or more angular axis movement;
• BSActorMoveToTarget: moves a physical object to a location;
• BSActorSetForce: applies a continuous force to a physical object;
• BSActorSetTorque: applies a continuous torque to a physical object;
• BSDynamic (name will change): implements SecondLife(r) vehicle model.

Avatar Walking Up Stairs

The avatar movement actor include special checks to allow avatars to move up stepped objects (think stairs). The code works by checking for collisions close to the avatar's feet and, if trying to walk forward and not flying, pushing the avatar up to get over the object. This is a different algorithm than ODE which relies on the curvature of the avatar's capsule to move up and over low obstacles.

There are five INI parameters that control stairs:

[BulletSim]
    AvatarStepHeight = 0.5
    AvatarStepApproachFactor = 0.6
    AvatarStepUpCorrectionFactor = 1.0
    AvatarStepForceFactor = 1.0
    AvatarStepSmoothingSteps = 2