Pathfinding is drawing closer to a release across the main grid, and preparation work for the roll-out – which will constitute one of the biggest changes to SL – is underway on several fronts. This article is intended to be a high-level update on various elements of the project, gleaned from a variety of sources.

Magnum RC Roll-out

On Wednesday July 11th, the server-side pathfinding code was rolled-out to the Magnum Release Channel. There had been some predictions that this could lead to significant problems and issues as a result of the issues given within the release notes

Following the release, issues were experienced, notably with mesh vehicles, as reported on the forum thread discussing the releases for the week, and which have been rapidly responded to by Linden Lab personnel. there are still concerns around the roll-out and potential impact, and Linden Lab are continuing to monitor.

In discussing the RC toll-out at the TPV/Developer meeting held on Friday July 13th, Lorca Linden, the Associate Producer responsible for the project, commented: “OK, so pathfinding did go in RC on Magnum on Wednesday [July 11th]. As a whole, things are looking really, really good. We’re seeing very few crashes, the performance is working great we are seeing issues with some vehicles – definitely not all. That’s the only major hitch that we’re looking into, but as a whole the RC has been going quite smoothly.”

New Viewer Tools

As mentioned above, Lorca Linden (together with Stinson Linden and Prep Linden) from the pathfinding project attended the Friday TPV/Developer meeting on the 13th July, where they specifically discussed the viewer-side pathfinding tools. The tools are covered in detail in a new wiki page from Linden Lab, and may already be familiar to those who have been working on the pathfinding beta. They are currently in the Pathfinding Project Viewer, and will need to be incorporated in to TPVs as well. The wiki page provides comprehensive notes on the tools, complete with screen shots; the following in intended to provide a high-level summary and some background notes for those unfamiliar with the core elements of pathfinding, and to provide an overview of what this means for viewers going forward.

Navmesh and the Rebake Tool

For those not familiar with the term, navmesh is short for navigation mesh. This is a representation of a region’s geometry generated and used by the physics simulator to determine paths for pathfinding characters. The navmesh can be somewhat fluid in nature, depending upon what is going on in a region and what is being changed; a new path for a character, for example, will change a region’s navmesh. When this happens, the navmesh for the region needs to be updated, which can take some six hours  if left to update automatically.

To overcome this when pathfinding is rolled out, one of the new tools that will be appearing in the viewer will be a Rebake Region button. This will automatically appear at the bottom of the viewer window of all users within a region when the navmesh requires updating – regardless as to who may actually have altered the navmesh.

Once baking has commenced, the button will fade on all viewers on which is displayed, indicating that an update is in progress (and preventing someone else from initiating a rebake). Once the rebake is complete and the navmesh is updated, the button will vanish from viewers.

Object Attribute Tools

By default, a navmesh treats all resident-made objects within the region in which it is active as obstacles that pathfinding characters must manoeuvre around. Obviously, this may not always be the case; there will be objects (e.g. stairs, ramps, sidewalks, floors, etc.), pathfinding characters need to traverse, climb, etc. This is achieved by altering the pathfinding atrributes associated with an object, and some of the new viewer tools are to allow this to be done and to also allow users to examine in-world objects to determine their status vis-a-vis pathfinding and how pathfinding characters will react to them.

These tools take the form of menu options and additional panels located in the Build and Object Profile floaters.

Dedicated Floaters

Also included in the tools are three dedicated pathfinding floater panels:

• Linsket floater: designed to give advanced users and builders the ability to customize an area to achieve interesting effects with pathfinding-enabled characters
• Character floater: designed primarily to help users to locate characters moving throughout a region and to identify the CPU cost of characters affecting the performance of a region
• View / Test floater: intended for advanced users who are building pathfinding-enabled objects and characters.

Tool Status and TPV Integration

As mentioned above, these tools are all currently available in a Project Viewer. However, it is anticipated that they will be appearing in a Linden Lab beta viewer in “one to two weeks” (Lorca Linden). The tools themselves are regarded as feature complete by LL, and Lorca encouraged TPV developers at the meeting to consider integrating them into their viewers sooner rather than later.

Integrating the new tools in TPVs is liable to be in two parts:

• An initial release containing the tools required for setting object attributes, etc.
• A follow-up release incorporating the use of the Havok libraries Linden Lab is establishing and which will be made available under the new sub-licence arrangement.

The reasons for this are two-fold:

• The attribute tools, etc., are vital for optimising pathfinding within regions and ensuring everything works correctly (e.g. to ensure pathfinding characters can climb the stairs they’re supposed to by climbing or walk along the prim sidewalk they are supposed to walk along, etc.
• The Havok libraries are not yet available, although Oz hopes to have them in a position where he can talk in more detail to TPVs about them “pretty soon”, and while it is nice to be able to visualise the navmesh, etc., it is not quite such vital part of the pathfinding process.

Universal Tools

Alongside the viewer tools, pathfinding will see a set of universal tools rolled-out in console format. These will be available to region owners and estate managers and will allow them to change an entire class of object in a region to have certain pathfinding attributes once pathfinding goes live. Linden Lab are approaching this in terms of having all non-scripted objects set them to be static obstacles that pathfinding characters must manoeuvre around, while anything that is scripted is set to “dynamic”, as it is thought to be moving.

This obviously doesn’t fit all cases – vendor boards, for example are scripted, but they are hardly what can be termed “moving” objects. Indeed, it might be argued that the majority of scripted objects within a region are non-moving, and therefore should have their pathfinding attribute set to “static”. However, LL feel they have no way of easily differentiating between a non-moving scripted object and a moving scripted object, and thus feel that setting all scripted objects to “dynamic” is the better option and allowing the attribute to then be modified through the viewer where necessary, as setting them to “static” could result in a worse overall behaviour case within a region.

Other Tools and Items

Alongside the above, Linden Lab have previously indicated that they will be making the following available as pathfinding rolls-out:

• A set of script templates used for the creatures found in the Wilderness areas
• A script for a “master rezzer system”.

The latter is a means by which region performance and the number of pathfinding characters rezzed in the region can be monitored, and which will reduce the number of pathfinding characters within a region in response to the region’s performance / number of avatars within the region.

Potential Timescales for Roll-out

During the TPV/Developer’s meeting, Lorca outlined some potential dates for pathfinding. note that these are currently potential, and shouldn’t be taken as tablets of stone:

• The pathfinding tools should be available in one to two weeks in a beta viewer
• The server-side release is dependent upon how well (or otherwise) the current release to the Magnum RC progresses, and may potentially come within the next two-to-four weeks, but certainly no sooner than two weeks.

Again these are not confirmed dates, and may well change in the next couple of weeks – particularly if major issues are found with the Magnum RC roll-out.

Related Links

• good building practices
• viewer pathfinding tools – SL wiki
• Audio recording of the TPV/Developer meeting