Linkset Physics and Limitations

v7 beta documentation in progress. v7 beta documentation may be incomplete or inaccurate.
v7 functions and features may be significantly different from previous ACS versions.


There are two types of linksets supported by SL in vehicles.

These two types are described here as Mesh Linkset or Legacy Linkset.

Mesh Linkset is used by any vehicle that uses mesh, or has over 32 links.

Legacy Linkset is any vehicle 32 prims or less that does not contain mesh, only regular prims or sculpties. Before the introduction of mesh to SL, all vehicles were in this category. (Higher prim vehicles had to use special attachments to bypass this limitation).


Mesh Linkset Limitations

These can be slightly tricky to understand at first, as they aren't really properly documented anywhere, but once you get a grasp of how it works, you can often significantly reduce LI for your entire vehicle by using a few tricks.

In a mesh linkset, prims are assigned either the CONVEX HULL shape (aka solid), or the NONE shape. Links that are CONVEX HULL act as solid objects that will not pass through other prims or land. These prims also contribute weight and mass to the linkset. The root prim is always CONVEX HULL in a mesh linkset.

Links that are set to NONE shape are sort of phantom. They will pass through other prims, and contribute no weight or mass to the vehicle.

At a minimum, a vehicle requires at least tires to be CONVEX_HULL so that the vehicle will drive on top of land or prim roads.

SL imposes a limit of 32 LI for any CONVEX HULL prims in an entire linkset, however there does not appear to be an LI limit for the entire linkset (including the NONE-shaped links), just the maximum limit of 255 links.

You can determine CONVEX HULL LI by checking the LI of a prim unlinked.

The ACS automated system sets up prim shapes by keyword. The root prim automatically is CONVEX HULL, but beyond that any prim with solid, wheel, or tire in the name, ACS will set to CONVEX HULL shape, and all other prims are set to NONE shape.

Some builders prefer to set their prim shapes by hand, and you can disable ACS's automatic prim shape setting by changing ManualPrimShapes to TRUE in the Root Settings script.

The number of links in a Mesh Linkset vehicle can be up to 256, the maximum number of links in any SL object.

Legacy Linksets

"Legacy" style linksets (non-mesh, 32 prims or less) have worthwhile advantages and many builders still use this style.

All prims are "solid" in the link set and count as 1 LI each no matter the complexity of the sculpt. This makes the vehicle far less likely to get caught on edges and walls, so can be preferred for high-speed racing. Each prim in the linkset has weight and mass which makes the vehicle interact with SL physics in preferable ways.

The limitation of low prim counts and single face prims make loading textures and prims for a vehicle much faster, as well as easier region crossings with less assets to hand off to the next region.