Mesh Physics / High Prim Mode
If you were not aware, new mesh controls allow a special physics mode that lets you use a higher prim count than 32 for vehicles up to a certain point. Previously this was achieved simply by manually setting parameters on the prims in certain newer viewers, or by dropping in the old KCP Over32 script which sets up the vehicle automatically and is not viewer dependent.

Prim counts are still limited based on physics parameters of the prims, you will need some set to a special solid mode (convex hull) as to not sink into the ground, but the more prims set to solid the less free physics cost you have for additional prims.

  • v5.1/v6 integrates the KCP Over32 prim script in the regular root prim scripts, so no additional setup script is needed and it will kick in automatically if you exceed 32 prims.
  • If you link more than 32 prims into the vehicle it will automatically use the special mesh/high prim mode.
  • This will automatically set all prims you have labelled with the solid keywords as well as any prims with wheel or tire in the name to solid/convex hull, required as to not sink into the ground.
  • If you unlink back to 32 prims or less, it will revert the prim physics back to standard prim style.
  • The vehicle will report how much physics costs you are using. Setting prims to solid/convex hull uses up your physics cost, which is why you want as few prims set to solid as possible. On bikes, the frame is a good candidate for solid as its sculpt bounding box will cover much of the vehicle as solid (Also for bikes, consider an invisible elongated half sphere shield prim acting as a physics sled around the bottom of the vehicle, while leaving the top clear so driver and passengers can still properly select sit target prims)
  • If you don't link over 32 prims, the mode will not engage and you don't have to worry about it.

The old Over32 script is included in the v5.1 box for use in your older scripted vehicles. You no longer need to add the Over32 script if using v5.1.

You must have components that touch the ground set to solid via keyword (solid, tire, or wheel) or the vehicle will sink into the ground.

After renaming prims with keywords, be sure to reboot the vehicle so it can scan and detect the prims.

Disable/Override

If you have LESS than 32 individual prims total, regardless of the land impact value, but are using mesh, you will need to force on high prim mode.

At the top of the Root Settings script you can set a value to disable or force on the high prim/new physics mode:

integer         AutoOver32  =      0; //Leave at 0 for most cases.

The default setting is 0. High prim physics mode kicks in automatically for over 32 prims
Set to 1 to force OFF the automatic new physics for any prim count, for setting up prims manually.
Set to 2 to force ON the new mesh physics, even for less than 32 prims. (may exceed vehicle physics limit by using new physics on less than 32 prims)

How many prims can I use?

In theory you can use up to 255 individual prims as some have set up, but in reality you will probably want to use less. The new SL method of calculating prim cost equivalent for a physical vehicle depends greatly on the complexity of any mesh parts, and how many prims are set to solid/convex hull mode, and not literally by number of prims. For traditional sculpty-based bikes with some solid parts (tires, frame) you may be able to comfortably fit 60-80 prims. As you link in each new prim, the scripts will announce how much allotment is left. If you go over the count, the script will generate errors when you try to operate the vehicle. You can also choose to disable the automatic physics settings in the scripts and set them manually with your newer viewer.

Vehicles 32 prims or less are automatically in "traditional" prim mode, all parts solid.

Keep in mind that the more parts your vehicle has, the longer it will take to load for anyone else present. Your 255 prim monster truck may look great, but in reality, when you rez it it will be forcing everybody nearby to load every part and texture. Imagine how your favorite vehicle sim would suffer greatly if everyone there was driving 100+ prim vehicles. Those who purchase your vehicles are going to be far less likely to leave them parked on display the more prims they have. You should indeed take advantage of the ability to add more prims than 32, but be reasonable. It's far more realistic now to be able to add extra details like individual turning indicators that previously would have been left out of a build, but going overboard with prims can actually negatively impact the usability of the vehicle even if it technically can support the prim count/cost.