Good Building Practices

Physics Optimization:

The less the physics engine has to calculate, the smoother your region will perform. Creating clean low poly physics shapes for your meshes is helpful, but you can also remove prim, mesh, and sculpted objects from the physics calculations completely.

• 
  Two trees set to Prim
• 
  Physical shape of trees
• 
  Results in the navmesh

Link your complicated geometry to simple shapes. Here we linked to a cube and set all child prims to physics shape type None (in Edit > Features > Physics Shape Type):

• 
  No physics on trees
• 
  Navmesh sees only cube set to Prim

To simulate a physics shape and keep avatars from walking through your optimized object, just add physics where it's needed.

• 
  Adding physics
• 
  As seen by physics engine
• 
  As seen by the navmesh

Use the following script to set all child prims to None. Be sure to check what physics are needed for your linkset prior to using, and/or add a simple cube as the root prim. <lsl> default {

   state_entry()
   {
       llShout(0, "Setting all child prims to PRIM_PHYSICS_SHAPE_NONE");
       llSetLinkPrimitiveParamsFast(LINK_ALL_CHILDREN, [PRIM_PHYSICS_SHAPE_TYPE, PRIM_PHYSICS_SHAPE_NONE]);
       llRemoveInventory(llGetScriptName());
   }

} </lsl>