Sims 3:0x02019972

MTST

This is a Sims_3:RCOL chunk.

   DWORD // 'MTST'
   DWORD // version?
   DWORD // unknown
   DWORD // (initial MATD index) | 0x10000000;
   DWORD // count

repeat count times:

   DWORD // (MATD index) | 0x10000000
   DWORD // MATD's hash name

Postulate based MTST blocks encountered so far (Needs Confirmation!):

All MTST blocks have a count >= 1 and the following block in the repetition section:

   DWORD // (MATD index = initial MATD index) | 0x10000000
   DWORD // 0x2EA8FB98 (fnv32 hash of "Default")

The purpose of the MTST is to allow multiple material definitions to be swapped by the game through the function:

   ScriptCore.World.ObjectSetMaterial(ObjectGuid objId, string materialSetName, float transitionTime, bool bTransitionToOverlay);

For most objects, this function is often accessed through the function:

   Sims3.Gameplay.Abstracts.GameObject.SetMaterial(string materialSetName);

The string argument is fnv32 hashed and matched with the hash name to locate and swap out the object's material.