Section 2.2.5 rdInstBase- Instancing – Per-Instance Custom Data
// [rdInst v1.24] Gets a reference to the Per-Instance CustomData for the mesh
TArray<float>& rdGetCustomDataPtr(UStaticMesh* mesh,int32& numData);
// [rdInst v1.24] Sets a value to the Per-Instance CustomData for the mesh
void rdSetCustomData(UStaticMesh* mesh,int32 instanceIndex,int32 dataIndex,float value);
// [rdInst v1.24] Updates the Per-Instance CustomData for the mesh
void rdUpdateCustomData(UStaticMesh* mesh);