+ double get_friction_factor () const { return friction_factor; }
+
+ /**
+ * Get the rolling friction for that material
+ */
+ double get_rolling_friction () const { return rolling_friction; }
+
+ /**
+ * Get the bumpines for that material
+ */
+ double get_bumpiness () const { return bumpiness; }
+
+ /**
+ * Get the load resistance
+ */
+ double get_load_resistance () const { return load_resistance; }
+
+ /**
+ * Get the list of names for this material
+ */
+ const std::vector<std::string>& get_names() const { return _names; }
+
+ /**
+ * add the given name to the list of names this material is known
+ */
+ void add_name(const std::string& name) { _names.push_back(name); }
+
+ /**
+ * Get the number of randomly-placed objects defined for this material.
+ */
+ int get_object_group_count () const { return object_groups.size(); }
+
+ /**
+ * Get a randomly-placed object for this material.
+ */
+ SGMatModelGroup * get_object_group (int index) const {
+ return object_groups[index];
+ }