Add "is_plantation" property to materials definitions.

simgear/scene/material/mat.cxx

@@ -328,6 +328,7 @@ SGMaterial::read_properties(const SGReaderWriterOptions* options,
         
     // Random vegetation properties
     wood_coverage = props->getDoubleValue("wood-coverage", 0.0);
+    is_plantation = props->getBoolValue("plantation",false);
     tree_effect = props->getStringValue("tree-effect", "Effects/tree");
     tree_height = props->getDoubleValue("tree-height-m", 0.0);
     tree_width = props->getDoubleValue("tree-width-m", 0.0);

simgear/scene/material/mat.hxx

@@ -244,6 +244,13 @@ public:
    */
   inline double get_wood_coverage () const { return wood_coverage; }
 
+  /**
+   * Get whether or not vegetation is regularly spaced
+   *
+   * @return flag: if true, vegetation is regularly spaced.
+   */
+  inline bool get_is_plantation () const { return is_plantation; }
+
   /**
    * Get the tree height.
    *
@@ -455,6 +462,9 @@ private:
   // coverage of woods
   double wood_coverage;
 
+  // are trees regularly planted?
+  bool is_plantation;
+
   // Range at which trees become visible
   double tree_range;