From 68797e51c66d44d9a3178b659c9f970d996796e1 Mon Sep 17 00:00:00 2001
From: ehofman <ehofman>
Date: Mon, 1 Feb 2010 10:05:14 +0000
Subject: [PATCH 1/2] implement a round-robin scheme for random objects to make
 sure the same type of object is placed at the same spot all the time

---
 simgear/scene/material/matmodel.cxx | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/simgear/scene/material/matmodel.cxx b/simgear/scene/material/matmodel.cxx
index bdad512e..c625d9b0 100644
--- a/simgear/scene/material/matmodel.cxx
+++ b/simgear/scene/material/matmodel.cxx
@@ -139,8 +139,9 @@ SGMatModel::get_random_model( SGPropertyNode *prop_root )
 {
   load_models( prop_root ); // comment this out if preloading models
   int nModels = _models.size();
-  int index = int(sg_random() * nModels);
-  if (index >= nModels)
+  // int index = int(sg_random() * nModels);
+  static int index = -1;
+  if (++index >= nModels)
     index = 0;
   return _models[index].get();
 }

From 675c86582d8b25270897db0a36d0e02388f09bf4 Mon Sep 17 00:00:00 2001
From: fredb <fredb>
Date: Sun, 25 Apr 2010 10:47:37 +0000
Subject: [PATCH 2/2] Stuart Buchanan: Fix a bug in the random object placement
 where the model selected in the case of multiple object definitions in
 material.xml was random, rather than seeded.

---
 simgear/scene/material/matmodel.cxx | 8 ++------
 simgear/scene/material/matmodel.hxx | 2 +-
 simgear/scene/tgdb/obj.cxx          | 2 +-
 simgear/scene/tgdb/userdata.cxx     | 4 ++--
 simgear/scene/tgdb/userdata.hxx     | 3 ++-
 5 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/simgear/scene/material/matmodel.cxx b/simgear/scene/material/matmodel.cxx
index c625d9b0..93cbd494 100644
--- a/simgear/scene/material/matmodel.cxx
+++ b/simgear/scene/material/matmodel.cxx
@@ -135,15 +135,11 @@ SGMatModel::load_models( SGPropertyNode *prop_root )
 }
 
 osg::Node*
-SGMatModel::get_random_model( SGPropertyNode *prop_root )
+SGMatModel::get_random_model( SGPropertyNode *prop_root, mt seed )
 {
   load_models( prop_root ); // comment this out if preloading models
   int nModels = _models.size();
-  // int index = int(sg_random() * nModels);
-  static int index = -1;
-  if (++index >= nModels)
-    index = 0;
-  return _models[index].get();
+  return _models[mt_rand(&seed) * nModels].get();
 }
 
 double
diff --git a/simgear/scene/material/matmodel.hxx b/simgear/scene/material/matmodel.hxx
index 9d06427a..3e7d84a9 100644
--- a/simgear/scene/material/matmodel.hxx
+++ b/simgear/scene/material/matmodel.hxx
@@ -82,7 +82,7 @@ public:
      *
      * @return A randomly select model from the variants.
      */
-    osg::Node *get_random_model( SGPropertyNode *prop_root );
+    osg::Node *get_random_model( SGPropertyNode *prop_root, mt seed );
 
 
     /**
diff --git a/simgear/scene/tgdb/obj.cxx b/simgear/scene/tgdb/obj.cxx
index 74b4a071..001cbf71 100644
--- a/simgear/scene/tgdb/obj.cxx
+++ b/simgear/scene/tgdb/obj.cxx
@@ -610,7 +610,7 @@ SGLoadBTG(const std::string& path, SGMaterialLib *matlib, bool calc_lights, bool
              i < tileGeometryBin.randomModels.getNumModels(); i++) {
           SGMatModelBin::MatModel obj
             = tileGeometryBin.randomModels.getMatModel(i);
-          osg::Node* node = sgGetRandomModel(obj.model);
+          osg::Node* node = sgGetRandomModel(obj.model, seed);
         
           // Create a matrix to place the object in the correct
           // location, and then apply the rotation matrix created
diff --git a/simgear/scene/tgdb/userdata.cxx b/simgear/scene/tgdb/userdata.cxx
index 11d69e12..6aa71821 100644
--- a/simgear/scene/tgdb/userdata.cxx
+++ b/simgear/scene/tgdb/userdata.cxx
@@ -60,8 +60,8 @@ void sgUserDataInit( SGPropertyNode *p ) {
     root_props = p;
 }
 
-osg::Node* sgGetRandomModel(SGMatModel *obj) {
-   return obj->get_random_model( root_props );
+osg::Node* sgGetRandomModel(SGMatModel *obj, mt seed) {
+   return obj->get_random_model( root_props, seed );
  }
 
 namespace simgear
diff --git a/simgear/scene/tgdb/userdata.hxx b/simgear/scene/tgdb/userdata.hxx
index ab0a6a55..fa5209e6 100644
--- a/simgear/scene/tgdb/userdata.hxx
+++ b/simgear/scene/tgdb/userdata.hxx
@@ -26,6 +26,7 @@
 #define _SG_USERDATA_HXX
 
 #include <simgear/compiler.h>
+#include <simgear/math/sg_random.h>
 
 #include <osg/Node>
 
@@ -42,7 +43,7 @@ void sgUserDataInit(SGPropertyNode *p);
 /**
  * Get a random model.
  */
-osg::Node* sgGetRandomModel(SGMatModel *obj);
+osg::Node* sgGetRandomModel(SGMatModel *obj, mt seed);
 
 namespace simgear
 {