For clouds, use a RNG seed that only changes every 10 minutes.

This allows multi-process deploymentes to keep their clouds in sync.

diff --git a/simgear/math/sg_random.c b/simgear/math/sg_random.c
index e9004323b2fa93f7d5744005fa71abefb9b70088..d9f6bcb78f9c8642abc3ab32c2c807cd370e00e1 100644 (file)
--- a/simgear/math/sg_random.c
+++ b/simgear/math/sg_random.c
@@ -59,6 +59,11 @@ void mt_init(mt *mt, unsigned int seed)
     mt->index = MT_N+1;
 }
 
+void mt_init_time_10(mt *mt)
+{
+  mt_init(mt, (unsigned int) time(NULL) / 600);  
+}
+
 unsigned int mt_rand32(mt *mt)
 {
     unsigned int i, y;

diff --git a/simgear/math/sg_random.h b/simgear/math/sg_random.h
index 51fefb65001d71f596af3f62ea1968764fc899c9..aa084a6362439b50063ec9a94bd6ab8552bc8fb5 100644 (file)
--- a/simgear/math/sg_random.h
+++ b/simgear/math/sg_random.h
@@ -47,6 +47,13 @@ typedef struct {unsigned int array[MT_N]; int index; } mt;
  */
 void mt_init(mt *mt, unsigned int seed);
 
+/**
+ * Initialize a new MT state with a seed that only
+ * changes every 10 minutes.  Used to synchronize
+ * multi-process deployments.
+ */
+void mt_init_time_10(mt *mt);
+
 /**
  * Generate a new 32-bit random number based on the given MT state.
  */

diff --git a/simgear/scene/sky/CloudShaderGeometry.hxx b/simgear/scene/sky/CloudShaderGeometry.hxx
index 3825c843b7d4ac69cd36ab072a2eac0a0b6ef32e..20d0db8172d4d68be3fb43042b495757d63eb5b6 100644 (file)
--- a/simgear/scene/sky/CloudShaderGeometry.hxx
+++ b/simgear/scene/sky/CloudShaderGeometry.hxx
@@ -46,7 +46,7 @@ class CloudShaderGeometry : public osg::Drawable
         
         const static unsigned int USR_ATTR_1 = 10;
         const static unsigned int USR_ATTR_2 = 11;
-        const static unsigned int USR_ATTR_3 = 12;
+        const static unsigned int USR_ATTR_3 = 12;        
                 
         CloudShaderGeometry()
         { 

diff --git a/simgear/scene/sky/cloud.cxx b/simgear/scene/sky/cloud.cxx
index 5517cff9ac2c754c0fe7f7cac752fad84acc54d5..3558cac90a01c489d7db12c5e4594e06a81081f6 100644 (file)
--- a/simgear/scene/sky/cloud.cxx
+++ b/simgear/scene/sky/cloud.cxx
@@ -194,7 +194,10 @@ SGCloudLayer::SGCloudLayer( const string &tex_path ) :
                                        ->getWhiteTexture(),
                                        osg::StateAttribute::ON);
   rootSet->setDataVariance(osg::Object::DYNAMIC);
-
+  
+  // Ensure repeatability of the random seed within 10 minutes,
+  // to keep multi-computer systems in sync.
+  sg_srandom_time_10();
   base = osg::Vec2(sg_random(), sg_random());
   group_top->addChild(layer_transform.get());
   group_bottom->addChild(layer_transform.get());

diff --git a/simgear/scene/sky/newcloud.cxx b/simgear/scene/sky/newcloud.cxx
index 4632347edb32754a58cc4ab1bafe6e2c634aa3d8..503e1de740e83e9e23386d4312374460e0d2b957 100644 (file)
--- a/simgear/scene/sky/newcloud.cxx
+++ b/simgear/scene/sky/newcloud.cxx
@@ -40,7 +40,6 @@
 
 #include <simgear/compiler.h>
 
-#include <simgear/math/sg_random.h>
 #include <simgear/misc/sg_path.hxx>
 #include <simgear/props/props.hxx>
 #include <simgear/scene/model/model.hxx>
@@ -73,6 +72,10 @@ float SGNewCloud::sprite_density = 1.0;
 
 SGNewCloud::SGNewCloud(const SGPath &texture_root, const SGPropertyNode *cld_def)
 {
+    // Set up a RNG that is repeatable within 10 minutes to ensure that clouds
+    // are synced up in multi-process deployments.
+    mt_init_time_10(&seed);
+  
     min_width = cld_def->getFloatValue("min-cloud-width-m", 500.0);
     max_width = cld_def->getFloatValue("max-cloud-width-m", min_width*2);
     min_height = cld_def->getFloatValue("min-cloud-height-m", 400.0);
@@ -132,7 +135,7 @@ SGNewCloud::~SGNewCloud() {
 #if 0
 // return a random number between -n/2 and n/2, tending to 0
 static float Rnd(float n) {
-    return n * (-0.5f + (sg_random() + sg_random()) / 2.0f);
+    return n * (-0.5f + (mt_rand(&seed) + mt_rand(&seed)) / 2.0f);
 }
 #endif
 
@@ -143,17 +146,17 @@ osg::ref_ptr<EffectGeode> SGNewCloud::genCloud() {
     // Determine how big this specific cloud instance is. Note that we subtract
     // the sprite size because the width/height is used to define the limits of
     // the center of the sprites, not their edges.
-    float width = min_width + sg_random() * (max_width - min_width) - min_sprite_width;
-    float height = min_height + sg_random() * (max_height - min_height) - min_sprite_height;
+    float width = min_width + mt_rand(&seed) * (max_width - min_width) - min_sprite_width;
+    float height = min_height + mt_rand(&seed) * (max_height - min_height) - min_sprite_height;
     
     if (width  < 0.0) { width  = 0.0; }
     if (height < 0.0) { height = 0.0; }
     
     // Determine appropriate shading factors
-    float top_factor = min_top_lighting_factor + sg_random() * (max_top_lighting_factor - min_top_lighting_factor);
-    float middle_factor = min_middle_lighting_factor + sg_random() * (max_middle_lighting_factor - min_middle_lighting_factor);
-    float bottom_factor = min_bottom_lighting_factor + sg_random() * (max_bottom_lighting_factor - min_bottom_lighting_factor);
-    float shade_factor = min_shade_lighting_factor + sg_random() * (max_shade_lighting_factor - min_shade_lighting_factor);
+    float top_factor = min_top_lighting_factor + mt_rand(&seed) * (max_top_lighting_factor - min_top_lighting_factor);
+    float middle_factor = min_middle_lighting_factor + mt_rand(&seed) * (max_middle_lighting_factor - min_middle_lighting_factor);
+    float bottom_factor = min_bottom_lighting_factor + mt_rand(&seed) * (max_bottom_lighting_factor - min_bottom_lighting_factor);
+    float shade_factor = min_shade_lighting_factor + mt_rand(&seed) * (max_shade_lighting_factor - min_shade_lighting_factor);
     
     //printf("Cloud: %2f, %2f, %2f, %2f\n", top_factor, middle_factor, bottom_factor, shade_factor); 
     
@@ -173,7 +176,7 @@ osg::ref_ptr<EffectGeode> SGNewCloud::genCloud() {
     float cull_distance_squared = min_sprite_height * min_sprite_height * 0.1f;
     
     // The number of sprites we actually use is a function of the (user-controlled) density
-    int n_sprites = num_sprites * sprite_density * (0.5f + sg_random());
+    int n_sprites = num_sprites * sprite_density * (0.5f + mt_rand(&seed));
     
     for (int i = 0; i < n_sprites; i++)
     {
@@ -191,16 +194,16 @@ osg::ref_ptr<EffectGeode> SGNewCloud::genCloud() {
             y = 0;
             z = height * 0.5;
         } else {
-            float theta = sg_random() * SGD_2PI;
-            float elev  = sg_random() * SGD_PI;
+            float theta = mt_rand(&seed) * SGD_2PI;
+            float elev  = mt_rand(&seed) * SGD_PI;
             x = width * cos(theta) * 0.5f * sin(elev);
             y = width * sin(theta) * 0.5f * sin(elev);
             z = height * cos(elev) * 0.5f + height * 0.5f;
         }
         
         // Determine the height and width
-        float sprite_width = min_sprite_width + sg_random() * (max_sprite_width - min_sprite_width);
-        float sprite_height = min_sprite_height + sg_random() * (max_sprite_height - min_sprite_height);
+        float sprite_width = min_sprite_width + mt_rand(&seed) * (max_sprite_width - min_sprite_width);
+        float sprite_height = min_sprite_height + mt_rand(&seed) * (max_sprite_height - min_sprite_height);
         
         // Sprites are never taller than square.
         if (sprite_height > sprite_width )
@@ -223,10 +226,10 @@ osg::ref_ptr<EffectGeode> SGNewCloud::genCloud() {
         }        
 
         // Determine the sprite texture indexes.
-        int index_x = (int) floor(sg_random() * num_textures_x);
+        int index_x = (int) floor(mt_rand(&seed) * num_textures_x);
         if (index_x >= num_textures_x) { index_x = num_textures_x - 1; }
                 
-        int index_y = (int) floor(sg_random() * num_textures_y);
+        int index_y = (int) floor(mt_rand(&seed) * num_textures_y);
         
         if (height_map_texture) {
           // The y index depends on the position of the sprite within the cloud.

diff --git a/simgear/scene/sky/newcloud.hxx b/simgear/scene/sky/newcloud.hxx
index 1f207d412a7d89c66fa165444c8c1a2ae76af3fd..fd7c905a295359f2d5ec5886c77397334aa64d77 100644 (file)
--- a/simgear/scene/sky/newcloud.hxx
+++ b/simgear/scene/sky/newcloud.hxx
@@ -28,6 +28,7 @@
 #include <vector>
 #include <osg/Fog>
 
+#include <simgear/math/sg_random.h>
 #include <simgear/scene/material/Effect.hxx>
 #include <simgear/scene/material/EffectGeode.hxx>
 
@@ -100,6 +101,9 @@ private:
         osg::Geometry* quad;
         osg::ref_ptr<simgear::Effect> effect;
         static float sprite_density;
+        
+        // RNG seed for this cloud
+        mt seed;
 
         osg::Geometry* createOrthQuad(float w, float h, int varieties_x, int varieties_y);
 };

diff --git a/simgear/scene/sky/sky.cxx b/simgear/scene/sky/sky.cxx
index a096facb5d9c21ab01d6849c4b75b5b165e99834..ce3ceb699253a1a4e7aaa895bb93df9af958ebad 100644 (file)
--- a/simgear/scene/sky/sky.cxx
+++ b/simgear/scene/sky/sky.cxx
@@ -29,7 +29,6 @@
 #include "cloudfield.hxx"
 #include "newcloud.hxx"
 
-#include <simgear/math/sg_random.h>
 #include <simgear/scene/util/RenderConstants.hxx>
 #include <simgear/scene/util/OsgMath.hxx>
 #include <simgear/sg_inlines.h>
@@ -68,6 +67,10 @@ SGSky::SGSky( void ) {
     pre_transform = new osg::Group;
 
     _ephTransform = new osg::MatrixTransform;
+    
+    // Set up a RNG that is repeatable within 10 minutes to ensure that clouds
+    // are synced up in multi-process deployments.
+    mt_init_time_10(&seed);
 }
 
 
@@ -373,11 +376,11 @@ void SGSky::modify_vis( float alt, float time_factor ) {
        if ( ratio < 1.0 ) {
            if ( ! in_puff ) {
                // calc chance of entering cloud puff
-               double rnd = sg_random();
+               double rnd = mt_rand(&seed);
                double chance = rnd * rnd * rnd;
                if ( chance > 0.95 /* * (diff - 25) / 50.0 */ ) {
                    in_puff = true;
-                   puff_length = sg_random() * 2.0; // up to 2 seconds
+                   puff_length = mt_rand(&seed) * 2.0; // up to 2 seconds
                    puff_progression = 0.0;
                }
            }

diff --git a/simgear/scene/sky/sky.hxx b/simgear/scene/sky/sky.hxx
index d9079bc1aa979b91adb2378621a0f30e50621508..cc9c191e70769f33ef671e0acf5b98e3a92ecd64 100644 (file)
--- a/simgear/scene/sky/sky.hxx
+++ b/simgear/scene/sky/sky.hxx
@@ -34,6 +34,7 @@
 #endif
 
 #include <simgear/compiler.h>
+#include <simgear/math/sg_random.h>
 #include <simgear/misc/sg_path.hxx>
 #include <simgear/props/props.hxx>
 
@@ -250,6 +251,9 @@ private:
 
     // 3D cloud density
     double clouds_3d_density;
+    
+    // RNG seed
+    mt seed;
 
 public: