From 813b518b6f0c3e772fbd521d75106a650e69a084 Mon Sep 17 00:00:00 2001
From: timoore <timoore>
Date: Thu, 4 Oct 2007 20:53:22 +0000
Subject: [PATCH] Don't reset the random texture base when rebuilding a cloud
 layer This fix removes obnoxious visuals (texture jumping) when a cloud layer
 is moved due to a metar update or, more significantly, when switching from
 metar to a scenario. Also, I switched to using a TexMat to displace the cloud
 texture in order to avoid writing the texture array every frame.

---
 simgear/scene/sky/cloud.cxx | 40 +++++++++++++++++++------------------
 simgear/scene/sky/cloud.hxx |  3 ++-
 2 files changed, 23 insertions(+), 20 deletions(-)

diff --git a/simgear/scene/sky/cloud.cxx b/simgear/scene/sky/cloud.cxx
index 0dc6eac3..5ff1b089 100644
--- a/simgear/scene/sky/cloud.cxx
+++ b/simgear/scene/sky/cloud.cxx
@@ -39,6 +39,7 @@
 #include <osg/TexEnv>
 #include <osg/Texture2D>
 #include <osg/TextureCubeMap>
+#include <osg/TexMat>
 
 #include <simgear/math/sg_random.h>
 #include <simgear/debug/logstream.hxx>
@@ -161,6 +162,8 @@ SGCloudLayer::SGCloudLayer( const string &tex_path ) :
   // Force the cloud layers into recursive bins of bin 4.
   osg::StateSet *rootSet = layer_root->getOrCreateStateSet();
   rootSet->setRenderBinDetails(4, "RenderBin");
+  rootSet->setTextureAttribute(0, new osg::TexMat());
+  base = osg::Vec2(sg_random(), sg_random());
 
   group_top->addChild(layer_transform.get());
   group_bottom->addChild(layer_transform.get());
@@ -248,6 +251,17 @@ SGCloudLayer::setCoverage (Coverage coverage)
     }
 }
 
+void
+SGCloudLayer::setTextureOffset(const osg::Vec2& offset)
+{
+    osg::StateAttribute* attr = layer_root->getStateSet()
+        ->getTextureAttribute(0, osg::StateAttribute::TEXMAT);
+    osg::TexMat* texMat = dynamic_cast<osg::TexMat*>(attr);
+    if (!texMat)
+        return;
+    texMat->setMatrix(osg::Matrix::translate(offset[0], offset[1], 0.0));
+}
+
 // build the cloud object
 void
 SGCloudLayer::rebuild()
@@ -422,9 +436,8 @@ SGCloudLayer::rebuild()
 
     scale = 4000.0;
     last_lon = last_lat = -999.0f;
-    
-    base = osg::Vec2(sg_random(), sg_random());
-    
+
+    setTextureOffset(base);
     // build the cloud layer
     const float layer_scale = layer_span / scale;
     const float mpi = SG_PI/4;
@@ -451,7 +464,7 @@ SGCloudLayer::rebuild()
       
       osg::Vec3 vertex(layer_span*(i-2)/2, -layer_span,
                        alt_diff * (sin(i*mpi) - 2));
-      osg::Vec2 tc(base[0] + layer_scale * i/4, base[1]);
+      osg::Vec2 tc(layer_scale * i/4, 0.0f);
       osg::Vec4 color(1.0f, 1.0f, 1.0f, (i == 0) ? 0.0f : 0.15f);
       
       cl[i]->push_back(color);
@@ -461,8 +474,7 @@ SGCloudLayer::rebuild()
       for (int j = 0; j < 4; j++) {
         vertex = osg::Vec3(layer_span*(i-1)/2, layer_span*(j-2)/2,
                            alt_diff * (sin((i+1)*mpi) + sin(j*mpi) - 2));
-        tc = osg::Vec2(base[0] + layer_scale * (i+1)/4,
-                       base[1] + layer_scale * j/4);
+        tc = osg::Vec2(layer_scale * (i+1)/4, layer_scale * j/4);
         color = osg::Vec4(1.0f, 1.0f, 1.0f,
                           ( (j == 0) || (i == 3)) ?  
                           ( (j == 0) && (i == 3)) ? 0.0f : 0.15f : 1.0f );
@@ -473,8 +485,7 @@ SGCloudLayer::rebuild()
         
         vertex = osg::Vec3(layer_span*(i-2)/2, layer_span*(j-1)/2,
                            alt_diff * (sin(i*mpi) + sin((j+1)*mpi) - 2) );
-        tc = osg::Vec2(base[0] + layer_scale * i/4,
-                       base[1] + layer_scale * (j+1)/4 );
+        tc = osg::Vec2(layer_scale * i/4, layer_scale * (j+1)/4 );
         color = osg::Vec4(1.0f, 1.0f, 1.0f,
                           ((j == 3) || (i == 0)) ?
                           ((j == 3) && (i == 0)) ? 0.0f : 0.15f : 1.0f );
@@ -486,8 +497,7 @@ SGCloudLayer::rebuild()
       vertex = osg::Vec3(layer_span*(i-1)/2, layer_span, 
                          alt_diff * (sin((i+1)*mpi) - 2));
       
-      tc = osg::Vec2(base[0] + layer_scale * (i+1)/4,
-                     base[1] + layer_scale);
+      tc = osg::Vec2(layer_scale * (i+1)/4, layer_scale);
       
       color = osg::Vec4(1.0f, 1.0f, 1.0f, (i == 3) ? 0.0f : 0.15f );
       
@@ -947,15 +957,7 @@ bool SGCloudLayer::reposition( const SGVec3f& p, const SGVec3f& up, double lon,
 
         // cout << "base = " << base[0] << "," << base[1] << endl;
 
-        for (int i = 0; i < 4; i++) {
-          (*tl[i])[0] = base + osg::Vec2(i, 0)*layer_scale/4;
-          for (int j = 0; j < 4; j++) {
-            (*tl[i])[j*2+1] = base + osg::Vec2(i+1, j)*layer_scale/4;
-            (*tl[i])[j*2+2] = base + osg::Vec2(i, j+1)*layer_scale/4;
-          }
-          (*tl[i])[9] = base + osg::Vec2(i+1, 4)*layer_scale/4;
-        }
-
+        setTextureOffset(base);
         last_lon = lon;
         last_lat = lat;
     }
diff --git a/simgear/scene/sky/cloud.hxx b/simgear/scene/sky/cloud.hxx
index 9e38687c..81c9e038 100644
--- a/simgear/scene/sky/cloud.hxx
+++ b/simgear/scene/sky/cloud.hxx
@@ -189,7 +189,8 @@ public:
 
     /** return the 3D layer cloud associated with this 2D layer */
     SGCloudField *get_layer3D(void) { return layer3D; }
-
+protected:
+    void setTextureOffset(const osg::Vec2& offset);
 private:
 
     osg::ref_ptr<osg::Switch> layer_root;
-- 
2.39.5