Added support for using pixel size control of LOD levels.

examples/osgsimulation/osgsimulation.cpp

@@ -5,9 +5,12 @@
 #include <osg/ShapeDrawable>
 #include <osg/Texture2D>
 #include <osg/PositionAttitudeTransform>
+#include <osg/MatrixTransform>
 
 #include <osgDB/ReadFile>
 
+#include <osgText/Text>
+
 #include <osgSim/SphereSegment>
 
 #include <osgParticle/ExplosionEffect>
@@ -18,6 +21,108 @@
 // for the grid data..
 #include "../osghangglide/terrain_coords.h"
 
+osg::AnimationPath* createAnimationPath(const osg::Vec3& center,float radius,double looptime)
+{
+    // set up the animation path 
+    osg::AnimationPath* animationPath = new osg::AnimationPath;
+    animationPath->setLoopMode(osg::AnimationPath::LOOP);
+    
+    int numSamples = 40;
+    float yaw = 0.0f;
+    float yaw_delta = 2.0f*osg::PI/((float)numSamples-1.0f);
+    float roll = osg::inDegrees(30.0f);
+    
+    double time=0.0f;
+    double time_delta = looptime/(double)numSamples;
+    for(int i=0;i<numSamples;++i)
+    {
+        osg::Vec3 position(center+osg::Vec3(sinf(yaw)*radius,cosf(yaw)*radius,0.0f));
+        osg::Quat rotation(osg::Quat(roll,osg::Vec3(0.0,1.0,0.0))*osg::Quat(-(yaw+osg::inDegrees(90.0f)),osg::Vec3(0.0,0.0,1.0)));
+        
+        animationPath->insert(time,osg::AnimationPath::ControlPoint(position,rotation));
+
+        yaw += yaw_delta;
+        time += time_delta;
+
+    }
+    return animationPath;    
+}
+
+osg::Node* createMovingModel(const osg::Vec3& center, float radius)
+{
+    float animationLength = 10.0f;
+
+    osg::AnimationPath* animationPath = createAnimationPath(center,radius,animationLength);
+
+    osg::Group* model = new osg::Group;
+
+    osg::Node* glider = osgDB::readNodeFile("glider.osg");
+    if (glider)
+    {
+        const osg::BoundingSphere& bs = glider->getBound();
+
+        float size = radius/bs.radius()*0.3f;
+        osg::MatrixTransform* positioned = new osg::MatrixTransform;
+        positioned->setDataVariance(osg::Object::STATIC);
+        positioned->setMatrix(osg::Matrix::translate(-bs.center())*
+                                     osg::Matrix::scale(size,size,size)*
+                                     osg::Matrix::rotate(osg::inDegrees(-90.0f),0.0f,0.0f,1.0f));
+    
+        positioned->addChild(glider);
+    
+        osg::PositionAttitudeTransform* xform = new osg::PositionAttitudeTransform;    
+        xform->getOrCreateStateSet()->setMode(GL_NORMALIZE, osg::StateAttribute::ON);
+        xform->setUpdateCallback(new osg::AnimationPathCallback(animationPath,0.0,1.0));
+        xform->addChild(positioned);
+
+        model->addChild(xform);
+    }
+ 
+    osg::Node* cessna = osgDB::readNodeFile("cessna.osg");
+    if (cessna)
+    {
+        const osg::BoundingSphere& bs = cessna->getBound();
+
+        osgText::Text* text = new osgText::Text;
+        float size = radius/bs.radius()*0.3f;
+
+        text->setPosition(bs.center());
+        text->setText("Cessna");
+        text->setAlignment(osgText::Text::CENTER_CENTER);
+        text->setAxisAlignment(osgText::Text::SCREEN);
+        text->setCharacterSize(40.0f);
+        text->setCharacterSizeMode(osgText::Text::SCREEN_COORDS);
+        
+        osg::Geode* geode = new osg::Geode;
+        geode->addDrawable(text);
+    
+        osg::LOD* lod = new osg::LOD;
+        lod->setRangeMode(osg::LOD::PIXEL_SIZE_ON_SCREEN);
+        lod->addChild(geode,0.0f,100.0f);
+        lod->addChild(cessna,100.0f,10000.0f);
+
+
+        osg::MatrixTransform* positioned = new osg::MatrixTransform;
+        positioned->getOrCreateStateSet()->setMode(GL_NORMALIZE, osg::StateAttribute::ON);
+        positioned->setDataVariance(osg::Object::STATIC);
+        positioned->setMatrix(osg::Matrix::translate(-bs.center())*
+                                     osg::Matrix::scale(size,size,size)*
+                                     osg::Matrix::rotate(osg::inDegrees(180.0f),0.0f,0.0f,1.0f));
+    
+        //positioned->addChild(cessna);
+        positioned->addChild(lod);
+    
+        osg::MatrixTransform* xform = new osg::MatrixTransform;
+        xform->setUpdateCallback(new osg::AnimationPathCallback(animationPath,0.0f,2.0));
+        xform->addChild(positioned);
+
+        model->addChild(xform);
+    }
+    
+    return model;
+}
+
+
 osg::Vec3 computeTerrainIntersection(osg::Node* subgraph,float x,float y)
 {
     osgUtil::IntersectVisitor iv;
@@ -132,6 +237,12 @@ void build_world(osg::Group *root)
         // add the updater node to the scene graph
         root->addChild(psu);
     }
+    
+    
+    // create the moving models.
+    {
+        root->addChild(createMovingModel(osg::Vec3(500.0f,500.0f,500.0f),100.0f));
+    }
 }
 
 

include/osg/LOD

@@ -55,14 +55,17 @@ class SG_EXPORT LOD : public Group
         typedef std::pair<float,float>  MinMaxPair;
         typedef std::vector<MinMaxPair> RangeList;
       
+        /** Modes which control how the center of object should be determined when computed which child is active.*/
         enum CenterMode
         {
             USE_BOUNDING_SPHERE_CENTER,
             USER_DEFINED_CENTER
         };
 
+        /** Set how the center of object should be determined when computed which child is active.*/
         void setCenterMode(CenterMode mode) { _centerMode=mode; }
 
+        /** Get how the center of object should be determined when computed which child is active.*/
         CenterMode getCenterMode() const { return _centerMode; }
 
         /** Sets the object-space point which defines the center of the osg::LOD.  
@@ -72,6 +75,21 @@ class SG_EXPORT LOD : public Group
         /** return the LOD center point. */
         inline const Vec3& getCenter() const { if (_centerMode==USER_DEFINED_CENTER) return _userDefinedCenter; else return getBound().center(); }
 
+
+        /** Modes that control how the range values should be intepreted when computing which child is active.*/
+        enum RangeMode
+        {
+            DISTANCE_FROM_EYE_POINT,
+            PIXEL_SIZE_ON_SCREEN
+        };
+        
+        /** Set how the range values should be intepreted when computing which child is active.*/
+        void setRangeMode(RangeMode mode) { _rangeMode = mode; }
+
+        /** Get how the range values should be intepreted when computing which child is active.*/
+        RangeMode getRangeMode() const { return _rangeMode; }
+
+
         /** Sets the min and max visible ranges of range of specifiec child.
             Values are floating point distance specified in local objects coordinates.*/
         void setRange(unsigned int childNo, float min,float max);
@@ -101,6 +119,7 @@ class SG_EXPORT LOD : public Group
         CenterMode                      _centerMode;
         Vec3                            _userDefinedCenter;
 
+        RangeMode                       _rangeMode;
         RangeList                       _rangeList;
 
 };

src/osg/LOD.cpp

@@ -11,6 +11,7 @@
  * OpenSceneGraph Public License for more details.
 */
 #include <osg/LOD>
+#include <osg/CullStack>
 
 #include <algorithm>
 
@@ -39,13 +40,35 @@ void LOD::traverse(NodeVisitor& nv)
             break;
         case(NodeVisitor::TRAVERSE_ACTIVE_CHILDREN):
         {
-            float distance = nv.getDistanceToEyePoint(getCenter(),true);
+            float required_range = 0;
+            if (_rangeMode==DISTANCE_FROM_EYE_POINT)
+            {
+                required_range = nv.getDistanceToEyePoint(getCenter(),true);
+            }
+            else
+            {
+                osg::CullStack* cullStack = dynamic_cast<osg::CullStack*>(&nv);
+                if (cullStack)
+                {
+                    required_range = cullStack->pixelSize(getBound());
+                }
+                else
+                {
+                    // fallback to selecting the highest res tile by
+                    // finding out the max range
+                    for(unsigned int i=0;i<_rangeList.size();++i)
+                    {
+                        required_range = osg::minimum(required_range,_rangeList[i].first);
+                    }
+                }
+            }
+            
             unsigned int numChildren = _children.size();
             if (_rangeList.size()<numChildren) numChildren=_rangeList.size();
 
             for(unsigned int i=0;i<numChildren;++i)
             {    
-                if (_rangeList[i].first<=distance && distance<_rangeList[i].second)
+                if (_rangeList[i].first<=required_range && required_range<_rangeList[i].second)
                 {
                     _children[i]->accept(nv);
                 }