From 5044a85c9ef4b9c1267ea18023db69aa7ec5a1f6 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Fri, 24 Nov 2006 17:20:01 +0000
Subject: [PATCH] Improved handling of bounding polytope

---
 examples/osgshadow/osgshadow.cpp   | 31 +++++++++++----
 include/osg/Plane                  |  8 ++++
 src/osgShadow/OccluderGeometry.cpp | 64 ++++++++++++++++++++++++------
 3 files changed, 82 insertions(+), 21 deletions(-)

diff --git a/examples/osgshadow/osgshadow.cpp b/examples/osgshadow/osgshadow.cpp
index 1f17fbe94..2bd201283 100644
--- a/examples/osgshadow/osgshadow.cpp
+++ b/examples/osgshadow/osgshadow.cpp
@@ -22,6 +22,19 @@ public:
     }
     
     osg::BoundingBox& getBoundingBox() { return _bb; }
+
+    void getPolytope(osg::Polytope& polytope, float margin=0.1) const
+    {
+        float delta = _bb.radius()*margin;
+        polytope.add( osg::Plane(0.0, 0.0, 1.0, -(_bb.zMin()-delta)) );
+        polytope.add( osg::Plane(0.0, 0.0, -1.0, (_bb.zMax()+delta)) );
+
+        polytope.add( osg::Plane(1.0, 0.0, 0.0, -(_bb.xMin()-delta)) );
+        polytope.add( osg::Plane(-1.0, 0.0, 0.0, (_bb.xMax()+delta)) );
+
+        polytope.add( osg::Plane(0.0, 1.0, 0.0, -(_bb.yMin()-delta)) );
+        polytope.add( osg::Plane(0.0, -1.0, 0.0, (_bb.yMax()+delta)) );
+    }
         
     void apply(osg::Node& node)
     {
@@ -137,24 +150,26 @@ int main(int argc, char** argv)
         return 1;
     }
     
-    ComputeBoundingBoxVisitor cbbv;
-    model->accept(cbbv);
-    const osg::BoundingBox& bb = cbbv.getBoundingBox();
-    osg::Plane basePlane(0.0, 0.0, 1.0, -bb.zMin() );
     
     osg::ref_ptr<osg::Geode> geode = new osg::Geode;
 
     osg::ref_ptr<osgShadow::OccluderGeometry> occluder = new osgShadow::OccluderGeometry;
     occluder->computeOccluderGeometry(model.get());
-    occluder->getBoundingPolytope().add(basePlane);
+
+    ComputeBoundingBoxVisitor cbbv;
+    model->accept(cbbv);
+    cbbv.getPolytope(occluder->getBoundingPolytope(),0.001);
+    osg::BoundingBox bb = cbbv.getBoundingBox();
+
     //geode->addDrawable(occluder.get());
     
     osg::ref_ptr<osgShadow::ShadowVolumeGeometry> shadowVolume = new osgShadow::ShadowVolumeGeometry;
 
-#if 0
-    occluder->comptueShadowVolumeGeometry(osg::Vec4(bb.xMin(), bb.yMin(), bb.zMax() + bb.radius() ,1.0f), *shadowVolume);
+#if 1
+//    occluder->comptueShadowVolumeGeometry(osg::Vec4(bb.xMin()+ bb.radius(), bb.yMin()+ bb.radius(), bb.zMax() + bb.radius()  ,1.0f), *shadowVolume);
+    occluder->comptueShadowVolumeGeometry(osg::Vec4(bb.center().x(), bb.center().y(), bb.zMax() + bb.radius()  ,1.0f), *shadowVolume);
 #else
-    occluder->comptueShadowVolumeGeometry(osg::Vec4(0.5f,-.5f,-1.0f,0.0f), *shadowVolume);
+    occluder->comptueShadowVolumeGeometry(osg::Vec4(0.5f,.25f,0.2f,0.0f), *shadowVolume);
 #endif
     geode->addDrawable(shadowVolume.get());
 
diff --git a/include/osg/Plane b/include/osg/Plane
index 51bdb4f36..4acaf2320 100644
--- a/include/osg/Plane
+++ b/include/osg/Plane
@@ -123,6 +123,14 @@ class OSG_EXPORT Plane
                    _fv[3];
         }
 
+        /** calculate the dot product of the plane normal and a point.*/
+        inline float dotProductNormal(const osg::Vec3& v) const
+        {
+            return _fv[0]*v.x()+
+                   _fv[1]*v.y()+
+                   _fv[2]*v.z();
+        }
+
         /** intersection test between plane and vertex list
             return 1 if the bs is completely above plane,
             return 0 if the bs intersects the plane,
diff --git a/src/osgShadow/OccluderGeometry.cpp b/src/osgShadow/OccluderGeometry.cpp
index 437f935cd..a3b4a5cbe 100644
--- a/src/osgShadow/OccluderGeometry.cpp
+++ b/src/osgShadow/OccluderGeometry.cpp
@@ -743,15 +743,15 @@ void OccluderGeometry::comptueShadowVolumeGeometry(const osg::Vec4& lightpos, Sh
     ShadowVolumeGeometry::Vec3List& shadowNormals = svg.getNormals();
     shadowNormals.clear();
 
-    osg::Plane basePlane(0.0, 0.0, 1.0, 0.0);
-    
-    const osg::Polytope::PlaneList& planes = _boundingPolytope.getPlaneList();
-    
-    if (!planes.empty())
+
+    // need to have some kind of handling of case when no planes exist.
+    if (_boundingPolytope.getPlaneList().empty())
     {
-        basePlane = planes[0];
+        osg::notify(osg::NOTICE)<<"Warning: no bounding polytope registered with OccluderGeometry."<<std::endl;
+        return;
     }
 
+
     if (lightpos.w()==0.0)
     {
         // directional light.
@@ -759,13 +759,29 @@ void OccluderGeometry::comptueShadowVolumeGeometry(const osg::Vec4& lightpos, Sh
         
         osg::notify(osg::NOTICE)<<"Directional light"<<std::endl;
         
+        // choose the base plane
+        const osg::Polytope::PlaneList& planes = _boundingPolytope.getPlaneList();
+        osg::Polytope::PlaneList::const_iterator pitr = planes.begin();
+        osg::Plane basePlane = *pitr;
+        ++pitr;
+
+        for(;
+            pitr != planes.end();
+            ++pitr)
+        {
+            if (basePlane.dotProductNormal(lightdirection)  > pitr->dotProductNormal(lightdirection))
+            {
+                basePlane = *pitr;
+            }
+        }
+
         // compute the silhouette edge
         UIntList silhouetteIndices;
         computeLightDirectionSlihouetteEdges(lightdirection, silhouetteIndices);
         
         osg::Vec3 offset( lightdirection*5.0f );
         
-        float directionScale = 1.0f / (basePlane.getNormal() * lightdirection);
+        float directionScale = 1.0f / basePlane.dotProductNormal(lightdirection);
         
         for(UIntList::iterator itr = silhouetteIndices.begin();
             itr != silhouetteIndices.end();
@@ -799,10 +815,16 @@ void OccluderGeometry::comptueShadowVolumeGeometry(const osg::Vec4& lightpos, Sh
         // positional light
         osg::Vec3 lightposition( lightpos.x(), lightpos.y(), lightpos.z());
 
+        osg::Plane basePlane(0.0, 0.0, 1.0, 0.0);
+
         osg::notify(osg::NOTICE)<<"Positional light"<<std::endl;
         UIntList silhouetteIndices;
         computeLightPositionSlihouetteEdges(lightposition, silhouetteIndices);
         
+        osg::notify(osg::NOTICE)<<"basePlane "<<basePlane[0]<<" "<<basePlane[1]<<" "<<basePlane[2]<<" "<<basePlane[3]<<std::endl;
+        osg::notify(osg::NOTICE)<<"lightpos  = "<<std::endl;
+        const osg::Polytope::PlaneList& planes = _boundingPolytope.getPlaneList();
+
         for(UIntList::iterator itr = silhouetteIndices.begin();
             itr != silhouetteIndices.end();
             )
@@ -810,14 +832,30 @@ void OccluderGeometry::comptueShadowVolumeGeometry(const osg::Vec4& lightpos, Sh
             const osg::Vec3& v1 = _vertices[*itr++];
             const osg::Vec3& v2 = _vertices[*itr++];
             
-            osg::Vec3d d1 = v1 - lightposition;
-            osg::Vec3d d2 = v2 - lightposition;
+            osg::Vec3 d1 = v1 - lightposition;
+            osg::Vec3 d2 = v2 - lightposition;
 
-            float r1 = basePlane.distance(v1) / (basePlane.getNormal() * d1);
-            float r2 = basePlane.distance(v2) / (basePlane.getNormal() * d2);
+            osg::Polytope::PlaneList::const_iterator pitr = planes.begin();
+            float r1 = - pitr->distance(v1) / (pitr->dotProductNormal(d1));
+            float r2 = - pitr->distance(v2) / (pitr->dotProductNormal(d2));
+            ++pitr;
 
-            osg::Vec3 v1_projected = v1 - (d1 * r1);
-            osg::Vec3 v2_projected = v2 - (d2 * r2);
+            for(;
+                pitr != planes.end();
+                ++pitr)
+            {
+                float lr1 = - pitr->distance(v1) / (pitr->dotProductNormal(d1));
+                float lr2 = - pitr->distance(v2) / (pitr->dotProductNormal(d2));
+
+                if (lr1>=0.0f && lr2>=0.0f && (lr1+lr2)<(r1+r2))
+                {
+                    r1 = lr1;
+                    r2 = lr2;
+                }
+            }
+
+            osg::Vec3 v1_projected = v1 + (d1 * r1);
+            osg::Vec3 v2_projected = v2 + (d2 * r2);
 
             shadowVertices.push_back( v1);
             shadowVertices.push_back( v1_projected);