OccluderGeometry

/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSGSHADOW_OCCLUDERGEOMETRY
#define OSGSHADOW_OCCLUDERGEOMETRY 1

#include <osg/Drawable>
#include <osg/Array>
#include <osg/PrimitiveSet>
#include <osg/Polytope>

#include <osgShadow/Export>


namespace osgShadow {

class ShadowVolumeGeometry;

/** OccluderGeometry provides a sepecialised geometry representation of objects in scene that occlude light and therefore cast shadows.
  * OccluderGeometry supports the computation of silhouette edges and shadow volume geometries, as well as use as geometry that one can rendering
  * into a shadow map or end caps for the ZP+ algorithm.  OccluderGeometry may be of the same resolution as an underlying geometry that it
  * represents, or can be of lower resolution and combine manager seperate geometries together into a single shadow casting object. 
  * OccluderGeometry may be attached as UserData to Nodes or to Drawables.  */
class OSGSHADOW_EXPORT OccluderGeometry : public osg::Drawable
{
    public :
        OccluderGeometry();

        OccluderGeometry(const OccluderGeometry& oc, const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY);
            
        virtual Object* cloneType() const { return new OccluderGeometry(); }
        virtual Object* clone(const osg::CopyOp& copyop) const { return new OccluderGeometry(*this,copyop); }
        virtual bool isSameKindAs(const osg::Object* obj) const { return dynamic_cast<const OccluderGeometry*>(obj)!=NULL; }
        virtual const char* libraryName() const { return "osgShadow"; }
        virtual const char* className() const { return "OccluderGeometry"; }
        
        /** Compute an occluder geometry containing all the geometry in specified subgraph.*/
        void computeOccluderGeometry(osg::Node* subgraph, osg::Matrix* matrix=0, float sampleRatio=1.0f);
        
        /** Compute an occluder geometry containing the geometry in specified drawable.*/
        void computeOccluderGeometry(osg::Drawable* drawable, osg::Matrix* matrix=0, float sampleRatio=1.0f);
        

        /** Compute ShadowVolumeGeometry. */
        void computeShadowVolumeGeometry(const osg::Vec4& lightpos, ShadowVolumeGeometry& svg) const;

        
        /** Set the bounding polytope of the OccluderGeometry.*/
        void setBoundingPolytope(const osg::Polytope& polytope) { _boundingPolytope = polytope; }

        /** Get the bounding polytope of the OccluderGeometry.*/
        osg::Polytope& getBoundingPolytope() { return _boundingPolytope; }

        /** Get the const bounding polytope of the OccluderGeometry.*/
        const osg::Polytope& getBoundingPolytope() const { return _boundingPolytope; }


        /** Render the occluder geometry. */
        virtual void drawImplementation(osg::RenderInfo& renderInfo) const;
        
        /** Compute the bounding box around occluder geometry.*/
        virtual osg::BoundingBox computeBound() const;

        typedef std::vector<osg::Vec3> Vec3List;
        typedef std::vector<GLuint> UIntList;

    public:

        void processGeometry(osg::Drawable* drawable, osg::Matrix* matrix=0, float sampleRatio=1.0f);

    protected :

        virtual ~OccluderGeometry() {}
        
        struct Edge
        {
            Edge():
                _p1(0),
                _p2(0),
                _t1(-1),
                _t2(-1) {}

            Edge(unsigned int p1, unsigned int p2):
                _p1(p1),
                _p2(p2),
                _t1(-1),
                _t2(-1)
            {
                if (p1>p2)
                {
                    // swap ordering so p1 is less than or equal to p2
                    _p1 = p2;
                    _p2 = p1;
                }
            }
            
            inline bool operator < (const Edge& rhs) const
            {
                if (_p1 < rhs._p1) return true;
                if (_p1 > rhs._p1) return false;
                return (_p2 < rhs._p2);
            }
            
            bool addTriangle(unsigned int tri) const
            {
                if (_t1<0)
                {
                    _t1 = tri;
                    return true;
                }
                else if (_t2<0)
                {
                    _t2 = tri;
                    return true;
                }
                // argg more than two triangles assigned
                return false;
            }
            
            bool boundaryEdge() const { return _t2<0; }
        
            unsigned int    _p1;
            unsigned int    _p2;
            
            mutable int     _t1;
            mutable int     _t2;
            
            mutable osg::Vec3   _normal;
        };

        typedef std::vector<Edge> EdgeList;

        inline bool isLightPointSilhouetteEdge(const osg::Vec3& lightpos, const Edge& edge) const
        {
            if (edge.boundaryEdge()) return true;
            
            float offset = 0.0f;

            osg::Vec3 delta(lightpos-_vertices[edge._p1]);
            delta.normalize();
            
            float n1 = delta * _triangleNormals[edge._t1] + offset;
            float n2 = delta * _triangleNormals[edge._t2] + offset;

            float angle_offset = 0.0f;

            n1 = cos(acosf(n1) + angle_offset);
            n2 = cos(acosf(n2) + angle_offset);

            if (n1==0.0f && n2==0.0f) return false;
            
            return n1*n2 <= 0.0f; 
        }

        inline bool isLightDirectionSilhouetteEdge(const osg::Vec3& lightdirection, const Edge& edge) const
        {
            if (edge.boundaryEdge()) return true;
            
            float offset = 0.0f;
            
            float n1 = lightdirection * _triangleNormals[edge._t1] + offset;
            float n2 = lightdirection * _triangleNormals[edge._t2] + offset;

            float angle_offset = 0.0f;

            n1 = cos(acosf(n1) + angle_offset);
            n2 = cos(acosf(n2) + angle_offset);

            if (n1==0.0f && n2==0.0f) return false;
            
            return n1*n2 <= 0.0f; 
        }
        
        void setUpInternalStructures();
        
        void removeDuplicateVertices();
        void removeNullTriangles();
        void computeNormals();
        void buildEdgeMaps();
        
        void computeLightDirectionSilhouetteEdges(const osg::Vec3& lightdirection, UIntList& silhouetteIndices) const;
        void computeLightPositionSilhouetteEdges(const osg::Vec3& lightpos, UIntList& silhouetteIndices) const;

        osg::Polytope _boundingPolytope;

        Vec3List _vertices;
        Vec3List _normals;
        Vec3List _triangleNormals;
        UIntList _triangleIndices;
        
        EdgeList _edges;
};

class OSGSHADOW_EXPORT ShadowVolumeGeometry : public osg::Drawable
{
    public :
        ShadowVolumeGeometry();

        ShadowVolumeGeometry(const ShadowVolumeGeometry& oc, const osg::CopyOp& copyop=osg::CopyOp::SHALLOW_COPY);
            
        virtual Object* cloneType() const { return new ShadowVolumeGeometry(); }
        virtual Object* clone(const osg::CopyOp& copyop) const { return new ShadowVolumeGeometry(*this,copyop); }
        virtual bool isSameKindAs(const osg::Object* obj) const { return dynamic_cast<const ShadowVolumeGeometry*>(obj)!=NULL; }
        virtual const char* libraryName() const { return "osgShadow"; }
        virtual const char* className() const { return "ShadowVolumeGeometry"; }

        enum DrawMode
        {
            GEOMETRY,
            STENCIL_TWO_PASS,
            STENCIL_TWO_SIDED
        };
        
        void setDrawMode(DrawMode mode) { _drawMode = mode; }
        DrawMode getDrawMode() const { return _drawMode; }

        typedef std::vector<osg::Vec3> Vec3List;
        typedef std::vector<GLuint> UIntList;
        
        void setVertices(const Vec3List& vertices) { _vertices = vertices; }
        Vec3List& getVertices() { return _vertices; }
        const Vec3List& getVertices() const { return _vertices; }
        
        void setNormals(const Vec3List& normals) { _normals = normals; }
        Vec3List& getNormals() { return _normals; }
        const Vec3List& getNormals() const { return _normals; }
        

        /** Render the occluder geometry. */
        virtual void drawImplementation(osg::RenderInfo& renderInfo) const;
        
        /** Compute the bounding box around occluder geometry.*/
        virtual osg::BoundingBox computeBound() const;

    public:

    protected :

        virtual ~ShadowVolumeGeometry() {}

        DrawMode _drawMode;
        Vec3List _vertices;
        Vec3List _normals;
        UIntList _indices;
};

}

#endif