source: GTP/trunk/Lib/Geom/shared/GTGeometry/src/GeoLodManager.cpp @ 1071

/*==========================================================================
 *      (C) 2006 Universitat Jaume I
 *==========================================================================
 *      PROYECT:        GAME TOOLS
 *==========================================================================
 *      CONTENT:
 *
 *
 *      @file   GeoLodManager.cpp
 *===========================================================================*/

#include "GeoLodManager.h"
#include "GeoLodObject.h"

namespace Geometry
{
        class lodobj_idpos_node_t
        {
        public:
                lodobj_idpos_node_t(LodObject *o):lodobj(o),must_recalculate_distance(true),dist2cam(0.0f){}
                LodObject *lodobj;
                float dist2cam; // used to index the lodobj in the other map
                bool must_recalculate_distance;
                bool operator < (const lodobj_idpos_node_t &o) const { return (lodobj->GetUniqueID()<o.lodobj->GetUniqueID()); }
        };
}

using namespace Geometry;

LodManager::LodManager(float near, float far, const Geometry::Vector3 &campos)
:targetFPS(30),camera_changed(true),camera_pos(campos),
 near_range(near),far_range(far)
{
}

void Geometry::LodManager::AddLodObj(LodObject * o, const Geometry::Vector3 &p)
{
        float dist = CalculateDistToCamera(p);  
        lodobj_dists[dist] = lodobj_dist_node_t(o);
        UpdateLODObjectPos(o,p);
}


void Geometry::LodManager::UpdateLOD(void)
{
        // recalculate distances if have to
        if (camera_changed)
        {
                // if the camera has changed, recalculate all lodobject distances to it         
                lodobj_dists.clear();
                for (std::map<Geometry::lodobj_idpos_node_t,Geometry::Vector3>::iterator it = lodobj_pos.begin(); it != lodobj_pos.end(); it++)
                {
                        const lodobj_idpos_node_t & posnode = it->first;
                        const Vector3 & pos = it->second;
                        float newdist = CalculateDistToCamera(pos);
                        lodobj_dists[newdist] = lodobj_dist_node_t(posnode.lodobj);
                }
                camera_changed=false;
        }
        else
        {
                // if any of the objects changed its position, the distance must be recalculated
                for (std::map<Geometry::lodobj_idpos_node_t,Geometry::Vector3>::iterator it = lodobj_pos.begin(); it != lodobj_pos.end(); it++)
                {
                        const lodobj_idpos_node_t & posnode = it->first;
                        if (posnode.must_recalculate_distance)
                        {
                                const Vector3 & pos = it->second;
                                float newdist = CalculateDistToCamera(pos);
                                lodobj_dists[newdist] = lodobj_dist_node_t(posnode.lodobj);
/*                              lodobj_dists.erase(it);*/
                        }
                }
        }

        // select a tree to change its LOD
        float random_dist = SelectRandomDistance();
        std::map<float,Geometry::lodobj_dist_node_t>::iterator nearest = lodobj_dists.upper_bound(random_dist);
}

void Geometry::LodManager::UpdateCamera(const Geometry::Vector3 &p)
{
        camera_pos = p;
        camera_changed = true;
}

void Geometry::LodManager::UpdateLODObjectPos(LodObject *o, const Geometry::Vector3 &p)
{
        lodobj_pos[lodobj_idpos_node_t(o)] = p;
}


float Geometry::LodManager::CalculateDistToCamera(const Geometry::Vector3 &p) const
{
        return camera_pos.dotProduct(p);
}

float Geometry::LodManager::SelectRandomDistance(void) const
{
        float linear_01 = (float)rand()/(float)RAND_MAX;
        float exp_01 = linear_01*linear_01;
        float real_dist = exp_01*near_range + (1.0f-exp_01)*far_range;
        return real_dist;
}