Frustum.cpp

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/* Copyright (C) 2009 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. 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
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * CFrustum is a collection of planes which define a viewing space.
 */

/*
Usually associated with the camera, there are 6 planes which define the
view pyramid. But we allow more planes per frustum which may be used for
portal rendering, where a portal may have 3 or more edges.
*/

#include "precompiled.h"

#include "Frustum.h"
#include "maths/BoundingBoxAligned.h"
#include "maths/MathUtil.h"

CFrustum::CFrustum ()
{
    m_NumPlanes = 0;
}

CFrustum::~CFrustum ()
{
}

void CFrustum::SetNumPlanes (size_t num)
{
    m_NumPlanes = num;

    //clip it
    if (m_NumPlanes >= MAX_NUM_FRUSTUM_PLANES)
        m_NumPlanes = MAX_NUM_FRUSTUM_PLANES-1;
}

void CFrustum::AddPlane (const CPlane& plane)
{
    if (m_NumPlanes >= MAX_NUM_FRUSTUM_PLANES)
    {
        debug_warn(L"CFrustum::AddPlane: Too many planes");
        return;
    }

    m_aPlanes[m_NumPlanes++] = plane;
}

bool CFrustum::IsPointVisible (const CVector3D &point) const
{
    PLANESIDE Side;

    for (size_t i=0; i<m_NumPlanes; i++)
    {
        Side = m_aPlanes[i].ClassifyPoint (point);

        if (Side == PS_BACK)
            return false;
    }

    return true;
}
bool CFrustum::DoesSegmentIntersect(const CVector3D& startRef, const CVector3D &endRef)
{
    CVector3D start = startRef;
    CVector3D end = endRef;

    if(IsPointVisible(start) || IsPointVisible(end))
        return true;

    CVector3D intersect;
    for ( size_t i = 0; i<m_NumPlanes; ++i )
    {
        if ( m_aPlanes[i].FindLineSegIntersection(start, end, &intersect) )
        {
            if ( IsPointVisible( intersect ) )
                return true;
        }
    }
    return false;
}
bool CFrustum::IsSphereVisible (const CVector3D &center, float radius) const
{
    for (size_t i=0; i<m_NumPlanes; i++)
    {
        float Dist = m_aPlanes[i].DistanceToPlane (center);
        
        //is it behind the plane
        if (Dist < 0)
        {
            //if non of it falls in front its outside the
            //frustum
            if (-Dist > radius)
                return false;
        }
    }

    return true;
}


bool CFrustum::IsBoxVisible (const CVector3D &position,const CBoundingBoxAligned &bounds) const
{
    //basically for every plane we calculate the furthest point
    //in the box to that plane. If that point is beyond the plane
    //then the box is not visible
    CVector3D FarPoint;
    PLANESIDE Side;
    CVector3D Min = position+bounds[0];
    CVector3D Max = position+bounds[1];

    for (size_t i=0; i<m_NumPlanes; i++)
    {
        if (m_aPlanes[i].m_Norm.X > 0.0f)
        {
            if (m_aPlanes[i].m_Norm.Y > 0.0f)
            {
                if (m_aPlanes[i].m_Norm.Z > 0.0f)
                {
                    FarPoint.X = Max.X; FarPoint.Y = Max.Y; FarPoint.Z = Max.Z;
                }
                else
                {
                    FarPoint.X = Max.X; FarPoint.Y = Max.Y; FarPoint.Z = Min.Z;
                }
            }
            else
            {
                if (m_aPlanes[i].m_Norm.Z > 0.0f)
                {
                    FarPoint.X = Max.X; FarPoint.Y = Min.Y; FarPoint.Z = Max.Z;
                }
                else
                {
                    FarPoint.X = Max.X; FarPoint.Y = Min.Y; FarPoint.Z = Min.Z;
                }
            }
        }
        else
        {
            if (m_aPlanes[i].m_Norm.Y > 0.0f)
            {
                if (m_aPlanes[i].m_Norm.Z > 0.0f)
                {
                    FarPoint.X = Min.X; FarPoint.Y = Max.Y; FarPoint.Z = Max.Z;
                }
                else
                {
                    FarPoint.X = Min.X; FarPoint.Y = Max.Y; FarPoint.Z = Min.Z;
                }
            }
            else
            {
                if (m_aPlanes[i].m_Norm.Z > 0.0f)
                {
                    FarPoint.X = Min.X; FarPoint.Y = Min.Y; FarPoint.Z = Max.Z;
                }
                else
                {
                    FarPoint.X = Min.X; FarPoint.Y = Min.Y; FarPoint.Z = Min.Z;
                }
            }
        }
        
        Side = m_aPlanes[i].ClassifyPoint (FarPoint);

        if (Side == PS_BACK)
            return false;
    }

    return true;
}