mgcterrainblock.cpp

《3D游戏引擎设计》的源码

// Magic Software, Inc.
// http://www.magic-software.com
// Copyright (c) 2000, All Rights Reserved
//
// Source code from Magic Software is supplied under the terms of a license
// agreement and may not be copied or disclosed except in accordance with the
// terms of that agreement.  The various license agreements may be found at
// the Magic Software web site.  This file is subject to the license
//
// RESTRICTED USE SOURCE CODE
// http://www.magic-software.com/License/restricted.pdf

#include "MgcBox3.h"
#include "MgcCamera.h"
#include "MgcFrustum.h"
#include "MgcTerrainBlock.h"
#include "MgcTerrainPage.h"
#include "MgcTerrainVertex.h"

//---------------------------------------------------------------------------
void MgcTerrainBlock::GetVertex9 (unsigned short usSize,
    MgcTerrainVertex* pkVOrigin, MgcTerrainVertex* apkTVertex[9])
{
    unsigned short usOrigin = m_ucX+usSize*m_ucY;
    unsigned short usTwoStride = 2*m_ucStride;
    unsigned short usSizePlus1 = usSize+1;
    unsigned short usSizePlus2 = usSize+2;
    unsigned short usTwoSizePlus1 = 2*usSize+1;
    unsigned short usSizeTimesStride = usSize*m_ucStride;
    unsigned short usSizePlus1TimesStride = usSizePlus1*m_ucStride;
    unsigned short usSizePlus2TimesStride = usSizePlus2*m_ucStride;
    unsigned short usSizeTimesTwoStride = usSize*usTwoStride;
    unsigned short usTwoSizePlus1TimesStride = usTwoSizePlus1*m_ucStride;
    unsigned short usSizePlus1TimesTwoStride = usSizePlus1*usTwoStride;

    pkVOrigin += usOrigin;
    apkTVertex[0] = &pkVOrigin[0];
    apkTVertex[1] = &pkVOrigin[m_ucStride];
    apkTVertex[2] = &pkVOrigin[usTwoStride];
    apkTVertex[3] = &pkVOrigin[usSizeTimesStride];
    apkTVertex[4] = &pkVOrigin[usSizePlus1TimesStride];
    apkTVertex[5] = &pkVOrigin[usSizePlus2TimesStride];
    apkTVertex[6] = &pkVOrigin[usSizeTimesTwoStride];
    apkTVertex[7] = &pkVOrigin[usTwoSizePlus1TimesStride];
    apkTVertex[8] = &pkVOrigin[usSizePlus1TimesTwoStride];
}
//---------------------------------------------------------------------------
void MgcTerrainBlock::Initialize (MgcTerrainPage* pkPage,
    MgcTerrainBlock* pkBlock, unsigned short usBlock, unsigned char ucX,
    unsigned char ucY, unsigned char ucStride, bool bEven)
{
    m_ucX = ucX;
    m_ucY = ucY;
    m_ucStride = ucStride;
    m_ucFlags = 0;
    m_fDeltaL = 0.0;
    m_fDeltaH = MgcMath::INFINITY;
    SetEven(bEven);

    MgcTerrainVertex* akTVertex[9];
    GetVertex9(pkPage->m_usSize,pkPage->m_akTVertex,akTVertex);

    // set vertex dependencies
    akTVertex[1]->SetDependent(0,akTVertex[4]);
    akTVertex[3]->SetDependent(1,akTVertex[4]);
    akTVertex[5]->SetDependent(0,akTVertex[4]);
    akTVertex[7]->SetDependent(1,akTVertex[4]);
    if ( bEven )
    {
        akTVertex[4]->SetDependent(0,akTVertex[6]);
        akTVertex[4]->SetDependent(1,akTVertex[2]);
    }
    else
    {
        akTVertex[4]->SetDependent(0,akTVertex[0]);
        akTVertex[4]->SetDependent(1,akTVertex[8]);
    }

    // recurse on children (if any)
    if ( ucStride > 1 )
    {
        // child stride is half the parent stride
        unsigned char ucChildStride = ( ucStride >> 1 );

        // process child 00
        unsigned short usChild = GetChildIndex(usBlock,1);
        MgcTerrainBlock* pkChild = &pkBlock[usChild];
        pkChild->Initialize(pkPage,pkBlock,usChild,ucX,ucY,ucChildStride,
            true);

        // process child 01
        usChild++;
        pkChild++;
        pkChild->Initialize(pkPage,pkBlock,usChild,ucX+ucStride,ucY,
            ucChildStride,false);

        // process child 10
        usChild++;
        pkChild++;
        pkChild->Initialize(pkPage,pkBlock,usChild,ucX,ucY+ucStride,
            ucChildStride,false);

        // process child 11
        usChild++;
        pkChild++;
        pkChild->Initialize(pkPage,pkBlock,usChild,ucX+ucStride,ucY+ucStride,
            ucChildStride,true);
    }
}
//---------------------------------------------------------------------------
void MgcTerrainBlock::UpdateBoundingBox (MgcTerrainPage* pkPage,
    MgcTerrainBlock* pkBlock, unsigned short usBlock, unsigned char ucStride)
{
    MgcVector3 akPoint[9];
    akPoint[0].x = pkPage->GetX(m_ucX);
    akPoint[0].y = pkPage->GetY(m_ucY);
    akPoint[1].x = pkPage->GetX(m_ucX + m_ucStride);
    akPoint[1].y = akPoint[0].y;
    akPoint[2].x = pkPage->GetX(m_ucX + 2*m_ucStride);
    akPoint[2].y = akPoint[0].y;
    akPoint[3].x = akPoint[0].x;
    akPoint[3].y = pkPage->GetY(m_ucY + m_ucStride);
    akPoint[4].x = akPoint[1].x;
    akPoint[4].y = akPoint[3].y;
    akPoint[5].x = akPoint[2].x;
    akPoint[5].y = akPoint[3].y;
    akPoint[6].x = akPoint[0].x;
    akPoint[6].y = pkPage->GetY(m_ucY + 2*m_ucStride);
    akPoint[7].x = akPoint[1].x;
    akPoint[7].y = akPoint[6].y;
    akPoint[8].x = akPoint[2].x;
    akPoint[8].y = akPoint[6].y;

    unsigned short usOrigin = m_ucX + pkPage->m_usSize*m_ucY;
    akPoint[0].z = pkPage->GetHeight(usOrigin);
    akPoint[1].z = pkPage->GetHeight(usOrigin+ucStride);
    akPoint[2].z = pkPage->GetHeight(usOrigin+2*ucStride);
    usOrigin += pkPage->m_usSize*ucStride;
    akPoint[3].z = pkPage->GetHeight(usOrigin);
    akPoint[4].z = pkPage->GetHeight(usOrigin+ucStride);
    akPoint[5].z = pkPage->GetHeight(usOrigin+2*ucStride);
    usOrigin += pkPage->m_usSize*ucStride;
    akPoint[6].z = pkPage->GetHeight(usOrigin);
    akPoint[7].z = pkPage->GetHeight(usOrigin+ucStride);
    akPoint[8].z = pkPage->GetHeight(usOrigin+2*ucStride);

    // compute (x,y) components of bounding box
    m_kMin.x = akPoint[0].x;
    m_kMin.y = akPoint[0].y;
    m_kMax.x = akPoint[8].x;
    m_kMax.y = akPoint[8].y;
    
    // compute delta max
    MgcReal fC0 = akPoint[0].z;
    MgcReal fMd = akPoint[1].z;
    MgcReal fC1 = akPoint[2].z;
    m_fDelta[0] = 0.5*(fC0+fC1)-fMd;
    m_fDelta[0] *= m_fDelta[0];
    
    fC0 = akPoint[8].z;
    fMd = akPoint[5].z;
    m_fDelta[1] = 0.5*(fC0+fC1)-fMd;
    m_fDelta[1] *= m_fDelta[1];
    
    fMd = akPoint[7].z;
    fC1 = akPoint[6].z;
    m_fDelta[2] = 0.5*(fC0+fC1)-fMd;
    m_fDelta[2] *= m_fDelta[2];
    
    fC0 = akPoint[0].z;
    fMd = akPoint[3].z;
    m_fDelta[3] = 0.5*(fC0+fC1)-fMd;
    m_fDelta[3] *= m_fDelta[3];
    
    fMd = akPoint[4].z;
    if ( GetEven() )
    {
        fC0 = akPoint[2].z;
        fC1 = akPoint[6].z;
    }
    else
    {
        fC0 = akPoint[0].z;
        fC1 = akPoint[8].z;
    }
    m_fDelta[4] = 0.5*(fC0+fC1)-fMd;
    m_fDelta[4] *= m_fDelta[4];

    m_fDeltaMax = m_fDelta[0];
    for (int i = 1; i < 5; i++)
    {
        if ( m_fDelta[i] > m_fDeltaMax )
            m_fDeltaMax = m_fDelta[i];
    }

    // recurse on children (if any)
    if ( ucStride > 1 )
    {
        // child stride is half the parent stride
        unsigned char ucChildStride = ( ucStride >> 1 );

        // process child 00
        unsigned short usChild = GetChildIndex(usBlock,1);
        MgcTerrainBlock* pkChild = &pkBlock[usChild];
        pkChild->UpdateBoundingBox(pkPage,pkBlock,usChild,ucChildStride);
        if ( pkChild->m_fDeltaMax > m_fDeltaMax )
            m_fDeltaMax = pkChild->m_fDeltaMax;
        m_kMin.z = pkChild->m_kMin.z;
        m_kMax.z = pkChild->m_kMax.z;

        // process child 01
        usChild++;
        pkChild++;
        pkChild->UpdateBoundingBox(pkPage,pkBlock,usChild,ucChildStride);
        if ( pkChild->m_fDeltaMax > m_fDeltaMax )
            m_fDeltaMax = pkChild->m_fDeltaMax;
        if ( pkChild->m_kMin.z < m_kMin.z )
            m_kMin.z = pkChild->m_kMin.z;
        if ( pkChild->m_kMax.z > m_kMax.z )
            m_kMax.z = pkChild->m_kMax.z;

        // process child 10
        usChild++;
        pkChild++;
        pkChild->UpdateBoundingBox(pkPage,pkBlock,usChild,ucChildStride);
        if ( pkChild->m_fDeltaMax > m_fDeltaMax )
            m_fDeltaMax = pkChild->m_fDeltaMax;
        if ( pkChild->m_kMin.z < m_kMin.z )
            m_kMin.z = pkChild->m_kMin.z;
        if ( pkChild->m_kMax.z > m_kMax.z )
            m_kMax.z = pkChild->m_kMax.z;

        // process child 11
        usChild++;
        pkChild++;
        pkChild->UpdateBoundingBox(pkPage,pkBlock,usChild,ucChildStride);
        if ( pkChild->m_fDeltaMax > m_fDeltaMax )
            m_fDeltaMax = pkChild->m_fDeltaMax;
        if ( pkChild->m_kMin.z < m_kMin.z )
            m_kMin.z = pkChild->m_kMin.z;
        if ( pkChild->m_kMax.z > m_kMax.z )
            m_kMax.z = pkChild->m_kMax.z;
    }
    else
    {
        // compute z components of bounding box at leaf node of quadtree
        m_kMin.z = akPoint[0].z;
        m_kMax.z = m_kMin.z;
        for (unsigned short usIndex = 1; usIndex < 9; usIndex++)
        {
            MgcReal fZ = akPoint[usIndex].z;
            if ( fZ < m_kMin.z )
                m_kMin.z = fZ;
            if ( fZ > m_kMax.z )
                m_kMax.z = fZ;
        }
    }
}
//---------------------------------------------------------------------------
void MgcTerrainBlock::ComputeInterval (const MgcVector3& rkModelEye,
    MgcReal fTolerance)
{
    // distant terrain assumption

    if ( fTolerance > 0.0 )
    {
        // compute hmin = |eye.z - clamp(bmin.z,eye.z,bmax.z)|
        MgcReal fHMin;
        if ( rkModelEye.z < m_kMin.z )
        {
            fHMin = rkModelEye.z - m_kMin.z;
            fHMin *= fHMin;
        }
        else if ( rkModelEye.z > m_kMax.z )
        {
            fHMin = rkModelEye.z - m_kMax.z;
            fHMin *= fHMin;
        }
        else
        {
            fHMin = 0.0;
        }

        // compute hmax = max{|eye.z - bmin.z|,|eye.z - bmax.z|}
        MgcReal fHMax = rkModelEye.z - m_kMin.z;
        fHMax *= fHMax;
        MgcReal fTmp = rkModelEye.z - m_kMax.z;
        fTmp *= fTmp;
        if ( fTmp > fHMax )
            fHMax = fTmp;

        // compute rmin and rmax
        MgcReal fDxMin = rkModelEye.x - m_kMin.x;
        MgcReal fDxMax = rkModelEye.x - m_kMax.x;
        MgcReal fDyMin = rkModelEye.y - m_kMin.y;
        MgcReal fDyMax = rkModelEye.y - m_kMax.y;
        fDxMin *= fDxMin;
        fDxMax *= fDxMax;
        fDyMin *= fDyMin;
        fDyMax *= fDyMax;
        MgcReal fRMin = 0.0, fRMax = 0.0;

        if ( rkModelEye.x < m_kMin.x )
        {
            fRMin += fDxMin;
            fRMax += fDxMax;
        }
        else if ( rkModelEye.x <= m_kMax.x )
        {