source: ps/trunk/source/graphics/Terrain.cpp@ 9929

/* Copyright (C) 2011 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/>.
 */

/*
 * Describes ground via heightmap and array of CPatch.
 */

#include "precompiled.h"

#include "lib/res/graphics/ogl_tex.h"
#include "lib/sysdep/cpu.h"

#include "renderer/Renderer.h"

#include "TerrainProperties.h"
#include "TerrainTextureEntry.h"
#include "TerrainTextureManager.h"

#include <string.h>
#include "Terrain.h"
#include "Patch.h"
#include "maths/FixedVector3D.h"
#include "maths/MathUtil.h"
#include "ps/CLogger.h"

///////////////////////////////////////////////////////////////////////////////
// CTerrain constructor
CTerrain::CTerrain()
: m_Heightmap(0), m_Patches(0), m_MapSize(0), m_MapSizePatches(0),
m_BaseColour(255, 255, 255, 255)
{
}

///////////////////////////////////////////////////////////////////////////////
// CTerrain constructor
CTerrain::~CTerrain()
{
    ReleaseData();
}


///////////////////////////////////////////////////////////////////////////////
// ReleaseData: delete any data allocated by this terrain
void CTerrain::ReleaseData()
{
    delete[] m_Heightmap;
    delete[] m_Patches;
}


///////////////////////////////////////////////////////////////////////////////
// Initialise: initialise this terrain to the given size
// using given heightmap to setup elevation data
bool CTerrain::Initialize(ssize_t patchesPerSide,const u16* data)
{
    // clean up any previous terrain
    ReleaseData();

    // store terrain size
    m_MapSize=patchesPerSide*PATCH_SIZE+1;
    m_MapSizePatches=patchesPerSide;
    // allocate data for new terrain
    m_Heightmap=new u16[m_MapSize*m_MapSize];
    m_Patches=new CPatch[m_MapSizePatches*m_MapSizePatches];

    // given a heightmap?
    if (data) {
        // yes; keep a copy of it
        memcpy(m_Heightmap,data,m_MapSize*m_MapSize*sizeof(u16));
    } else {
        // build a flat terrain
        memset(m_Heightmap,0,m_MapSize*m_MapSize*sizeof(u16));
    }

    // setup patch parents, indices etc
    InitialisePatches();

    return true;
}

///////////////////////////////////////////////////////////////////////////////

CStr8 CTerrain::GetMovementClass(ssize_t i, ssize_t j) const
{
    CMiniPatch* tile = GetTile(i, j);
    if (tile && tile->GetTextureEntry())
        return tile->GetTextureEntry()->GetProperties().GetMovementClass();

    return "default";
}

///////////////////////////////////////////////////////////////////////////////
// CalcPosition: calculate the world space position of the vertex at (i,j)
// If i,j is off the map, it acts as if the edges of the terrain are extended
// outwards to infinity
void CTerrain::CalcPosition(ssize_t i, ssize_t j, CVector3D& pos) const
{
    ssize_t hi = clamp(i, (ssize_t)0, m_MapSize-1);
    ssize_t hj = clamp(j, (ssize_t)0, m_MapSize-1);
    u16 height = m_Heightmap[hj*m_MapSize + hi];
    pos.X = float(i*CELL_SIZE);
    pos.Y = float(height*HEIGHT_SCALE);
    pos.Z = float(j*CELL_SIZE);
}

///////////////////////////////////////////////////////////////////////////////
// CalcPositionFixed: calculate the world space position of the vertex at (i,j)
void CTerrain::CalcPositionFixed(ssize_t i, ssize_t j, CFixedVector3D& pos) const
{
    ssize_t hi = clamp(i, (ssize_t)0, m_MapSize-1);
    ssize_t hj = clamp(j, (ssize_t)0, m_MapSize-1);
    u16 height = m_Heightmap[hj*m_MapSize + hi];
    pos.X = fixed::FromInt(i) * (int)CELL_SIZE;
    pos.Y = fixed::FromInt(height) / (int)HEIGHT_UNITS_PER_METRE;
    pos.Z = fixed::FromInt(j) * (int)CELL_SIZE;
}


///////////////////////////////////////////////////////////////////////////////
// CalcNormal: calculate the world space normal of the vertex at (i,j)
void CTerrain::CalcNormal(ssize_t i, ssize_t j, CVector3D& normal) const
{
    CVector3D left, right, up, down;

    // Calculate normals of the four half-tile triangles surrounding this vertex:

    // get position of vertex where normal is being evaluated
    CVector3D basepos;
    CalcPosition(i, j, basepos);

    if (i > 0) {
        CalcPosition(i-1, j, left);
        left -= basepos;
        left.Normalize();
    }

    if (i < m_MapSize-1) {
        CalcPosition(i+1, j, right);
        right -= basepos;
        right.Normalize();
    }

    if (j > 0) {
        CalcPosition(i, j-1, up);
        up -= basepos;
        up.Normalize();
    }

    if (j < m_MapSize-1) {
        CalcPosition(i, j+1, down);
        down -= basepos;
        down.Normalize();
    }

    CVector3D n0 = up.Cross(left);
    CVector3D n1 = left.Cross(down);
    CVector3D n2 = down.Cross(right);
    CVector3D n3 = right.Cross(up);

    // Compute the mean of the normals
    normal = n0 + n1 + n2 + n3;
    float nlen=normal.Length();
    if (nlen>0.00001f) normal*=1.0f/nlen;
}

///////////////////////////////////////////////////////////////////////////////
// CalcNormalFixed: calculate the world space normal of the vertex at (i,j)
void CTerrain::CalcNormalFixed(ssize_t i, ssize_t j, CFixedVector3D& normal) const
{
    CFixedVector3D left, right, up, down;

    // Calculate normals of the four half-tile triangles surrounding this vertex:

    // get position of vertex where normal is being evaluated
    CFixedVector3D basepos;
    CalcPositionFixed(i, j, basepos);

    if (i > 0) {
        CalcPositionFixed(i-1, j, left);
        left -= basepos;
        left.Normalize();
    }

    if (i < m_MapSize-1) {
        CalcPositionFixed(i+1, j, right);
        right -= basepos;
        right.Normalize();
    }

    if (j > 0) {
        CalcPositionFixed(i, j-1, up);
        up -= basepos;
        up.Normalize();
    }

    if (j < m_MapSize-1) {
        CalcPositionFixed(i, j+1, down);
        down -= basepos;
        down.Normalize();
    }

    CFixedVector3D n0 = up.Cross(left);
    CFixedVector3D n1 = left.Cross(down);
    CFixedVector3D n2 = down.Cross(right);
    CFixedVector3D n3 = right.Cross(up);

    // Compute the mean of the normals
    normal = n0 + n1 + n2 + n3;
    normal.Normalize();
}

CVector3D CTerrain::CalcExactNormal(float x, float z) const
{
    // Clamp to size-2 so we can use the tiles (xi,zi)-(xi+1,zi+1)
    const ssize_t xi = clamp((ssize_t)floor(x/CELL_SIZE), (ssize_t)0, m_MapSize-2);
    const ssize_t zi = clamp((ssize_t)floor(z/CELL_SIZE), (ssize_t)0, m_MapSize-2);

    const float xf = clamp(x/CELL_SIZE-xi, 0.0f, 1.0f);
    const float zf = clamp(z/CELL_SIZE-zi, 0.0f, 1.0f);

    float h00 = m_Heightmap[zi*m_MapSize + xi];
    float h01 = m_Heightmap[(zi+1)*m_MapSize + xi];
    float h10 = m_Heightmap[zi*m_MapSize + (xi+1)];
    float h11 = m_Heightmap[(zi+1)*m_MapSize + (xi+1)];

    // Determine which terrain triangle this point is on,
    // then compute the normal of that triangle's plane

    if (GetTriangulationDir(xi, zi))
    {
        if (xf + zf <= 1.f)
        {
            // Lower-left triangle (don't use h11)
            return -CVector3D(CELL_SIZE, (h10-h00)*HEIGHT_SCALE, 0).Cross(CVector3D(0, (h01-h00)*HEIGHT_SCALE, CELL_SIZE)).Normalized();
        }
        else
        {
            // Upper-right triangle (don't use h00)
            return -CVector3D(CELL_SIZE, (h11-h01)*HEIGHT_SCALE, 0).Cross(CVector3D(0, (h11-h10)*HEIGHT_SCALE, CELL_SIZE)).Normalized();
        }
    }
    else
    {
        if (xf <= zf)
        {
            // Upper-left triangle (don't use h10)
            return -CVector3D(CELL_SIZE, (h11-h01)*HEIGHT_SCALE, 0).Cross(CVector3D(0, (h01-h00)*HEIGHT_SCALE, CELL_SIZE)).Normalized();
        }
        else
        {
            // Lower-right triangle (don't use h01)
            return -CVector3D(CELL_SIZE, (h10-h00)*HEIGHT_SCALE, 0).Cross(CVector3D(0, (h11-h10)*HEIGHT_SCALE, CELL_SIZE)).Normalized();
        }
    }
}

///////////////////////////////////////////////////////////////////////////////
// GetPatch: return the patch at (i,j) in patch space, or null if the patch is
// out of bounds
CPatch* CTerrain::GetPatch(ssize_t i, ssize_t j) const
{
    // range check (invalid indices are passed in by the culling and
    // patch blend code because they iterate from 0..#patches and examine
    // neighbors without checking if they're already on the edge)
    if( (size_t)i >= (size_t)m_MapSizePatches || (size_t)j >= (size_t)m_MapSizePatches )
        return 0;

    return &m_Patches[(j*m_MapSizePatches)+i];
}


///////////////////////////////////////////////////////////////////////////////
// GetTile: return the tile at (i,j) in tile space, or null if the tile is out
// of bounds
CMiniPatch* CTerrain::GetTile(ssize_t i, ssize_t j) const
{
    // see comment above
    if( (size_t)i >= (size_t)(m_MapSize-1) || (size_t)j >= (size_t)(m_MapSize-1) )
        return 0;

    CPatch* patch=GetPatch(i/PATCH_SIZE, j/PATCH_SIZE); // can't fail (due to above check)
    return &patch->m_MiniPatches[j%PATCH_SIZE][i%PATCH_SIZE];
}

float CTerrain::GetVertexGroundLevel(ssize_t i, ssize_t j) const
{
    i = clamp(i, (ssize_t)0, m_MapSize-1);
    j = clamp(j, (ssize_t)0, m_MapSize-1);
    return HEIGHT_SCALE * m_Heightmap[j*m_MapSize + i];
}

fixed CTerrain::GetVertexGroundLevelFixed(ssize_t i, ssize_t j) const
{
    i = clamp(i, (ssize_t)0, m_MapSize-1);
    j = clamp(j, (ssize_t)0, m_MapSize-1);
    // Convert to fixed metres (being careful to avoid intermediate overflows)
    return fixed::FromInt(m_Heightmap[j*m_MapSize + i] / 2) / (int)(HEIGHT_UNITS_PER_METRE / 2);
}

fixed CTerrain::GetSlopeFixed(ssize_t i, ssize_t j) const
{
    // Clamp to size-2 so we can use the tiles (i,j)-(i+1,j+1)
    i = clamp(i, (ssize_t)0, m_MapSize-2);
    j = clamp(j, (ssize_t)0, m_MapSize-2);

    u16 h00 = m_Heightmap[j*m_MapSize + i];
    u16 h01 = m_Heightmap[(j+1)*m_MapSize + i];
    u16 h10 = m_Heightmap[j*m_MapSize + (i+1)];
    u16 h11 = m_Heightmap[(j+1)*m_MapSize + (i+1)];

    // Difference of highest point from lowest point
    u16 delta = std::max(std::max(h00, h01), std::max(h10, h11)) -
                std::min(std::min(h00, h01), std::min(h10, h11));

    // Compute fractional slope (being careful to avoid intermediate overflows)
    return fixed::FromInt(delta / CELL_SIZE) / (int)HEIGHT_UNITS_PER_METRE;
}

float CTerrain::GetExactGroundLevel(float x, float z) const
{
    // Clamp to size-2 so we can use the tiles (xi,zi)-(xi+1,zi+1)
    const ssize_t xi = clamp((ssize_t)floor(x/CELL_SIZE), (ssize_t)0, m_MapSize-2);
    const ssize_t zi = clamp((ssize_t)floor(z/CELL_SIZE), (ssize_t)0, m_MapSize-2);

    const float xf = clamp(x/CELL_SIZE-xi, 0.0f, 1.0f);
    const float zf = clamp(z/CELL_SIZE-zi, 0.0f, 1.0f);

    float h00 = m_Heightmap[zi*m_MapSize + xi];
    float h01 = m_Heightmap[(zi+1)*m_MapSize + xi];
    float h10 = m_Heightmap[zi*m_MapSize + (xi+1)];
    float h11 = m_Heightmap[(zi+1)*m_MapSize + (xi+1)];

    // Determine which terrain triangle this point is on,
    // then compute the linearly-interpolated height on that triangle's plane

    if (GetTriangulationDir(xi, zi))
    {
        if (xf + zf <= 1.f)
        {
            // Lower-left triangle (don't use h11)
            return HEIGHT_SCALE * (h00 + (h10-h00)*xf + (h01-h00)*zf);
        }
        else
        {
            // Upper-right triangle (don't use h00)
            return HEIGHT_SCALE * (h11 + (h01-h11)*(1-xf) + (h10-h11)*(1-zf));
        }
    }
    else
    {
        if (xf <= zf)
        {
            // Upper-left triangle (don't use h10)
            return HEIGHT_SCALE * (h00 + (h11-h01)*xf + (h01-h00)*zf);
        }
        else
        {
            // Lower-right triangle (don't use h01)
            return HEIGHT_SCALE * (h00 + (h10-h00)*xf + (h11-h10)*zf);
        }
    }
}

fixed CTerrain::GetExactGroundLevelFixed(fixed x, fixed z) const
{
    // Clamp to size-2 so we can use the tiles (xi,zi)-(xi+1,zi+1)
    const ssize_t xi = clamp((ssize_t)(x / (int)CELL_SIZE).ToInt_RoundToZero(), (ssize_t)0, m_MapSize-2);
    const ssize_t zi = clamp((ssize_t)(z / (int)CELL_SIZE).ToInt_RoundToZero(), (ssize_t)0, m_MapSize-2);

    const fixed one = fixed::FromInt(1);

    const fixed xf = clamp((x / (int)CELL_SIZE) - fixed::FromInt(xi), fixed::Zero(), one);
    const fixed zf = clamp((z / (int)CELL_SIZE) - fixed::FromInt(zi), fixed::Zero(), one);

    u16 h00 = m_Heightmap[zi*m_MapSize + xi];
    u16 h01 = m_Heightmap[(zi+1)*m_MapSize + xi];
    u16 h10 = m_Heightmap[zi*m_MapSize + (xi+1)];
    u16 h11 = m_Heightmap[(zi+1)*m_MapSize + (xi+1)];

    // Intermediate scaling of xf, so we don't overflow in the multiplications below
    // (h00 <= 65535, xf <= 1, max fixed is < 32768; divide by 2 here so xf1*h00 <= 32767.5)
    const fixed xf0 = xf / 2;
    const fixed xf1 = (one - xf) / 2;

    // Linearly interpolate
    return ((one - zf).Multiply(xf1 * h00 + xf0 * h10)
                  + zf.Multiply(xf1 * h01 + xf0 * h11)) / (int)(HEIGHT_UNITS_PER_METRE / 2);

    // TODO: This should probably be more like GetExactGroundLevel()
    // in handling triangulation properly
}

bool CTerrain::GetTriangulationDir(ssize_t i, ssize_t j) const
{
    // Clamp to size-2 so we can use the tiles (i,j)-(i+1,j+1)
    i = clamp(i, (ssize_t)0, m_MapSize-2);
    j = clamp(j, (ssize_t)0, m_MapSize-2);

    int h00 = m_Heightmap[j*m_MapSize + i];
    int h01 = m_Heightmap[(j+1)*m_MapSize + i];
    int h10 = m_Heightmap[j*m_MapSize + (i+1)];
    int h11 = m_Heightmap[(j+1)*m_MapSize + (i+1)];

    // Prefer triangulating in whichever direction means the midpoint of the diagonal
    // will be the highest. (In particular this means a diagonal edge will be straight
    // along the top, and jagged along the bottom, which makes sense for terrain.)
    int mid1 = h00+h11;
    int mid2 = h01+h10;
    return (mid1 < mid2);
}

///////////////////////////////////////////////////////////////////////////////
// Resize: resize this terrain to the given size (in patches per side)
void CTerrain::Resize(ssize_t size)
{
    if (size==m_MapSizePatches) {
        // inexplicable request to resize terrain to the same size .. ignore it
        return;
    }

    if (!m_Heightmap) {
        // not yet created a terrain; build a default terrain of the given size now
        Initialize(size,0);
        return;
    }

    // allocate data for new terrain
    ssize_t newMapSize=size*PATCH_SIZE+1;
    u16* newHeightmap=new u16[newMapSize*newMapSize];
    CPatch* newPatches=new CPatch[size*size];

    if (size>m_MapSizePatches) {
        // new map is bigger than old one - zero the heightmap so we don't get uninitialised
        // height data along the expanded edges
        memset(newHeightmap,0,newMapSize*newMapSize*sizeof(u16));
    }

    // now copy over rows of data
    u16* src=m_Heightmap;
    u16* dst=newHeightmap;
    ssize_t copysize=std::min(newMapSize, m_MapSize);
    for (ssize_t j=0;j<copysize;j++) {
        memcpy(dst,src,copysize*sizeof(u16));
        dst+=copysize;
        src+=m_MapSize;
        if (newMapSize>m_MapSize) {
            // extend the last height to the end of the row
            for (size_t i=0;i<newMapSize-(size_t)m_MapSize;i++) {
                *dst++=*(src-1);
            }
        }
    }


    if (newMapSize>m_MapSize) {
        // copy over heights of the last row to any remaining rows
        src=newHeightmap+((m_MapSize-1)*newMapSize);
        dst=src+newMapSize;
        for (ssize_t i=0;i<newMapSize-m_MapSize;i++) {
            memcpy(dst,src,newMapSize*sizeof(u16));
            dst+=newMapSize;
        }
    }

    // now build new patches
    for (ssize_t j=0;j<size;j++) {
        for (ssize_t i=0;i<size;i++) {
            // copy over texture data from existing tiles, if possible
            if (i<m_MapSizePatches && j<m_MapSizePatches) {
                memcpy(newPatches[j*size+i].m_MiniPatches,m_Patches[j*m_MapSizePatches+i].m_MiniPatches,sizeof(CMiniPatch)*PATCH_SIZE*PATCH_SIZE);
            }
        }

        if (j<m_MapSizePatches && size>m_MapSizePatches) {
            // copy over the last tile from each column
            for (ssize_t n=0;n<size-m_MapSizePatches;n++) {
                for (ssize_t m=0;m<PATCH_SIZE;m++) {
                    CMiniPatch& src=m_Patches[j*m_MapSizePatches+m_MapSizePatches-1].m_MiniPatches[m][15];
                    for (ssize_t k=0;k<PATCH_SIZE;k++) {
                        CMiniPatch& dst=newPatches[j*size+m_MapSizePatches+n].m_MiniPatches[m][k];
                        dst = src;
                    }
                }
            }
        }
    }

    if (size>m_MapSizePatches) {
        // copy over the last tile from each column
        CPatch* srcpatch=&newPatches[(m_MapSizePatches-1)*size];
        CPatch* dstpatch=srcpatch+size;
        for (ssize_t p=0;p<(ssize_t)size-m_MapSizePatches;p++) {
            for (ssize_t n=0;n<(ssize_t)size;n++) {
                for (ssize_t m=0;m<PATCH_SIZE;m++) {
                    for (ssize_t k=0;k<PATCH_SIZE;k++) {
                        CMiniPatch& src=srcpatch->m_MiniPatches[15][k];
                        CMiniPatch& dst=dstpatch->m_MiniPatches[m][k];
                        dst = src;
                    }
                }
                srcpatch++;
                dstpatch++;
            }
        }
    }


    // release all the original data
    ReleaseData();

    // store new data
    m_Heightmap=newHeightmap;
    m_Patches=newPatches;
    m_MapSize=(ssize_t)newMapSize;
    m_MapSizePatches=(ssize_t)size;

    // initialise all the new patches
    InitialisePatches();
}

///////////////////////////////////////////////////////////////////////////////
// InitialisePatches: initialise patch data
void CTerrain::InitialisePatches()
{
    for (ssize_t j=0;j<m_MapSizePatches;j++) {
        for (ssize_t i=0;i<m_MapSizePatches;i++) {
            CPatch* patch=GetPatch(i,j);    // can't fail
            patch->Initialize(this,i,j);
        }
    }
}

///////////////////////////////////////////////////////////////////////////////
// SetHeightMap: set up a new heightmap from 16-bit source data;
// assumes heightmap matches current terrain size
void CTerrain::SetHeightMap(u16* heightmap)
{
    // keep a copy of the given heightmap
    memcpy(m_Heightmap,heightmap,m_MapSize*m_MapSize*sizeof(u16));

    // recalculate patch bounds, invalidate vertices
    for (ssize_t j=0;j<m_MapSizePatches;j++) {
        for (ssize_t i=0;i<m_MapSizePatches;i++) {
            CPatch* patch=GetPatch(i,j);    // can't fail
            patch->InvalidateBounds();
            patch->SetDirty(RENDERDATA_UPDATE_VERTICES);
        }
    }
}


///////////////////////////////////////////////////////////////////////////////
// FlattenArea: flatten out an area of terrain (specified in world space
// coords); return the average height of the flattened area
float CTerrain::FlattenArea(float x0, float x1, float z0, float z1)
{
    const ssize_t tx0 = clamp(ssize_t(x0/CELL_SIZE),   (ssize_t)0, m_MapSize-1);
    const ssize_t tx1 = clamp(ssize_t(x1/CELL_SIZE)+1, (ssize_t)0, m_MapSize-1);
    const ssize_t tz0 = clamp(ssize_t(z0/CELL_SIZE),   (ssize_t)0, m_MapSize-1);
    const ssize_t tz1 = clamp(ssize_t(z1/CELL_SIZE)+1, (ssize_t)0, m_MapSize-1);

    size_t count=0;
    double sum=0.0f;
    for (ssize_t z=tz0;z<=tz1;z++) {
        for (ssize_t x=tx0;x<=tx1;x++) {
            sum+=m_Heightmap[z*m_MapSize + x];
            count++;
        }
    }
    const u16 avgY = u16(sum/count);

    for (ssize_t z=tz0;z<=tz1;z++) {
        for (ssize_t x=tx0;x<=tx1;x++) {
            m_Heightmap[z*m_MapSize + x]=avgY;
        }
    }

    MakeDirty(tx0, tz0, tx1, tz1, RENDERDATA_UPDATE_VERTICES);

    return avgY*HEIGHT_SCALE;
}

///////////////////////////////////////////////////////////////////////////////

void CTerrain::MakeDirty(ssize_t i0, ssize_t j0, ssize_t i1, ssize_t j1, int dirtyFlags)
{
    // flag vertex data as dirty for affected patches, and rebuild bounds of these patches
    ssize_t pi0 = clamp((i0/PATCH_SIZE)-1, (ssize_t)0, m_MapSizePatches);
    ssize_t pi1 = clamp((i1/PATCH_SIZE)+1, (ssize_t)0, m_MapSizePatches);
    ssize_t pj0 = clamp((j0/PATCH_SIZE)-1, (ssize_t)0, m_MapSizePatches);
    ssize_t pj1 = clamp((j1/PATCH_SIZE)+1, (ssize_t)0, m_MapSizePatches);
    for (ssize_t j = pj0; j < pj1; j++) {
        for (ssize_t i = pi0; i < pi1; i++) {
            CPatch* patch = GetPatch(i,j);  // can't fail (i,j were clamped)
            if (dirtyFlags & RENDERDATA_UPDATE_VERTICES)
                patch->CalcBounds();
            patch->SetDirty(dirtyFlags);
        }
    }
}

void CTerrain::MakeDirty(int dirtyFlags)
{
    for (ssize_t j = 0; j < m_MapSizePatches; j++) {
        for (ssize_t i = 0; i < m_MapSizePatches; i++) {
            CPatch* patch = GetPatch(i,j);  // can't fail
            if (dirtyFlags & RENDERDATA_UPDATE_VERTICES)
                patch->CalcBounds();
            patch->SetDirty(dirtyFlags);
        }
    }
}

CBound CTerrain::GetVertexesBound(ssize_t i0, ssize_t j0, ssize_t i1, ssize_t j1)
{
    i0 = clamp(i0, (ssize_t)0, m_MapSize-1);
    j0 = clamp(j0, (ssize_t)0, m_MapSize-1);
    i1 = clamp(i1, (ssize_t)0, m_MapSize-1);
    j1 = clamp(j1, (ssize_t)0, m_MapSize-1);

    u16 minH = 65535;
    u16 maxH = 0;

    for (ssize_t j = j0; j <= j1; ++j)
    {
        for (ssize_t i = i0; i <= i1; ++i)
        {
            minH = std::min(minH, m_Heightmap[j*m_MapSize + i]);
            maxH = std::max(maxH, m_Heightmap[j*m_MapSize + i]);
        }
    }

    CBound bound;
    bound[0].X = (float)(i0*CELL_SIZE);
    bound[0].Y = (float)(minH*HEIGHT_SCALE);
    bound[0].Z = (float)(j0*CELL_SIZE);
    bound[1].X = (float)(i1*CELL_SIZE);
    bound[1].Y = (float)(maxH*HEIGHT_SCALE);
    bound[1].Z = (float)(j1*CELL_SIZE);
    return bound;
}