Isometric Game Programming with DirectX 7.0/Isometric Game Programming.iso/source/chapter21/isohex21_2/isorenderer.cpp

C/C++ Source or Header | 2000-08-18 | 18.7 KB | 671 lines

//IsoRenderer.cpp

#include "IsoRenderer.h"
#include "DDFuncs.h"

//constructor
CRenderer::CRenderer()
{
    //blank
}

CRenderer::~CRenderer()
{
    //deallocate rectangle list
    delete rcUpdateList;
    //deallocate update map
    delete bMap;
}

//surfaces
void CRenderer::SetBackBuffer(LPDIRECTDRAWSURFACE7 lpdds)
{
    //set the back buffer
    lpddsBackBuffer=lpdds;
}

void CRenderer::SetFrameBuffer(LPDIRECTDRAWSURFACE7 lpdds)
{
    //set the frame buffer
    lpddsFrameBuffer=lpdds;
}

//isohexcore components
void CRenderer::SetPlotter(CTilePlotter* pPlotter)
{
    //set the plotter
    pTilePlotter=pPlotter;
}

void CRenderer::SetWalker(CTileWalker* pWalker)
{
    //set the tile walker
    pTileWalker=pWalker;
}

void CRenderer::SetMouseMap(CMouseMap* pMMap)
{
    //set the mousemap
    pMouseMap=pMMap;
}

void CRenderer::SetScroller(CScroller* pScroll)
{
    //set the scroller
    pScroller=pScroll;
}

//update list
void CRenderer::SetUpdateRectCount(int iMaxRects)//sets up the rectangle list
{
    //set the max number of rectangles
    iUpdateRectCount=iMaxRects;
    //allocate the rectangle list
    rcUpdateList=new RECT[iMaxRects];
    //set the index to 0
    iUpdateRectIndex=0;
}

//update map
void CRenderer::SetMapSize(int MapWidth,int MapHeight)//sets up the update map
{
    //allocate a new map
    bMap=new bool[MapWidth*MapHeight];

    //set the map width and height
    iMapWidth=MapWidth;
    iMapHeight=MapHeight;
}

//rendering functions
void CRenderer::SetRenderFunction(RENDERFN RendFunc)
{
    //set the rendering function
    RenderFunction=RendFunc;
}

//extent rect
void CRenderer::SetExtentRect(RECT* rcExt)
{
    CopyRect(&rcExtent,rcExt);
}

//add rect to list
void CRenderer::AddRect(RECT* prcAdd)
{
    //if there is no more room in the rectangle list, return
    if(iUpdateRectIndex>=iUpdateRectCount) return;

    //copy rect
    RECT rcUpdate;
    IntersectRect(&rcUpdate,prcAdd,pScroller->GetScreenSpace());
    //if the update rect is empty, return
    if(IsRectEmpty(&rcUpdate)) return;

    //clear out the frame buffer with black in the update region
    DDBLTFX ddbltfx;
    DDBLTFX_ColorFill(&ddbltfx,0);
    lpddsFrameBuffer->Blt(&rcUpdate,NULL,NULL,DDBLT_WAIT | DDBLT_COLORFILL,&ddbltfx);

    //add the rect to the list
    CopyRect(&rcUpdateList[iUpdateRectIndex],&rcUpdate);
    iUpdateRectIndex++;//add one to the index

    //temp variables for calculations
    POINT ptTemp;
    POINT ptCoarse;
    POINT ptMap;

    //calculate the corner points
    POINT ptCornerUpperLeft;
    POINT ptCornerUpperRight;
    POINT ptCornerLowerLeft;
    POINT ptCornerLowerRight;

    //upper left
    ptTemp.x=rcUpdate.left;
    ptTemp.y=rcUpdate.top;
    //screen->world
    ptTemp=pScroller->ScreenToWorld(ptTemp);
    //subtract mousemap reference point
    ptTemp.x-=pMouseMap->GetReferencePoint()->x;
    ptTemp.y-=pMouseMap->GetReferencePoint()->y;
    //calculate coarse coordinates
    ptCoarse.x=ptTemp.x/pMouseMap->GetWidth();
    ptCoarse.y=ptTemp.y/pMouseMap->GetHeight();
    //calculate fine cordinates
    ptTemp.x%=pMouseMap->GetWidth();
    ptTemp.y%=pMouseMap->GetHeight();
    //check for negative fine coordinates
    if(ptTemp.x<0) ptCoarse.x--;
    if(ptTemp.y<0) ptCoarse.y--;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the east
    ptMap=pTileWalker->TileWalk(ptMap,ISO_EAST);
    //assign the corner point
    ptCornerUpperLeft.x=ptMap.x*ptCoarse.x;
    ptCornerUpperLeft.y=ptMap.y*ptCoarse.x;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the south
    ptMap=pTileWalker->TileWalk(ptMap,ISO_SOUTH);
    ptCornerUpperLeft.x+=(ptMap.x*ptCoarse.y);
    ptCornerUpperLeft.y+=(ptMap.y*ptCoarse.y);

    //upper right
    ptTemp.x=rcUpdate.right;
    ptTemp.y=rcUpdate.top;
    //screen->world
    ptTemp=pScroller->ScreenToWorld(ptTemp);
    //subtract mousemap reference point
    ptTemp.x-=pMouseMap->GetReferencePoint()->x;
    ptTemp.y-=pMouseMap->GetReferencePoint()->y;
    //calculate coarse coordinates
    ptCoarse.x=ptTemp.x/pMouseMap->GetWidth();
    ptCoarse.y=ptTemp.y/pMouseMap->GetHeight();
    //calculate fine cordinates
    ptTemp.x%=pMouseMap->GetWidth();
    ptTemp.y%=pMouseMap->GetHeight();
    //check for negative fine coordinates
    if(ptTemp.x<0) ptCoarse.x--;
    if(ptTemp.y<0) ptCoarse.y--;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the east
    ptMap=pTileWalker->TileWalk(ptMap,ISO_EAST);
    //assign the corner point
    ptCornerUpperRight.x=ptMap.x*ptCoarse.x;
    ptCornerUpperRight.y=ptMap.y*ptCoarse.x;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the south
    ptMap=pTileWalker->TileWalk(ptMap,ISO_SOUTH);
    ptCornerUpperRight.x+=(ptMap.x*ptCoarse.y);
    ptCornerUpperRight.y+=(ptMap.y*ptCoarse.y);

    //lower left
    ptTemp.x=rcUpdate.left;
    ptTemp.y=rcUpdate.bottom;
    //screen->world
    ptTemp=pScroller->ScreenToWorld(ptTemp);
    //subtract mousemap reference point
    ptTemp.x-=pMouseMap->GetReferencePoint()->x;
    ptTemp.y-=pMouseMap->GetReferencePoint()->y;
    //calculate coarse coordinates
    ptCoarse.x=ptTemp.x/pMouseMap->GetWidth();
    ptCoarse.y=ptTemp.y/pMouseMap->GetHeight();
    //calculate fine cordinates
    ptTemp.x%=pMouseMap->GetWidth();
    ptTemp.y%=pMouseMap->GetHeight();
    //check for negative fine coordinates
    if(ptTemp.x<0) ptCoarse.x--;
    if(ptTemp.y<0) ptCoarse.y--;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the east
    ptMap=pTileWalker->TileWalk(ptMap,ISO_EAST);
    //assign the corner point
    ptCornerLowerLeft.x=ptMap.x*ptCoarse.x;
    ptCornerLowerLeft.y=ptMap.y*ptCoarse.x;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the south
    ptMap=pTileWalker->TileWalk(ptMap,ISO_SOUTH);
    ptCornerLowerLeft.x+=(ptMap.x*ptCoarse.y);
    ptCornerLowerLeft.y+=(ptMap.y*ptCoarse.y);

    //lower right
    ptTemp.x=rcUpdate.right;
    ptTemp.y=rcUpdate.bottom;
    //screen->world
    ptTemp=pScroller->ScreenToWorld(ptTemp);
    //subtract mousemap reference point
    ptTemp.x-=pMouseMap->GetReferencePoint()->x;
    ptTemp.y-=pMouseMap->GetReferencePoint()->y;
    //calculate coarse coordinates
    ptCoarse.x=ptTemp.x/pMouseMap->GetWidth();
    ptCoarse.y=ptTemp.y/pMouseMap->GetHeight();
    //calculate fine cordinates
    ptTemp.x%=pMouseMap->GetWidth();
    ptTemp.y%=pMouseMap->GetHeight();
    //check for negative fine coordinates
    if(ptTemp.x<0) ptCoarse.x--;
    if(ptTemp.y<0) ptCoarse.y--;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the east
    ptMap=pTileWalker->TileWalk(ptMap,ISO_EAST);
    //assign the corner point
    ptCornerLowerRight.x=ptMap.x*ptCoarse.x;
    ptCornerLowerRight.y=ptMap.y*ptCoarse.x;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the south
    ptMap=pTileWalker->TileWalk(ptMap,ISO_SOUTH);
    ptCornerLowerRight.x+=(ptMap.x*ptCoarse.y);
    ptCornerLowerRight.y+=(ptMap.y*ptCoarse.y);

    //move the corners away from screenspace one step
    ptCornerUpperLeft=pTileWalker->TileWalk(ptCornerUpperLeft,ISO_NORTHWEST);
    ptCornerUpperRight=pTileWalker->TileWalk(ptCornerUpperRight,ISO_NORTHEAST);
    ptCornerLowerLeft=pTileWalker->TileWalk(ptCornerLowerLeft,ISO_SOUTHWEST);
    ptCornerLowerRight=pTileWalker->TileWalk(ptCornerLowerRight,ISO_SOUTHEAST);

    //move the left corners to the west
    ptCornerUpperLeft=pTileWalker->TileWalk(ptCornerUpperLeft,ISO_WEST);
    ptCornerLowerLeft=pTileWalker->TileWalk(ptCornerLowerLeft,ISO_WEST);

    //move the bottom corners to the south
    ptCornerLowerLeft=pTileWalker->TileWalk(ptCornerLowerLeft,ISO_SOUTH);
    ptCornerLowerRight=pTileWalker->TileWalk(ptCornerLowerRight,ISO_SOUTH);

    //scan through the tiles
    POINT ptRowStart=ptCornerUpperLeft;
    POINT ptRowEnd=ptCornerUpperRight;
    POINT ptCurrent=ptRowStart;
    DWORD dwRowCount=0;
    for(;;)
    {
        //set current point to rowstart
        ptCurrent=ptRowStart;

        //render a row of tiles
        for(;;)
        {
            //check that ptcurrent is an actual map location
            if(ptCurrent.x>=0 && ptCurrent.y>=0 && ptCurrent.x<iMapWidth && ptCurrent.y<iMapHeight)
            {
                //mark tile for updating
                bMap[ptCurrent.x+ptCurrent.y*iMapWidth]=true;
            }

            //is this the last tile in the row?
            if(ptCurrent.x==ptRowEnd.x && ptCurrent.y==ptRowEnd.y) break;

            //walk to the east
            ptCurrent=pTileWalker->TileWalk(ptCurrent,ISO_EAST);

        }

        //check to see if this is the last row
        if(ptRowStart.x==ptCornerLowerLeft.x && ptRowStart.y==ptCornerLowerLeft.y) break;

        //move down a row
        if(dwRowCount&1)
        {
            //odd row
            //move outward
            ptRowStart=pTileWalker->TileWalk(ptRowStart,ISO_SOUTHWEST);
            ptRowEnd=pTileWalker->TileWalk(ptRowEnd,ISO_SOUTHEAST);
        }
        else
        {
            //even row
            //move inward
            ptRowStart=pTileWalker->TileWalk(ptRowStart,ISO_SOUTHEAST);
            ptRowEnd=pTileWalker->TileWalk(ptRowEnd,ISO_SOUTHWEST);
        }

        //add one to the row count
        dwRowCount++;
    }
}

void CRenderer::AddTile(int mapx,int mapy)
{
    //put x and y into a point
    POINT ptMap;
    ptMap.x=mapx;
    ptMap.y=mapy;
    //plot the map coord
    POINT ptPlot=pTilePlotter->PlotTile(ptMap);
    //convert to screen coords
    ptPlot=pScroller->WorldToScreen(ptPlot);
    //get ext rect
    RECT rcUpdate;
    CopyRect(&rcUpdate,&rcExtent);
    //offset by plotted point
    OffsetRect(&rcUpdate,ptPlot.x,ptPlot.y);
    //add to rect list
    AddRect(&rcUpdate);
}

//scroll the frame
void CRenderer::ScrollFrame(int scrollx,int scrolly)
{
    //figure out the actual scrollx and scrolly
    POINT ptAnchorOld;
    //grab the current anchor position
    ptAnchorOld.x=pScroller->GetAnchor()->x;
    ptAnchorOld.y=pScroller->GetAnchor()->y;
    //move the anchor
    pScroller->MoveAnchor(scrollx,scrolly);
    //calculate the actual scrollx and scrolly
    scrollx=pScroller->GetAnchor()->x-ptAnchorOld.x;
    scrolly=pScroller->GetAnchor()->y-ptAnchorOld.y;
    //reset the anchor position
    pScroller->GetAnchor()->x=ptAnchorOld.x;
    pScroller->GetAnchor()->y=ptAnchorOld.y;

    //rectangle for blitting
    RECT rcSrc;//source RECT(frame buffer)
    RECT rcDst;//destination RECT(back buffer)
    RECT rcUpdateX;//update rect
    RECT rcUpdateY;//update rect
    //set both rects to the screen space
    CopyRect(&rcSrc,pScroller->GetScreenSpace());
    CopyRect(&rcDst,pScroller->GetScreenSpace());
    //set both update rects empty
    SetRectEmpty(&rcUpdateX);
    SetRectEmpty(&rcUpdateY);
    //check the sign of scrollx
    //if scrollx is 0, we need do nothing
    if(scrollx)
    {
        //scrollx is non-zero
        if(scrollx<0)
        {
            //positive scrollx
            //scroll direction: to the right
            //set up an update rect for the left side of the screen
            SetRect(&rcUpdateX,rcDst.left,rcDst.top,rcDst.left-scrollx,rcDst.bottom);
            //adjust the blitting rects
            rcDst.left-=scrollx;
            rcSrc.right+=scrollx;
        }
        else
        {
            //negative scrollx
            //scroll direction: to the left
            //set up an update rect for the right side of the screen
            SetRect(&rcUpdateX,rcDst.right-scrollx,rcDst.top,rcDst.right,rcDst.bottom);
            //adjust the blitting rects
            rcDst.right-=scrollx;
            rcSrc.left+=scrollx;
        }
    }
    //check the sign of scrolly
    //if scrolly is 0, we need do nothing
    if(scrolly)
    {
        //scrolly is non-zero
        if(scrolly<0)
        {
            //negative scrolly
            //scroll direction: down
            //set and update rect for the top of the screen
            SetRect(&rcUpdateY,rcDst.left,rcDst.top,rcDst.right,rcDst.top-scrolly);
            //adjust the blitting rects
            rcDst.top-=scrolly;
            rcSrc.bottom+=scrolly;
        }
        else
        {
            //positive scrolly
            //scroll direction: up
            //set an update rect for the bottom of the screen
            SetRect(&rcUpdateY,rcDst.left,rcDst.bottom-scrolly,rcDst.right,rcDst.bottom);
            //adjust the blitting rects
            rcDst.bottom-=scrolly;
            rcSrc.top+=scrolly;
        }
    }
    //perform the blit(bulk scrolling)
    lpddsBackBuffer->BltFast(rcDst.left,rcDst.top,lpddsFrameBuffer,&rcSrc,DDBLTFAST_WAIT);
    //perform the scroll
    pScroller->MoveAnchor(scrollx,scrolly);
    //add the update rects
    AddRect(&rcUpdateX);
    AddRect(&rcUpdateY);
}

//update the frame
void CRenderer::UpdateFrame()
{
    //update rect
    RECT rcUpdate;
    //copy from screenspace
    CopyRect(&rcUpdate,pScroller->GetScreenSpace());

    //temp variables for calculations
    POINT ptTemp;
    POINT ptCoarse;
    POINT ptMap;
    POINT ptPlot;

    //calculate the corner points
    POINT ptCornerUpperLeft;
    POINT ptCornerUpperRight;
    POINT ptCornerLowerLeft;
    POINT ptCornerLowerRight;

    //upper left
    ptTemp.x=rcUpdate.left;
    ptTemp.y=rcUpdate.top;
    //screen->world
    ptTemp=pScroller->ScreenToWorld(ptTemp);
    //subtract mousemap reference point
    ptTemp.x-=pMouseMap->GetReferencePoint()->x;
    ptTemp.y-=pMouseMap->GetReferencePoint()->y;
    //calculate coarse coordinates
    ptCoarse.x=ptTemp.x/pMouseMap->GetWidth();
    ptCoarse.y=ptTemp.y/pMouseMap->GetHeight();
    //calculate fine cordinates
    ptTemp.x%=pMouseMap->GetWidth();
    ptTemp.y%=pMouseMap->GetHeight();
    //check for negative fine coordinates
    if(ptTemp.x<0) ptCoarse.x--;
    if(ptTemp.y<0) ptCoarse.y--;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the east
    ptMap=pTileWalker->TileWalk(ptMap,ISO_EAST);
    //assign the corner point
    ptCornerUpperLeft.x=ptMap.x*ptCoarse.x;
    ptCornerUpperLeft.y=ptMap.y*ptCoarse.x;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the south
    ptMap=pTileWalker->TileWalk(ptMap,ISO_SOUTH);
    ptCornerUpperLeft.x+=(ptMap.x*ptCoarse.y);
    ptCornerUpperLeft.y+=(ptMap.y*ptCoarse.y);

    //upper right
    ptTemp.x=rcUpdate.right;
    ptTemp.y=rcUpdate.top;
    //screen->world
    ptTemp=pScroller->ScreenToWorld(ptTemp);
    //subtract mousemap reference point
    ptTemp.x-=pMouseMap->GetReferencePoint()->x;
    ptTemp.y-=pMouseMap->GetReferencePoint()->y;
    //calculate coarse coordinates
    ptCoarse.x=ptTemp.x/pMouseMap->GetWidth();
    ptCoarse.y=ptTemp.y/pMouseMap->GetHeight();
    //calculate fine cordinates
    ptTemp.x%=pMouseMap->GetWidth();
    ptTemp.y%=pMouseMap->GetHeight();
    //check for negative fine coordinates
    if(ptTemp.x<0) ptCoarse.x--;
    if(ptTemp.y<0) ptCoarse.y--;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the east
    ptMap=pTileWalker->TileWalk(ptMap,ISO_EAST);
    //assign the corner point
    ptCornerUpperRight.x=ptMap.x*ptCoarse.x;
    ptCornerUpperRight.y=ptMap.y*ptCoarse.x;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the south
    ptMap=pTileWalker->TileWalk(ptMap,ISO_SOUTH);
    ptCornerUpperRight.x+=(ptMap.x*ptCoarse.y);
    ptCornerUpperRight.y+=(ptMap.y*ptCoarse.y);

    //lower left
    ptTemp.x=rcUpdate.left;
    ptTemp.y=rcUpdate.bottom;
    //screen->world
    ptTemp=pScroller->ScreenToWorld(ptTemp);
    //subtract mousemap reference point
    ptTemp.x-=pMouseMap->GetReferencePoint()->x;
    ptTemp.y-=pMouseMap->GetReferencePoint()->y;
    //calculate coarse coordinates
    ptCoarse.x=ptTemp.x/pMouseMap->GetWidth();
    ptCoarse.y=ptTemp.y/pMouseMap->GetHeight();
    //calculate fine cordinates
    ptTemp.x%=pMouseMap->GetWidth();
    ptTemp.y%=pMouseMap->GetHeight();
    //check for negative fine coordinates
    if(ptTemp.x<0) ptCoarse.x--;
    if(ptTemp.y<0) ptCoarse.y--;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the east
    ptMap=pTileWalker->TileWalk(ptMap,ISO_EAST);
    //assign the corner point
    ptCornerLowerLeft.x=ptMap.x*ptCoarse.x;
    ptCornerLowerLeft.y=ptMap.y*ptCoarse.x;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the south
    ptMap=pTileWalker->TileWalk(ptMap,ISO_SOUTH);
    ptCornerLowerLeft.x+=(ptMap.x*ptCoarse.y);
    ptCornerLowerLeft.y+=(ptMap.y*ptCoarse.y);

    //lower right
    ptTemp.x=rcUpdate.right;
    ptTemp.y=rcUpdate.bottom;
    //screen->world
    ptTemp=pScroller->ScreenToWorld(ptTemp);
    //subtract mousemap reference point
    ptTemp.x-=pMouseMap->GetReferencePoint()->x;
    ptTemp.y-=pMouseMap->GetReferencePoint()->y;
    //calculate coarse coordinates
    ptCoarse.x=ptTemp.x/pMouseMap->GetWidth();
    ptCoarse.y=ptTemp.y/pMouseMap->GetHeight();
    //calculate fine cordinates
    ptTemp.x%=pMouseMap->GetWidth();
    ptTemp.y%=pMouseMap->GetHeight();
    //check for negative fine coordinates
    if(ptTemp.x<0) ptCoarse.x--;
    if(ptTemp.y<0) ptCoarse.y--;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the east
    ptMap=pTileWalker->TileWalk(ptMap,ISO_EAST);
    //assign the corner point
    ptCornerLowerRight.x=ptMap.x*ptCoarse.x;
    ptCornerLowerRight.y=ptMap.y*ptCoarse.x;
    //reset map point
    ptMap.x=0;
    ptMap.y=0;
    //move to the south
    ptMap=pTileWalker->TileWalk(ptMap,ISO_SOUTH);
    ptCornerLowerRight.x+=(ptMap.x*ptCoarse.y);
    ptCornerLowerRight.y+=(ptMap.y*ptCoarse.y);

    //move the corners away from screenspace one step
    ptCornerUpperLeft=pTileWalker->TileWalk(ptCornerUpperLeft,ISO_NORTHWEST);
    ptCornerUpperRight=pTileWalker->TileWalk(ptCornerUpperRight,ISO_NORTHEAST);
    ptCornerLowerLeft=pTileWalker->TileWalk(ptCornerLowerLeft,ISO_SOUTHWEST);
    ptCornerLowerRight=pTileWalker->TileWalk(ptCornerLowerRight,ISO_SOUTHEAST);

    //move the left corners to the west
    ptCornerUpperLeft=pTileWalker->TileWalk(ptCornerUpperLeft,ISO_WEST);
    ptCornerLowerLeft=pTileWalker->TileWalk(ptCornerLowerLeft,ISO_WEST);

    //move the bottom corners to the south
    ptCornerLowerLeft=pTileWalker->TileWalk(ptCornerLowerLeft,ISO_SOUTH);
    ptCornerLowerRight=pTileWalker->TileWalk(ptCornerLowerRight,ISO_SOUTH);

    //scan through the tiles
    POINT ptRowStart=ptCornerUpperLeft;
    POINT ptRowEnd=ptCornerUpperRight;
    POINT ptCurrent=ptRowStart;
    DWORD dwRowCount=0;
    for(;;)
    {
        //set current point to rowstart
        ptCurrent=ptRowStart;

        //render a row of tiles
        for(;;)
        {
            //plot the tile
            ptPlot=pTilePlotter->PlotTile(ptCurrent);
            ptPlot=pScroller->WorldToScreen(ptPlot);
            //check that ptcurrent is an actual map location
            if(ptCurrent.x>=0 && ptCurrent.y>=0 && ptCurrent.x<iMapWidth && ptCurrent.y<iMapHeight)
            {
                //is the tile marked?
                if(bMap[ptCurrent.x+ptCurrent.y*iMapWidth])
                {
                    //send to rendering function
                    RenderFunction(lpddsFrameBuffer,&rcUpdate,ptPlot.x,ptPlot.y,ptCurrent.x,ptCurrent.y);
                    //rest to unmarked
                    bMap[ptCurrent.x+ptCurrent.y*iMapWidth]=false;
                }
            }

            //is this the last tile in the row?
            if(ptCurrent.x==ptRowEnd.x && ptCurrent.y==ptRowEnd.y) break;

            //walk to the east
            ptCurrent=pTileWalker->TileWalk(ptCurrent,ISO_EAST);

        }

        //check to see if this is the last row
        if(ptRowStart.x==ptCornerLowerLeft.x && ptRowStart.y==ptCornerLowerLeft.y) break;

        //move down a row
        if(dwRowCount&1)
        {
            //odd row
            //move outward
            ptRowStart=pTileWalker->TileWalk(ptRowStart,ISO_SOUTHWEST);
            ptRowEnd=pTileWalker->TileWalk(ptRowEnd,ISO_SOUTHEAST);
        }
        else
        {
            //even row
            //move inward
            ptRowStart=pTileWalker->TileWalk(ptRowStart,ISO_SOUTHEAST);
            ptRowEnd=pTileWalker->TileWalk(ptRowEnd,ISO_SOUTHWEST);
        }

        //add one to the row count
        dwRowCount++;
    }

    //render all update rects from frame buffer to back buffer
    for(int iCount=0;iCount<iUpdateRectIndex;iCount++)
    {
        //render update rect
        lpddsBackBuffer->BltFast(rcUpdateList[iCount].left,rcUpdateList[iCount].top,lpddsFrameBuffer,&rcUpdateList[iCount],DDBLTFAST_WAIT);
    }

    //render from back buffer to frame buffer
    lpddsFrameBuffer->BltFast(rcUpdate.left,rcUpdate.top,lpddsBackBuffer,&rcUpdate,DDBLTFAST_WAIT);

    //set rectangle index to 0
    iUpdateRectIndex=0;
}