选择缓冲区的Z值

Question

用鼠标，对于多个重叠的物体进行选取，照书上的说法，应该使用Z值来判断哪个物体在可视空间中最靠近用户，而进行确定选取。
      可是现在还是不大理解，书上没有相应的例子加以说明。请问谁能够提供相应的例子出来学习吗？谢谢了！！

Answer 1

// ´¦ÀíÑ¡ÔñģʽËù²úÉúµÄ½á¹û¡£ ËÕÓñÑï 2002.2.25.
GLuint WINAPI ProcessSelection(CMyDoc* m_pDoc, GLuint hits, GLuint buffer[], bool bCutTree)
{
unsigned int i;
CString str, strCommand, strDisplay;
GLuint names, *ptr, id, idd;
int z1, z2, zmin;
RECT ChildRect;

ChildRect.left = 100;
ChildRect.right = 400;
ChildRect.top = 100;
ChildRect.bottom = 300;
zmin = -1;
ptr = (GLuint*)buffer;
for(i=0;i<hits;i++)
{
names = *ptr;
ptr++;
z1 = *ptr;
ptr++;
z2 = *ptr;
ptr++;
id = *ptr;
ptr++;
if(id==0)continue;
if(zmin==-1)
{
zmin = z2;
idd = id;
}
else if(z2<zmin)
{
zmin = z2;
idd = id;
}
}
if(bCutTree)return idd;
if(idd<10)
str.Format("0%u", idd);
else
str.Format("%u", idd);

CString strPath;
LPTSTR pszPath;
CString strCommandLine;
LPTSTR pszCommandLine;
  
STARTUPINFO startup;
PROCESS_INFORMATION process;
BOOL tSuccess;   
   
strPath += _T( "hpvfp6vr.exe" );   
memset( &startup, 0, sizeof( startup ) );
startup.cb = sizeof( startup );
startup.dwFlags = STARTF_USESHOWWINDOW|STARTF_USEPOSITION;
startup.wShowWindow = SW_HIDE;
startup.dwX = 400;
startup.dwY = 100;
memset( &process, 0, sizeof( process ) ); strCommandLine.Format( "\"%s\" %s %s", LPCTSTR( strPath ), "2", str);
pszCommandLine = strCommandLine.GetBuffer( 0 );
tSuccess = CreateProcess( NULL, pszCommandLine, NULL, NULL, false,
0, NULL, NULL, &startup, &process );
strCommandLine.ReleaseBuffer();
if( tSuccess )
{
// Close the handles that CreateProcess returned so we don't leak
// kernel resources.
ASSERT( process.hProcess != NULL );
CloseHandle( process.hProcess );
ASSERT( process.hThread != NULL );
CloseHandle( process.hThread );
}
else
{
strDisplay = "hpvfp6vr.exe &Ocirc;&Euml;&ETH;&ETH;&Icirc;&Auml;&frac14;&thorn;&Atilde;&raquo;&Oacute;&ETH;·&cent;&Iuml;&Ouml;&pound;&not;&Ccedil;&euml;&frac14;ì&sup2;é&Acirc;·&frac34;&para;&Ecirc;&Ccedil;·&ntilde;&Otilde;&yacute;&Egrave;·&pound;&not;&Icirc;&Auml;&frac14;&thorn;&Atilde;&ucirc;&Ecirc;&Ccedil;·&ntilde;&Oacute;&ETH;&ETH;§&pound;&iexcl;";
::MessageBox(NULL, strDisplay, "&acute;í&Icirc;ó&pound;&ordm;", MB_OK|MB_ICONQUESTION|MB_SETFOREGROUND);
}/* strCommand.Format("hpvfp6vr %s %s", "2", str);
if(::WinExec(strCommand, SW_HIDE)<=31)
{
strDisplay = "hpvfp6vr.exe &Ocirc;&Euml;&ETH;&ETH;&Icirc;&Auml;&frac14;&thorn;&Atilde;&raquo;&Oacute;&ETH;·&cent;&Iuml;&Ouml;&pound;&not;&Ccedil;&euml;&frac14;ì&sup2;é&Acirc;·&frac34;&para;&Ecirc;&Ccedil;·&ntilde;&Otilde;&yacute;&Egrave;·&pound;&not;&Icirc;&Auml;&frac14;&thorn;&Atilde;&ucirc;&Ecirc;&Ccedil;·&ntilde;&Oacute;&ETH;&ETH;§&pound;&iexcl;";
::MessageBox(NULL, strDisplay, "&acute;í&Icirc;ó&pound;&ordm;", MB_OK|MB_ICONQUESTION|MB_SETFOREGROUND);
} */
return idd;
// str.Format("&Acirc;&yen;·&iquest;&micro;&Auml;&Oacute;&Atilde;&raquo;§&ordm;&Aring;&pound;&ordm;%ld", idd);
// ::MessageBox(NULL, str, "Info", MB_OK | MB_ICONEXCLAMATION);
CBuildingAttriSet BuildingAttriSet(&m_pDoc->m_pCWh->m_database);  // db passed via constructor BuildingAttriSet.m_strFilter.Format("id = '%u'", idd); BuildingAttriSet.m_strFilter="id=?";
str.Format("%u", idd);
BuildingAttriSet.m_idParam = str;
CAttriOperateDlg AttriOperateDlg;

// AttriRecView.OnInitialUpdate();
// AttriRecView.Create(NULL, "&Ecirc;&ocirc;&ETH;&Ocirc;&sup2;&Ugrave;×÷", WS_VISIBLE|WS_POPUP|WS_OVERLAPPEDWINDOW|WS_CLIPCHILDREN, ChildRect, NULL, 0, NULL);
// BuildingAttriSet.m_bUpdatable = true;
BuildingAttriSet.Open();
if(!BuildingAttriSet.IsEOF()) {
AttriOperateDlg.m_iUserID = atol(BuildingAttriSet.m_id);
AttriOperateDlg.m_strZIP = BuildingAttriSet.m_att01;
AttriOperateDlg.m_strProvince = BuildingAttriSet.m_att02;
AttriOperateDlg.m_strCounty = BuildingAttriSet.m_att03;
AttriOperateDlg.m_strStreet = BuildingAttriSet.m_att04;
AttriOperateDlg.m_strCourtyard = BuildingAttriSet.m_att05;
AttriOperateDlg.m_strHouseNo = BuildingAttriSet.m_att06;
AttriOperateDlg.m_iFloor = atol(BuildingAttriSet.m_att07);
AttriOperateDlg.m_strDoorPlate = BuildingAttriSet.m_att08;
AttriOperateDlg.m_strTelephone = BuildingAttriSet.m_att09;
AttriOperateDlg.m_strUser = BuildingAttriSet.m_att10;
AttriOperateDlg.m_strOwner = BuildingAttriSet.m_att11;
AttriOperateDlg.m_strOtherAuthority = BuildingAttriSet.m_att12;
AttriOperateDlg.m_dLandArea = BuildingAttriSet.m_att13;
AttriOperateDlg.m_dUserArea = atof(BuildingAttriSet.m_att14);
AttriOperateDlg.m_dBuildingArea = atof(BuildingAttriSet.m_att15);
AttriOperateDlg.m_strBuildingType = BuildingAttriSet.m_att16;
AttriOperateDlg.m_dBuildingZ = atof(BuildingAttriSet.m_att17);
AttriOperateDlg.m_dSellLandValue = atof(BuildingAttriSet.m_att18);
AttriOperateDlg.m_dTenancyLandValue = atof(BuildingAttriSet.m_att19);
AttriOperateDlg.m_dCenterX = atof(BuildingAttriSet.m_att20);
AttriOperateDlg.m_dCenterY = atof(BuildingAttriSet.m_att21);
AttriOperateDlg.m_dZ = atof(BuildingAttriSet.m_att22);
AttriOperateDlg.m_strClassCode = BuildingAttriSet.m_att23;
AttriOperateDlg.m_strName = BuildingAttriSet.m_att24;

// BuildingAttriSet.MoveNext();
}
else
return 0;
if(AttriOperateDlg.DoModal()==IDOK)
{
// BuildingAttriSet.MoveNext() BuildingAttriSet.Edit();
str.Format("%u", AttriOperateDlg.m_iUserID);
BuildingAttriSet.m_id = str;
BuildingAttriSet.m_att01 = AttriOperateDlg.m_strZIP;
BuildingAttriSet.m_att02 = AttriOperateDlg.m_strProvince;
BuildingAttriSet.m_att03 = AttriOperateDlg.m_strCounty;
BuildingAttriSet.m_att04 = AttriOperateDlg.m_strStreet;
BuildingAttriSet.m_att05 = AttriOperateDlg.m_strCourtyard;
BuildingAttriSet.m_att06 = AttriOperateDlg.m_strHouseNo;
str.Format("%u", AttriOperateDlg.m_iFloor);
BuildingAttriSet.m_att07 = str;
BuildingAttriSet.m_att08 = AttriOperateDlg.m_strDoorPlate;
BuildingAttriSet.m_att09 = AttriOperateDlg.m_strTelephone;
BuildingAttriSet.m_att10 = AttriOperateDlg.m_strUser;
BuildingAttriSet.m_att11 = AttriOperateDlg.m_strOwner;
BuildingAttriSet.m_att12 = AttriOperateDlg.m_strOtherAuthority;
str.Format("%lf", AttriOperateDlg.m_dLandArea);
BuildingAttriSet.m_att13 = str;
str.Format("%lf", AttriOperateDlg.m_dUserArea);
BuildingAttriSet.m_att14 = str;
str.Format("%lf", AttriOperateDlg.m_dBuildingArea);
BuildingAttriSet.m_att15 = str;
AttriOperateDlg.m_strBuildingType = BuildingAttriSet.m_att16;
str.Format("%lf", AttriOperateDlg.m_dBuildingZ);
BuildingAttriSet.m_att17 = str;
str.Format("%lf", AttriOperateDlg.m_dSellLandValue);
BuildingAttriSet.m_att18 = str;
str.Format("%lf", AttriOperateDlg.m_dTenancyLandValue);
BuildingAttriSet.m_att19 = str;
str.Format("%lf", AttriOperateDlg.m_dCenterX);
BuildingAttriSet.m_att20 = str;
str.Format("%lf", AttriOperateDlg.m_dCenterY);
BuildingAttriSet.m_att21 = str;
str.Format("%lf", AttriOperateDlg.m_dZ);
BuildingAttriSet.m_att22 = str;
BuildingAttriSet.m_att23 = AttriOperateDlg.m_strClassCode;
BuildingAttriSet.m_att24 = AttriOperateDlg.m_strName;

if(BuildingAttriSet.CanUpdate())BuildingAttriSet.Update();
// AttriOperateDlg.UpdateData(true);
}
if(BuildingAttriSet.IsOpen())
{
BuildingAttriSet.Close();
}
return idd;
}