请教OPENGL捕获坐标问题！

syy64(太平洋)：能把你的思路说说看吗？你是如何取屏幕中所绘的节点的。如果我绘的节点坐标是x=2.2222,y=3.3333,z=4.4444（从数据文件中读出）,那么捕获的该点坐标是否和数据文件中的坐标一致，会不会有误差？能不能帮人帮到底，解释的清楚一些，多谢了。

到http://www.codeguru.com/Cpp/G-M/opengl/不知道可否帮你。

to DentistryDoctor(牙科医生):是“A 3D Object Picking Technique that Uses OpenGL”这个例子吗，我回去看看，但是问syy64(太平洋)的问题也得明白啊。

不好意思，出差刚回来；
“另外我所画的点连线，所有点都是有序号的，如何返回捕获点的序号呢”，那得通过选择模式，看《超级宝典》；
“如果我绘的节点坐标是x=2.2222,y=3.3333,z=4.4444（从数据文件中读出）,那么捕获的该点坐标是否和数据文件中的坐标一致，会不会有误差？”，那肯定是有。

TO SYY64：那你是否要将捕获的坐标和数据文件（数组中保存的节点信息）进行比较，数据相近的就将该点的节点号返回对吗？
m_dModelMinX,m_dModelMaxX是屏幕中绘制的最大坐标最小坐标吗，比如我数据文件中的某点坐标值是100，200，300，而画到屏幕中的OPENGL坐标值是限定在-10到10的范围里了那么m_dModelMinX,m_dModelMaxX就是-10和10对吗？
dMouseModelX是什么意思，我是在VIEW类里定义的，是否可以不需要定义m_pDoc文档类指针？

不是这样的，不用比较，返回节点号是用选择模式；
不是，m_dModelMinX,m_dModelMaxX是场景中所有模型的范围；
可以不需要定义m_pDoc文档类指针；
哥们，你的信誉值咋那么低？

详细说说选择模式好吗？我不太明白，那现在这种是什么方式，以后我还需要实现捕获线段，我现在脑袋都大了，OPENGL我也不是很熟，工作还比较急，你耐心仔细给我讲讲如何？信誉值低的原因我也不清楚，我提了不少问题到现在为止只有8个没给分，而且我也不知道怎么把信誉值提高。以前提的问题你回答的我不是都给分了吗？
m_dModelMinX,m_dModelMaxX是场景中所有模型的范围，那么就是说是我画的图形的各个节点的X轴最小值和最大值吗？我现在做的程序的流程是读取一个文本文件去画图，文本文件的内容是有节点的ID号（也就是序号），和该点的三维坐标X，Y，Z，还有节点的连线关系。例如下面格式：
ID     X       Y       Z
1      0.1    2.0    4.56
2      8.5    3.333  9.0000
3      ................
4      ................
5      ................
6      ................
7      ................
8      ................
1-2 2-3 4-5.......                    --->连线关系，比如1点和2点连，2点和3点连
我根据连线关系画出所有线段。
那么在屏幕中点中该节点要求反馈回该点的坐标和序号。需要在保存上述数据的数组中搜索符合的数据吗，你是怎么实现捕获节点的。能详细说说吗，多谢。比如你给段代码给点注释和说明，因为我对OPENGL还不是太熟悉。另外如果分不够可以再给，怎么给你告诉我。还有怎么增加信誉分？

openGL有三种模式，运行模式、选择模式、和反馈模式，要获取坐标，得通过反馈模式；
m_dModelMinX,m_dModelMaxX是场景中所有模型的范围，那么就是说是你画的图形的中X轴最小值和最大值；
建议你好好看看OPENGL书，如《超级宝典》和红宝书；
我手头的事情比较多，只能给你提供思路，别的实在力不从心，望见谅。

dMouseModelX是什么含义.
我把所有读取的X,Y,Z轴坐标都通过算法把范围定在-10到10以内了(为了将不同坐标范围得图形画到屏幕以内,我屏幕内得场景坐标范围定得是-10到10),那么m_dModelMinX等变量也是这样吗?比如我图形里最小X轴坐标是100但是同意经过放大或缩小变成了10,那么m_dModelMinX就等于10是吗

dMouseModelX是在当前的前面用gluunProject得到的鼠标有效的（在场景范围内）空间坐标值；
根据你的情况，m_dModelMinX应该为-10，m_dModelMaxX应该为10。

我看我的问题还没解决，太平洋兄多谢能给我提供两个关于反馈模式的例子程序看看吗，连接地址也行，我的信箱：[email protected]，回完这个贴我就把分给你结了。

// Select.c
// OpenGL SuperBible, Chapter 14
// Demonstrates OpenGL Picking and Selection with feedback
// Program by Richard S. Wright Jr.#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glut.h>
#include <math.h>#define glRGB(x, y, z) glColor3ub((GLubyte)x, (GLubyte)y, (GLubyte)z)#define CUBE 1
#define SPHERE 2

RECT bRect; // Bounding rectangle
GLuint nWho = 0; // Who is selected
float fAspect;// Application name and instance storeage
static LPCTSTR lpszAppName = "Select an Object";
static HINSTANCE hInstance;// Lighting values
GLfloat  whiteLight[] = { 0.35f, 0.35f, 0.35f, 1.0f };
GLfloat  sourceLight[] = { 0.65f, 0.65f, 0.65f, 1.0f };
GLfloat lightPos[] = { -500.0f, 500.0f, 600.0f, 1.0f };// Render the cube and sphere
void DrawObjects(void)
{
// Save the matrix state and do the rotations
glMatrixMode(GL_MODELVIEW);
glPushMatrix(); // Translate the whole scene out and into view
glTranslatef(-80.0f, 0.0f, -300.0f); // Initialize the names stack
glInitNames();
glPushName(0); // Set material color, Yellow
// Cube
glRGB(255, 255, 0);
glLoadName(CUBE);
glPassThrough((GLfloat)CUBE);
glutSolidCube(75.0f);
// Draw Sphere
glRGB(128,0,0);
glTranslatef(130.0f, 0.0f, 0.0f);
glLoadName(SPHERE);
glPassThrough((GLfloat)SPHERE);
glutSolidSphere(50.0f, 15, 15); // Restore the matrix state
glPopMatrix(); // Modelview matrix
}
// Called to draw scene
void RenderScene(void)
{
// Clear the window with current clearing color
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

// Draw the objects in the scene
DrawObjects(); // If something is selected, draw a bounding box around it
if(nWho != 0)
{
int viewport[4];

// Get the viewport
glGetIntegerv(GL_VIEWPORT, viewport); // Remap the viewing volume to match window coordinates (approximately)
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();

// Establish clipping volume (left, right, bottom, top, near, far)
glOrtho(viewport[0], viewport[2], viewport[3], viewport[1], -1, 1);
glMatrixMode(GL_MODELVIEW); glDisable(GL_LIGHTING);
glColor3ub(255,0,0);
glBegin(GL_LINE_LOOP);
glVertex2i(bRect.left, bRect.top);
glVertex2i(bRect.left, bRect.bottom);
glVertex2i(bRect.right, bRect.bottom);
glVertex2i(bRect.right, bRect.top);
glEnd();
glEnable(GL_LIGHTING);
} glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW); glutSwapBuffers();
}
// Go into feedback mode and draw a rectangle around the object
#define FEED_BUFF_SIZE 4096
void MakeSelection(int nChoice)
{
// Space for the feedback buffer
GLfloat feedBackBuff[FEED_BUFF_SIZE]; // Storeage for counters, etc.
int size,i,j,count; // Initial minimum and maximum values
bRect.right = bRect.bottom = -999999.0f;
bRect.left = bRect.top =  999999.0f; // Set the feedback buffer
glFeedbackBuffer(FEED_BUFF_SIZE,GL_2D, feedBackBuff); // Enter feedback mode
glRenderMode(GL_FEEDBACK); // Redraw the scene
DrawObjects(); // Leave feedback mode
size = glRenderMode(GL_RENDER); // Parse the feedback buffer and get the
// min and max X and Y window coordinates
i = 0;
while(i < size)
{
// Search for appropriate token
if(feedBackBuff[i] == GL_PASS_THROUGH_TOKEN)
if(feedBackBuff[i+1] == (GLfloat)nChoice)
{
i+= 2;
// Loop until next token is reached
while(i < size && feedBackBuff[i] != GL_PASS_THROUGH_TOKEN)
{
// Just get the polygons
if(feedBackBuff[i] == GL_POLYGON_TOKEN)
{
// Get all the values for this polygon
count = (int)feedBackBuff[++i]; // How many vertices
i++; for(j = 0; j < count; j++) // Loop for each vertex
{
// Min and Max X
if(feedBackBuff[i] > bRect.right)
bRect.right = feedBackBuff[i]; if(feedBackBuff[i] < bRect.left)
bRect.left = feedBackBuff[i];
i++; // Min and Max Y
if(feedBackBuff[i] > bRect.bottom)
bRect.bottom = feedBackBuff[i]; if(feedBackBuff[i] < bRect.top)
bRect.top = feedBackBuff[i];
i++;
}
}
else
i++; // Get next index and keep looking
}
break;
}
i++;
}
}// Process the selection, which is triggered by a right mouse
// click at (xPos, yPos).
#define BUFFER_LENGTH 64
void ProcessSelection(int xPos, int yPos)
{
// Space for selection buffer
GLuint selectBuff[BUFFER_LENGTH]; // Hit counter and viewport storeage
GLint hits, viewport[4]; // Setup selection buffer
glSelectBuffer(BUFFER_LENGTH, selectBuff);

// Get the viewport
glGetIntegerv(GL_VIEWPORT, viewport); // Switch to projection and save the matrix
glMatrixMode(GL_PROJECTION);
glPushMatrix(); // Change render mode
glRenderMode(GL_SELECT); // Establish new clipping volume to be unit cube around
// mouse cursor point (xPos, yPos) and extending two pixels
// in the vertical and horzontal direction
glLoadIdentity();
gluPickMatrix(xPos, viewport[3] - yPos, 2,2, viewport); // Apply perspective matrix
gluPerspective(60.0f, fAspect, 1.0, 425.0); // Draw the scene
DrawObjects(); // Collect the hits
hits = glRenderMode(GL_RENDER); // Restore the projection matrix
glMatrixMode(GL_PROJECTION);
glPopMatrix(); // Go back to modelview for normal rendering
glMatrixMode(GL_MODELVIEW); // If a single hit occured, display the info.
if(hits == 1)
{
MakeSelection(selectBuff[3]);
if(nWho == selectBuff[3])
nWho = 0;
else
nWho = selectBuff[3];
} glutPostRedisplay();
}
// This function does any needed initialization on the rendering
// context.  Here it sets up and initializes the lighting for
// the scene.
void SetupRC()
{
// Light values and coordinates
glEnable(GL_DEPTH_TEST); // Hidden surface removal
glFrontFace(GL_CCW); // Counter clock-wise polygons face out
//glEnable(GL_CULL_FACE); // Do not calculate insides // Enable lighting
glEnable(GL_LIGHTING); // Setup and enable light 0
glLightModelfv(GL_LIGHT_MODEL_AMBIENT,whiteLight);
glLightfv(GL_LIGHT0,GL_DIFFUSE,sourceLight);
glLightfv(GL_LIGHT0,GL_POSITION,lightPos);
glEnable(GL_LIGHT0); // Enable color tracking
glEnable(GL_COLOR_MATERIAL);

// Set Material properties to follow glColor values
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE); // Black blue background
glClearColor(0.60f, 0.60f, 0.60f, 1.0f );
glLineWidth(2.0f);
}
void ChangeSize(int w, int h)
{
// Prevent a divide by zero
if(h == 0)
h = 1; // Set Viewport to window dimensions
    glViewport(0, 0, w, h); // Calculate aspect ratio of the window
fAspect = (GLfloat)w/(GLfloat)h; // Set the perspective coordinate system
glMatrixMode(GL_PROJECTION);
glLoadIdentity(); // Field of view of 45 degrees, near and far planes 1.0 and 425
gluPerspective(60.0f, fAspect, 1.0, 425.0); // Modelview matrix reset
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}// Process the mouse click
void MouseCallback(int button, int state, int x, int y)
{
if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
ProcessSelection(x, y);
}int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutCreateWindow("Select an Object");
glutReshapeFunc(ChangeSize);
glutMouseFunc(MouseCallback);
glutDisplayFunc(RenderScene);
SetupRC();
glutMainLoop(); return 0;
}

// Planets.c
// OpenGL SuperBible, Chapter 14
// Demonstrates OpenGL Selection/Picking
// Program by Richard S. Wright Jr.#include <windows.h>
#include <gl/gl.h>
#include <gl/glu.h>
#include <gl/glut.h>
#include <math.h>
#define glRGB(x, y, z) glColor3ub((GLubyte)x, (GLubyte)y, (GLubyte)z)#define SUN 1
#define MERCURY 2
#define VENUS 3
#define EARTH 4
#define MARS 5GLfloat fAspect;// Lighting values
GLfloat  whiteLight[] = { 0.35f, 0.35f, 0.35f, 1.0f };
GLfloat  sourceLight[] = { 0.65f, 0.65f, 0.65f, 1.0f };
GLfloat lightPos[] = { 0.0f, 0.0f, 0.0f, 1.0f };
// Called to draw scene
void RenderScene(void)
{
// Clear the window with current clearing color
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Save the matrix state and do the rotations
glMatrixMode(GL_MODELVIEW);
glPushMatrix(); // Translate the whole scene out and into view
glTranslatef(0.0f, 0.0f, -300.0f); // Initialize the names stack
glInitNames();
glPushName(0);
// Set material color, Yellow
// Sun
glRGB(255, 255, 0);
glLoadName(SUN);
glutSolidSphere(15.0f, 15, 15); // Draw Mercury
glRGB(128,0,0);
glPushMatrix();
glTranslatef(24.0f, 0.0f, 0.0f);
glLoadName(MERCURY);
glutSolidSphere(2.0f,15,15);
glPopMatrix(); // Draw Venus
glPushMatrix();
glRGB(128,128,255);
glTranslatef(60.0f, 0.0f, 0.0f);
glLoadName(VENUS);
glutSolidSphere(4.0f,15,15);
glPopMatrix(); // Draw the Earth
glPushMatrix();
glRGB(0,0,255);
glTranslatef(100.0f,0.0f,0.0f);
glLoadName(EARTH);
glutSolidSphere(8.0f,15,15);
glPopMatrix(); // Draw Mars
glRGB(255,0,0);
glPushMatrix();
glTranslatef(150.0f, 0.0f, 0.0f);
glLoadName(MARS);
glutSolidSphere(4.0f,15,15);
glPopMatrix();
// Restore the matrix state
glPopMatrix(); // Modelview matrix glutSwapBuffers();
}
// Present the information on which planet/sun was selected and displayed
void ProcessPlanet(GLuint id)
{
switch(id)
{
case SUN:
MessageBox(NULL,"You clicked on the Sun!","Info",MB_OK | MB_ICONEXCLAMATION);
break; case MERCURY:
MessageBox(NULL,"You clicked on Mercury!","Info",MB_OK | MB_ICONEXCLAMATION);
break; case VENUS:
MessageBox(NULL,"You clicked on Venus!","Info",MB_OK | MB_ICONEXCLAMATION);
break; case EARTH:
MessageBox(NULL,"You clicked on Earth!","Info",MB_OK | MB_ICONEXCLAMATION);
break; case MARS:
MessageBox(NULL,"You clicked on Mars!","Info",MB_OK | MB_ICONEXCLAMATION);
break; default:
MessageBox(NULL,"Nothing was clicked on!","Error",MB_OK | MB_ICONEXCLAMATION);
break;
}
}// Process the selection, which is triggered by a right mouse
// click at (xPos, yPos).
#define BUFFER_LENGTH 64
void ProcessSelection(int xPos, int yPos)
{
// Space for selection buffer
GLuint selectBuff[BUFFER_LENGTH]; // Hit counter and viewport storeage
GLint hits, viewport[4]; // Setup selection buffer
glSelectBuffer(BUFFER_LENGTH, selectBuff);

// Get the viewport
glGetIntegerv(GL_VIEWPORT, viewport); // Switch to projection and save the matrix
glMatrixMode(GL_PROJECTION);
glPushMatrix(); // Change render mode
glRenderMode(GL_SELECT); // Establish new clipping volume to be unit cube around
// mouse cursor point (xPos, yPos) and extending two pixels
// in the vertical and horzontal direction
glLoadIdentity();
gluPickMatrix(xPos, viewport[3] - yPos, 2,2, viewport); // Apply perspective matrix
gluPerspective(45.0f, fAspect, 1.0, 425.0); // Draw the scene
RenderScene(); // Collect the hits
hits = glRenderMode(GL_RENDER); // If a single hit occured, display the info.
if(hits == 1)
ProcessPlanet(selectBuff[3]); // Restore the projection matrix
glMatrixMode(GL_PROJECTION);
glPopMatrix(); // Go back to modelview for normal rendering
glMatrixMode(GL_MODELVIEW);
}// Process the mouse click
void MouseCallback(int button, int state, int x, int y)
{
if(button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
ProcessSelection(x, y);
}
// This function does any needed initialization on the rendering
// context.
void SetupRC()
{
// Light values and coordinates
glEnable(GL_DEPTH_TEST); // Hidden surface removal
glFrontFace(GL_CCW); // Counter clock-wise polygons face out
glEnable(GL_CULL_FACE); // Do not calculate insides // Enable lighting
glEnable(GL_LIGHTING); // Setup and enable light 0
glLightModelfv(GL_LIGHT_MODEL_AMBIENT,whiteLight);
glLightfv(GL_LIGHT0,GL_DIFFUSE,sourceLight);
glLightfv(GL_LIGHT0,GL_POSITION,lightPos);
glEnable(GL_LIGHT0); // Enable color tracking
glEnable(GL_COLOR_MATERIAL);

// Set Material properties to follow glColor values
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE); // Black blue background
glClearColor(0.60f, 0.60f, 0.60f, 1.0f );
}void ChangeSize(int w, int h)
{
// Prevent a divide by zero
if(h == 0)
h = 1; // Set Viewport to window dimensions
    glViewport(0, 0, w, h); // Calculate aspect ratio of the window
fAspect = (GLfloat)w/(GLfloat)h; // Set the perspective coordinate system
glMatrixMode(GL_PROJECTION);
glLoadIdentity(); // Field of view of 45 degrees, near and far planes 1.0 and 425
gluPerspective(45.0f, fAspect, 1.0, 425.0); // Modelview matrix reset
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}int main(int argc, char* argv[])
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(600,300);
glutCreateWindow("Pick a Planet");
glutReshapeFunc(ChangeSize);
glutMouseFunc(MouseCallback);
glutDisplayFunc(RenderScene);
SetupRC();
glutMainLoop(); return 0;
}

这都是书上的例子，我要画的节点很多，每个节点都需要#define一个ID 吗？是否做个循环，每画一条连线就把两个端点的ID传给glLoadName。glSelectBuffer这个函数的参数是放节点的数组吗？

opengl反馈模式返回的是图元信息，点、线、面和多边形都是图元，看你如何设计就行。

楼主你的问题解决了吗？我现在也需要解决类似的问题。用户在场景内进行漫游，当看到管道时，可以使用鼠标在屏幕上对某段管道进行选择，能够获取该段管道的三维空间坐标（x,y,z),并对这段管道进行加亮显示。从二维屏幕位置（屏幕坐标x,y,屏幕坐标的原点应该是屏幕左上角)——转换到———三维空间的位置，好像可以使用gluProject函数来进行转换。
http://community.csdn.net/Expert/topic/3401/3401390.xml?temp=9.693545E-02一起来探讨探讨。我现在正在调试syy64(太平洋) 所给代码但是没有获取需要的结果。

我的问题还没解决，不过syy64（太平洋）给的代码是选择模式，我们好象应该用反馈模式。在绘制的过程中需要装载该图元的ID（应该这样叫吧）以及该图元的信息。但是对我来说节点数不固定，如何动态DEFINE呢？

不知道我理解的对不对？
我目前获取的坐标点的三维数据差别挺大。
目前我的理解是:在OPENGL坐标系上，根据模型的位置绘制三维模型，比如说，A模型中心位置在（-10.0,-10.0,-10.0) ,B模型中心位置在在(-8.0,2.0,3.0)等，我在opengl中按照他们的具体三维位置进行绘制，显示在三维场景中。不管视点如何变化，模型在opengl中的绝对位置不会发生改变。场景漫游只是视点发生了变化。然后场景模型会根据投影矩阵投射到屏幕上。我希望在屏幕上，使用鼠标来获取三维场景在屏幕上的三维坐标。void CMouseSelView::OnLButtonUp(UINT nFlags, CPoint point)
{
        GLfloat fdepth;                      //深度信息
        GLdouble ObjectX, ObjectY, ObjectZ;  //模型的坐标 GLint iViewPort[4];                  //视口数组
GLdouble dProjMatrix[16];            //投影矩阵
GLdouble dModelMatrix[16];          //模视矩阵 glGetIntegerv(GL_VIEWPORT, iViewPort);                 //获取视口矩阵
glGetDoublev(GL_MODELVIEW_MATRIX, dModelMatrix);   //获取模视矩阵
glGetDoublev(GL_PROJECTION_MATRIX, dProjMatrix);   //获取投影矩阵

glReadPixels(point.x, iViewPort[3]-point.y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &fdepth); //获取深度信息

gluUnProject((GLdouble)point.x, (GLdouble)(iViewPort[3]-point.y), (GLdouble)fdepth, dModelMatrix, dProjMatrix, iViewPort, &ObjectX, &ObjectY, &ObjectZ);

}        以上使我使用点击鼠标左键，来获取三维坐标的函数代码，我得理解是如果我在场景中选择了A模型，ObjectX/ObjectY/ObjectZ应该返回的是前面我所述的模型的绝对坐标，也就是（-10.0,-10.0,-10.0)，当然坐标值不一定如此精确，但是应该差别不会很大。但是目前我所获取的值差别很大，不知什么缘故？

to: pan7861(风间火月) :我给你的例子中有一个是反馈模式；
to: zh_zh_y(决不放弃)：
void CMouseSelView::OnLButtonUp(UINT nFlags, CPoint point)
{
        GLfloat fdepth;                      //深度信息
        GLdouble ObjectX, ObjectY, ObjectZ;  //模型的坐标 GLint iViewPort[4];                  //视口数组
GLdouble dProjMatrix[16];            //投影矩阵
GLdouble dModelMatrix[16];          //模视矩阵        wglMakeCurrent(hdc, hrlrc);
glGetIntegerv(GL_VIEWPORT, iViewPort);                 //获取视口矩阵
glGetDoublev(GL_MODELVIEW_MATRIX, dModelMatrix);   //获取模视矩阵
glGetDoublev(GL_PROJECTION_MATRIX, dProjMatrix);   //获取投影矩阵

glReadPixels(point.x, iViewPort[3]-point.y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &fdepth); //获取深度信息

gluUnProject((GLdouble)point.x, (GLdouble)(iViewPort[3]-point.y), (GLdouble)fdepth, dModelMatrix, dProjMatrix, iViewPort, &ObjectX, &ObjectY, &ObjectZ);
wglMakeCurrent(hdc, NULL);
}只有在场景放得比较大的情况下才比较准确。

我点在有模型处，X，Y值是0，而Z值还是天文数字也不对啊

调试易

请教OPENGL捕获坐标问题！

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