OpenGL 获取当前屏幕坐标的三维坐标（gluUnProject使用例子）

本例子参考于网络，并进行了一些修改，使用glut+vs2008来实现。

在鼠标点击处重新画一个旋转的红色立方体！

参考代码如下：

    C++ Code  
 

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#include <GL/glut.h>
#include <GL/glu.h>
#include <GL/gl.h>
#include <vector>

using namespace std;

#define HEIGHT 480
#define WIDTH 640

typedef struct Point3D
{
     double objx;
     double objy;
     double objz;
}POINT_3D, *PPOINT_3D;

double objx = 0 , objy = 0 , objz = 0 ;
double objnx = 0 , objny = 0 , objnz = 0 ;
double objfx = 0 , objfy = 0 , objfz = 0 ;
double angle = 0 . 0 ;
vector<POINT_3D> vec3dPoint;
vector<POINT_3D>::iterator it;

#pragma comment(linker, "/subsystem:\" windows\ " /entry:\" mainCRTStartup\ "" )

/*THE FUNCTION TO DRAW THE STUFF ON THE SCREEN*/
void display( )
{
    glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT );

     //The big green floor like polygon
    glBegin( GL_POLYGON );
    glColor3f( 0 , 1 , 0 );
    glVertex3f( - 100 , 0 ,   100   );
    glVertex3f( - 100 , 0 , - 100   );
    glVertex3f( 100 ,   0 , - 100 );
    glVertex3f( 100 ,   0 , 100 );
    glEnd( );

     for (it = vec3dPoint.begin(); it != vec3dPoint.end(); it++)
    {
         //The red cube to be drawn at clicked position
        glPushMatrix( );
        glColor3f( 1 , 0 , 0 );
        glTranslatef( it->objx,it->objy,it->objz );
        glRotatef(angle, 1 . 0 , 1 . 0 , 1 . 0 );
        angle++;
         if (angle > 360 )
        {
            angle = 0 . 0 ;
        }
        glutSolidCube( 10 );
        glPopMatrix( );
    }

    glFlush( );
    glutSwapBuffers( );
}

void mouse( int button, int state, int x, int y)
{
     double modelview[ 16 ], projection[ 16 ];
     int viewport[ 4 ];
     float z = 1 ;

     /*Read the projection, modelview and viewport matrices
    using the glGet functions.*/
    glGetDoublev( GL_PROJECTION_MATRIX, projection );
    glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
    glGetIntegerv( GL_VIEWPORT, viewport );

     //Read the window z value from the z-buffer
    glReadPixels( x, viewport[ 3 ]-y, 1 , 1 , GL_DEPTH_COMPONENT, GL_FLOAT, &z );

     //Use the gluUnProject to get the world co-ordinates of
     //the point the user clicked and save in objx, objy, objz.
    gluUnProject( x, viewport[ 3 ]-y, 0.0 , modelview, projection, viewport, &objnx, &objny, &objnz );
    gluUnProject( x, viewport[ 3 ]-y, z, modelview, projection, viewport, &objx, &objy, &objz );
    gluUnProject( x, viewport[ 3 ]-y, 1 . 0 , modelview, projection, viewport, &objfx, &objfy, &objfz );
    POINT_3D objxyz;
    objxyz.objx = objx;
    objxyz.objy = objy;
    objxyz.objz = objz;
    vec3dPoint.push_back(objxyz);
}

void initVector()
{
    vec3dPoint.clear();
    POINT_3D objxyz;
    objxyz.objx = objx;
    objxyz.objy = objy;
    objxyz.objz = objz;
    vec3dPoint.push_back(objxyz);
}

void init( int width, int height )
{
    glViewport( 0 , 0 , width, height );
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity( );
    gluPerspective( 45 , 1 . 33 , 0 . 1 , 400 );
    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity( );
    gluLookAt( 0 , 100 , 200 , 0 , 0 , 0 , 0 , 1 , 0 );
}

int main( int argc, char **argv )
{
    glutInit( &argc, argv );
     //The most important part specify the things your
     //glut window should provide
    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
    glutInitWindowSize( 640 , 480 );
    glutCreateWindow( "gluUnProject Demo" );

    glClearColor( 0 , 0 , 0 , 0 );
     //enable z buffer
    glEnable( GL_DEPTH_TEST );
     //set the value in z-buffer as 1.0
    glClearDepth( 1 . 0 );
    initVector();
    init( 640 , 480 );
    glutDisplayFunc( display );
    glutReshapeFunc( init );
    glutIdleFunc( display );
    glutMouseFunc( mouse );
    glutMainLoop( );
}

OpenGL 获取当前屏幕坐标的三维坐标（gluUnProject使用例子）

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