OpenGL 获取当前屏幕坐标对应的三维坐标，使用很简单glu库中的一个函数

#include <GL/glut.h>

#include <stdlib.h>

#include <stdio.h>

void display(void)

{

glClear(GL_COLOR_BUFFER_BIT);

glFlush();

}

/* Change these values for a different transformation */

void reshape(int w, int h)

{

glViewport (0, 0, (GLsizei) w, (GLsizei) h);

glMatrixMode(GL_PROJECTION);

glLoadIdentity();

gluPerspective (45.0, (GLfloat) w/(GLfloat) h, 1.0, 100.0);

glMatrixMode(GL_MODELVIEW);

glLoadIdentity();

}

void mouse(int button, int state, int x, int y)

{

GLint viewport[4];

GLdouble mvmatrix[16], projmatrix[16];

GLint realy;  /*  OpenGL y coordinate position */

GLdouble wx, wy, wz;  /*  returned world x, y, z coords */

switch (button) {

case GLUT_LEFT_BUTTON:

if (state == GLUT_DOWN) {

glGetIntegerv (GL_VIEWPORT, viewport);

glGetDoublev (GL_MODELVIEW_MATRIX, mvmatrix);

glGetDoublev (GL_PROJECTION_MATRIX, projmatrix);

/*  note viewport[3] is height of window in pixels */

realy = viewport[3] - (GLint) y - 1;

printf ("Coordinates at cursor are (%4d, %4d)\n", x, realy);

gluUnProject ((GLdouble) x, (GLdouble) realy, 0.0,

mvmatrix, projmatrix, viewport, &wx, &wy, &wz);

printf ("World coords at z=0.0 are (%f, %f, %f)\n",

wx, wy, wz);

gluUnProject ((GLdouble) x, (GLdouble) realy, 1.0,

mvmatrix, projmatrix, viewport, &wx, &wy, &wz);

printf ("World coords at z=1.0 are (%f, %f, %f)\n",

wx, wy, wz);

}

break;

case GLUT_RIGHT_BUTTON:

if (state == GLUT_DOWN)

exit(0);

break;

default:

break;

}

}

void keyboard(unsigned char key, int x, int y)

{

switch (key) {

case 27:

exit(0);

break;

}

}

/*

*  Open window, register input callback functions

*/

int main(int argc, char** argv)

{

glutInit(&argc, argv);

glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);

glutInitWindowSize (500, 500);

glutInitWindowPosition (100, 100);

glutCreateWindow (argv[0]);

glutDisplayFunc(display);

glutReshapeFunc(reshape);

glutKeyboardFunc (keyboard);

glutMouseFunc(mouse);

glutMainLoop();

return 0;

}

//相关API含义

gluPerspective  //指定观察视景体

gluUnProject  //传入模型矩阵和视点矩阵，根据当期屏幕坐标，返回对应的三维坐标。