opengl坐标变换，求助，OPENGL中屏幕坐标到世界坐标的转换

GLint viewport[4];
GLdouble modelview[16];
GLdouble projection[16];
GLfloat winX, winY, winZ;
GLdouble posX, posY, posZ;

glPushMatrix();

// 变换要绘图函数里的顺序一样，否则坐标转换会产生错误
glScalef(m_srtMatrix[0], m_srtMatrix[1], m_srtMatrix[2]); // 缩放、平移、旋转变换
glRotatef(m_srtMatrix[3], 1.0f, 0.0f, 0.0f);
glRotatef(m_srtMatrix[4], 0.0f, 1.0f, 0.0f);
glRotatef(m_srtMatrix[5], 0.0f, 0.0f, 1.0f);
glTranslatef(m_srtMatrix[6], m_srtMatrix[7], m_srtMatrix[8]);

glGetIntegerv(GL_VIEWPORT, viewport); // 得到的是最后一个设置视口的参数
glGetDoublev(GL_MODELVIEW_MATRIX, modelview);
glGetDoublev(GL_PROJECTION_MATRIX, projection);

glPopMatrix();

winX = x;
winY = screenHeight - y;
glReadPixels((int)winX, (int)winY, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ);
gluUnProject(winX, winY, winZ, modelview, projection, viewport, &posX, &posY, &posZ）;