opengl屏幕坐标转换世界桌标，我的代码怎么就是结果不对
void openglwidget::unPorject(real4 screen,real4* minWorld,real4* maxWorld) {
GLint viewport[4];
GLdouble modelview[16];
GLdouble projection[16];
GLdouble posX, posY, posZ;
ViewSize viewSize;
viewSize.x = viewport[2];
viewSize.y = viewport[3];
glGetIntegerv(GL_VIEWPORT, viewport); /* 获取三个矩阵 */
glGetDoublev(GL_MODELVIEW_MATRIX, modelview);
glGetDoublev(GL_PROJECTION_MATRIX, projection);
GLfloat winX = (float)screen.x;
GLfloat winY = viewport[3] - (GLint)screen.y-1;
gluUnProject(winX, winY, 0, modelview, projection, viewport, &posX, &posY, &posZ);
minWorld->x = posX;
minWorld->y = posY;
minWorld->z = posZ;
gluUnProject(winX, winY, 1, modelview, projection, viewport, &posX, &posY, &posZ);
maxWorld->x = posX;
maxWorld->y = posY;
maxWorld->z = posZ;
}