gluUnProject not working - c++

Question

I am trying to use gluUnProject to get my mouse coordinates into world coordinates, however it seems to not be working, or I am just misunderstanding the functionality of the glUnProject function, here is the code I am working with, my matrices all check out fine and as for the -300 on the mouse x coordinate, I am using a C++ Win32 Dialog and the ScreenToClient is giving me funky results.
int appWidth = CApplication::GetInstance()->GetWidth();
int appHeight = CApplication::GetInstance()->GetHeight();
float fAspect = (float)appWidth / (float)appHeight;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0f, fAspect, 0.1f, 100000.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(m_vecCamera.x, -m_vecCamera.y, m_vecCamera.z);
GLint viewport[4];
GLdouble modelview[16];
GLdouble projection[16];
GLfloat winX, winY, winZ;
GLdouble posX, posY, posZ;
glEnable(GL_DEPTH);
//Retrieve the Model/View, Projection, and Viewport Matrices
glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
glGetDoublev( GL_PROJECTION_MATRIX, projection );
glGetIntegerv( GL_VIEWPORT, viewport );
//Retrieve the Mouse X and the flipped Mouse Y
winX = (float)pInput->msg.param1-300.0f;
winY = (float)viewport[3]-(float)pInput->msg.param2;
glReadPixels( int(winX), int(winY), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ );
gluUnProject(winX, winY, winZ, modelview, projection, viewport, &posX, &posY, &posZ);
This is however giving me coordinates relative to the center of my screen, and I am assuming is relative to my camera, I also tried implementing my own function
Vector2f MouseUnProject(int x, int y)
{
GLint viewport[4];
GLdouble modelview[16];
GLdouble projection[16];
GLfloat winX, winY, winZ;
GLdouble posX, posY, posZ;
glEnable(GL_DEPTH);
//Retrieve the Model/View, Projection, and Viewport Matrices
glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
glGetDoublev( GL_PROJECTION_MATRIX, projection );
glGetIntegerv( GL_VIEWPORT, viewport );
//Retrieve the Mouse X and the flipped Mouse Y
winX = (float)x;
winY = (float)viewport[3]-y;
glReadPixels( int(winX), int(winY), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ );
double projectionX, projectionY;
double viewX, viewY;
double worldX, worldY;
//Convert from Screen Coords to Projection Coords
projectionX = (double)winX / ((double)viewport[2]/2.0) - 1.0;
projectionY = (double)winY / ((double)viewport[3]/2.0) + 1.0;
//Convert from projection Coords to View Coords
viewX = projectionX * modelview[14];
viewY = projectionY * modelview[14];
//Convert from View Coords to World Coords
worldX = viewX + modelview[12];
worldY = viewY - modelview[13];
return Vector2f(worldX, worldY);
}
It works to a certain mount, but when moving the camera, the numbers instantly go off a bit, the conversion from projection to view coords 'seems' to be ok, and the projection coords are definitely good.
I would really prefer to use glUnProject rather then my own function, but I can't get it to work for the life of me and all of the google searches I found don't seem to answer my question. What exactly does the GL documentation mean by 'object space' perhaps my understanding of that is wrong, and if so what do I additionally have to do to get my coordinates in the right space?

Answer 1

was posted a year ago,but anyways....so you are getting coordinates relative the the screen because you made a call to gluPerspective. this call internally calls glfrustum which will generate normalized coordinates in the range {-1, 1}. However if you called glfrustum directly with your near/far values you would have got the result from gluUnproject in that range.
To get back to your map editor coordinates, simply take the result from gluUnproject and manually range convert back to your editor coordinate system, ie{-1,1} => {0, max}
To get started you should test gluUnProject by inputting (0,0), (midX, midY), (maxX, maxY) and the result from gluUnProject should be (-1, -1, depth), (0, 0, depth) and (1, 1, depth). If you setup the projection matrix using glFrustum then the above result will be returned in the near/far range.