Hi Graphics gurus, I'm totally new to OpenGL and I'm trying to convert mouse events into my world coordinates. I've drawn 4 lines making a rectangle on the XY plane and I'm looking at the origin with the camera. The points of the rectangle are (-5,0),(5,0),(-5,5),(5,5)... However, the corresponding translations I'm getting from gluUnProject are (-50,0),(50,0),(-50,50),(50,50). It sure looks like I just need to divide by 10 to get the correct results... Could be a coincidence, so of course I need to know what I'm doing wrong or missing. Here's my world setup code: glfwGetWindowSize( &width, &height ); // Make sure that height is non-zero to avoid division by zero height = height < 1 ? 1 : height; glViewport( 0, 0, width, height ); // Clear color and depht buffers glClearColor( 0.0f, 0.0f, 0.0f, 0.0f ); glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); // Set up projection matrix glMatrixMode( GL_PROJECTION ); // Select projection matrix glLoadIdentity(); // Start with an identity matrix gluPerspective( // Set perspective view 65.0, // Field of view = 65 degrees (double)width/(double)height, // Window aspect (square pixels) 1.0, // Near Z clipping plane 100.0 // Far Z clippling plane ); // Set up modelview matrix glMatrixMode( GL_MODELVIEW ); // Select modelview matrix glLoadIdentity(); // Start with an identity matrix gluLookAt( // Set camera position and orientation 0.0, 0.0, 10.0, // Camera position (x,y,z) 0.0, 0.0, 0.0, // View point (x,y,z) 0.0, 1.0, 0.0 // Up-vector (x,y,z) ); drawOneLine(-5,0, 5, 0); drawOneLine(-5,0, -5, 5); drawOneLine(-5,5,5,5); drawOneLine(5,5, 5,0); ... and then here's where I call gluUnProject from within my mouse moved callback: void CGLFWTestProjectDlg::MouseMoved(int x, int y) { static GLdouble modelmatrix[16]; static GLdouble projmatrix[16]; static GLint viewport[4]; glGetDoublev(GL_MODELVIEW_MATRIX, modelmatrix); glGetDoublev(GL_PROJECTION_MATRIX, projmatrix); glGetIntegerv(GL_VIEWPORT, viewport); static GLdouble x1, y1, z1, x2, y2, z2, rx, ry; gluUnProject(x,viewport[3]-y,1,modelmatrix,projmatrix,viewport,&x2,&y2,&z2); CString S; S.Format("Mouvemoved(%d,%d) --> %lf, %lf, %lf\r\n", x,y, x2,y2, z2); ATLTRACE(S); } Any ideas what I'm doing wrong? Thanks a lot for any help! Mike

in your line of code

gluUnProject(x,viewport[3]-y,1,modelmatrix,projmatrix,viewport,&x2,&y2,&z2);

your winZ value shouldnt be 1. it needs to be something between 0 & 1. 0 being your far plane and 1 being the near plane. im not sure as to why you are getting a value that large.