View Full Version : yet another gluUnProject question...

12-11-2002, 01:31 PM
Hi all, I've searched the forums and looked at the Red Book example but still can't figure out what is going wrong with my program so I thought I make yet another post about gluUnProject(), which i guess can be tricky to use...

Here's what I'm trying to do: I would like to drag points in 3d world but the z-value is fixed (so i guess i won't need glreadpixel). but of course it didn't work. the unprojected values only change by super small fractions! however, it seems that if I scale up the mouse positions by like 1000 then I get some movements, so could it be that I'm not taking into account the camera orientations? (I need to zoom out quite a bit.) The code is as follows:

GLdouble model[16], proj[16];
GLint view[4];

double wx, wy, wz;

glGetDoublev(GL_PROJECTION_MATRIX, proj);
glGetDoublev(GL_MODELVIEW_MATRIX, model);
glGetIntegerv(GL_VIEWPORT, view);

cerr << "mouse pos: " << m_lastMouseX << " " << (h() - m_lastMouseY) << endl;

gluUnProject((double)m_lastMouseX, (double)(h() - m_lastMouseY), 0, model, proj, view, &wx, &wy, &wz);

cerr << "unprojected to: " << "(" << wx << ", " << wy << ")\n";

Markers.pos[0] = wx;
Markers.pos[1] = wy;
Markers.pos[2] = *some fixed value*

I printed out the view and projection matrices:

1 0 0 0
0 0.999994 -0.00333332 0
0 0.00333332 0.999994 0
-14.1621 -8.28815 -39.5964 1

3.73205 0 0 0
0 3.73205 0 0
0 0 -1 -1
0 0 -0.02 0

and they agree with the ones i used for drawing... Anyway anybody got some ideas or perhaps alternatives to dragging points on screen?

any help would be greatly appreciated as i'm getting increasingly frustrated by this bug...

12-11-2002, 02:07 PM
I don't really understand what you want to do but have you tried searching this forum for "gluUnProject" ?
There's been a few discussions about all this around here before.


(Searching on "gluUnProject" gave me 82 topics)

[This message has been edited by fritzlang (edited 12-11-2002).]