I get really strange values when I do my projection with gluUnProject.
One is supposed to put the screen coordinates as in-parameter to gluUnProject. Is it so easy that I can take the x/y values from the mouseevent I receive with a mouse click and use them as screen coordinates, what do I do with the z-coordinate?? I´ve read that one should use glReadPixels. But I don´t manage that…
some code:
GLdouble modelviewMatrix[16];
GLdouble projectionMatrix[16];
GLint viewport[4];
GLdouble winx,winy,winz;
GLdouble objx, objy, objz;
GLvoid* depth = 0; // is this right???
int x,y;
float z;
z = 0;
event.GetPosition(&x,&y);
winx = (GLdouble) x;
winy = (GLdouble) 250-y; // window height - y
// get the z-value
glReadPixels(x,y,1,1,GL_DEPTH_COMPONENT,GL_FLOAT,depth);
//z = (float) *depth; // right???
winz = (GLdouble) z;
// here we should get the object coordinates from the screen coordinates
glMatrixMode(GL_MODELVIEW);
glGetDoublev(GL_MODELVIEW_MATRIX, modelviewMatrix);
glMatrixMode(GL_PROJECTION);
glGetDoublev(GL_PROJECTION_MATRIX , projectionMatrix);
glGetIntegerv(GL_VIEWPORT,viewport);
gluUnProject(winx,winy,winz,modelviewMatrix,projectionMatrix,viewport,&objx,&objy,&objz);
// the object coordinates are now stored in objx/y/z
/grodslukaren