Why, in the gluLookAt() function, is the Z axis reversed?
I would have thought that if I wanted my camera to be at the origin but one unit backwards in the Z axis I would do…
gluLookAt(0.0f, 0.0f, -1.0f…
But apparently that moves the camera forward in the Z axis one unit and instead, to move the camera backwards I need to do…
gluLookAt(0.0f, 0.0f, 1.0f…
Why is this?
in gluLookAt(0., 0., 1., 0., 0., 0., 0., 1., 0.)
the eye position is (0.,0.,1.), and you are looking towards (0.,0.,0.), so the view direction is negative z-direction: (0., 0., -1.)
imagine that you draw a 2d x-y-coordinate system on a piece of paper and hold it in front of your face with the y axis pointing upwards. then your eye position is at a positive z-coordinate, and you’re looking into negative z-direction. that’s what you get if you use gluLookAt with the above values.
Just adding a comment;
By default, when modelview matrix is initialized by identity matrix, you(or camera) are looking to -Z axis direction.
Therefore, moving forward is decreasing Z value, and moving backward is increasing Z value for gluLookAt().