How do I use gluLookAt properly?

Question

I don\'t want to get into complex trigonometry to calculate rotations and things like that for my 3D world so gluLookAt seems like a nice alternative. According to the docum

Answer 1

(The intuition behind the "up" vector in gluLookAt is simple: Look at anything. Now tilt your head 90 degrees. Where you are hasn't changed, the direction you're looking at hasn't changed, but the image in your retina clearly has. What's the difference? Where the top of your head is pointing to. That's the up vector.)

But to answer your question: gluLookAt calls should not be concatenated. In other words, the only pattern in which it's OK to use gluLookAt if you don't know exactly how it works is the following:

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(...);
# do not touch the modelview matrix anymore!

It seems from your code that you're doing something like this:

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(...);
# some stuff..
gluLookAt(...);

This will generate weird results, because gluLookAt multiplies the current matrix by the viewing matrix it computes. If you want to concatenate transformations you're really better off figuring out how to make glTranslate, glScale and glRotatef work for you. Even better, you should learn how the coordinate transformations work and stick to glMultMatrix.