Reference system symbol


I try to draw a small symbol in 3D, that represents the system of reference in a technical drawing. The above mentioned symbol must not change size when a zoom is realized. But it must rotate when the point of view of the drawing changes. Excluding the zoom, the symbol must behave like other objects of the drawing.

My problem is to exclude to the above mentioned symbol of the zoom.

Does anybody can help me? Any information in the matter will be useful for me.


One shot at it would be to use glScalef.
I suppose when you zoom you have a zoom factor or something like that. Then you could multiply or divide a glScalef before drawing your object like this:

glScalef(1.0 / zoomFactor, 1.0 / zoomFactor, 1.0 / zoomFactor);

In essence what I mean is:
when you zoom in, make the object smaller
when you zoom out, make the object bigger.
Like that you can keep a constant size.