Documentations say that, glDepthRange defines the mapping of normalized device coordinates (range [-1, 1]) with the window-space Z coordinate ranges from [0, 1]. -1 is mapped to near values and 1 in mapped to far value.

But, what exactly is the use of this ? if I give glDepthRange(0.4,0.6), will it cause clipping of the graphics ? (I tried this but did not see any impact). Also, how is it different from the last two parameters of glOrtho function ?