color interpolation and depth cueing?

[Paul Martz]

I have a program which draws several lines, color interpolating
between vertices, which works just fine. But then I decided to add
depth cueing to the program, with these function calls:

		depthcue (TRUE);
		glcompat (GLC_ZRANGEMAP, 1);
		lsetdepth (0, 0x7fffff);
		lRGBrange (0, 0, 0, 255, 255, 255, 0, 0x7fffff);

and now it depth cues, but suddenly, the color interpolation has
stopped working altogether. As a matter of fact, ALL color in the
lines is gone, and they are instead rendered as shades of grey. This
is not what I'd expect to happen in depth cue mode. A red line which
is depth cued should just be a darker shade of red, right? Yet now
that I have depth cueing enabled, the fact that I've set different
colors on each vertex seems to be completely ignored.

What have I done wrong here? Surely it's possible to do this. Any help
is appreciated. (ps -- using a Personal Iris GT, system 3.3.1)
-- 

   -paul	pmartz at dsd.es.com
		Evans & Sutherland