So I implemented the fixed function version of depth cueing. I have a plan to better emulate the effect of the color maps when running in hardware, but it turns out it's a little too expensive for fixed function (i.e. 3 textures on every surface). Given the point of fixed function, I decided it'd be better to use the built in fog hardware and save the improved color map support for cards that support shaders.
The vast majority of people will have GPU's that support at least basic shaders (SM 1.1+), so the lighting and depth cueing will look better for most people. But first I'm going to get the fixed function render, which I've been showing so far, complete before worrying about putting shader support back in.
You can see the fixed-function depth cueing here:
And before (since the effect is subtle in this spot):
Another screenshot for fun:
All the basic rendering elements are in place, so the next step is to go through and fix bugs - such as occasional alignment issues with floors and walls. Once the rendering is robust I'll get the other projects rendering everything again - which should go much quicker since most of the engine work is done.
Finally once all the projects are properly rendering using the fixed function path, I'll add the shader path back in - with improved lighting and color map support - and then move on to getting the gameplay ready for the release.