So just for fun I started building this ridiculously complicated glass spiral staircase and catwalk. And when I went to test it, after building the cubemaps and reloading the map... I noticed this error in the console: Failed, using default cubemap 'engine/defaultcubemap' And sure enough, there was the default cubemap (you know, that sunset skybox that shows up in Hammer when you turn off shading). It's most noticeable on the Medic's saw, and on the door, which isn't supposed to be that reflective. Furthermore, I did a quick Google search for the error, and the first result was a Steam thread saying the problem was that I needed to also build in HDR. So I tried compiling the map with the HDR option checked and building both sets of cubemaps. It seems to have remedied the problem (the door is no longer super-shiny), but it's hard to tell, since the map is now so full of bloom I can't see for shit! While this map is just for fun and practice, both of these are issues that may well come up again, and I may as well ask what the hell I'm doing wrong now.