From reading, and taking literally, that an illusion cannot generate light.Where does the stuff about reflections come from?
Having the illusion cast a reflection means it's generating light. In particular, consider a situation where an observer can see the illusion but not the light source (maybe the light's around a corner, or the viewer is indoors but the illusion is outside "reflecting" the sun).
My point exactly. Not allowing illusions to generate light ends up being a huge nerf.An illusion can't create light (unless specified), but it does presumably respond to ambient lighting levels (i.e. an image cast in a completely dark room is invisible, but if you shine a light upon it, it will be revealed, and will appear to be being lit from that direction). That pretty much has to be the case for it to work at all and not be immediately obvious as an illusion.
Easy enough to rule that an illusion cannot generate light beyond what the surrounding environment is already providing - this allows for reflections but prevents it being used as a Light spell. Still doesn't answer my glowing-sword example, though, as to me that's something I feel I should be able to do - have the glow, even if it's limited to dim, be visible even if the room is otherwise dark in order to attract attention.
If the illusionist could see both the reflecting surface and the viewer, and have it react properly (check definitely required!), I'd allow an illusion to function as a mirror. But if the caster couldn't see one or the other the mirror effect wouldn't be possible.So, if the object can appear to be lit differently depending upon the ambient light (i.e. it has the appearance of reflecting that light), and if you can see different parts of it as you walk around it, at what point does a reflective surface become too reflective to work that way?