This isn't exactly a "bug", since this never has been included in the previous games, but the cab displays should emit a bit of light. For example, with the BR 401, when entering a tunnel in real life, the cab doesn't go completely dark, because the various gauges and mostly the displays shine a bit of light on everything. It isn't much, but enough to see the switches in front of you (you can see this on in-cab videos of the BR 401). The same applies for other trains with cab displays. If the displays acted as weak, blue-ish light sources, this would enhance the realism and immersion, and also make it easier (or rather possible) to see your controls in tunnels and at night. I had hoped this would have been implemented with the new lighting system, but it hasn't. Please consider adding light emitting displays.
Actually these displays do emit light in TSW3. But it's not enough to lit up the environment. If we would crank that up to lit up the cab, you would lose the ability to read them as they get a little sun. A limitation of the emissive light sources i think. Yes, there could be placed extra point lights to give the immersion, but each extra light costs performance, and there would be a buch of extra lights needed just to give that effect.
I think the extra point lights wouldn't cost too much performance. It doesn't need to be perfect, a single point light for each display would suffice. In the case of the BR 401, that's 4 point lights. I am sure this would suffice because even the desk light, which isn't centered on the dsiplay of course, looks to me like it could work to emulate the middle display if it were dimmed and blue. Sure, 4 extra point lights is more than 0 extra point lights, but I think the cab light is also at least two point lights (correct me if I'm wrong) and it has a negligible performance impact as far as I can tell.
Actually a rectangle light source used there I wouldn't use it for the displays at all. The problem here is the amount of overlapping light sources. The display lights would be always on. At a minimum two of them would overlap. That is ok so far. But with the MFD and the cab lights on we would have 4 light sources overlapping. That is a problem for sure. Not sure how much on PC, but definitely on consoles. Would need profiling to get the precise idea of how much it has an impact.
