Assuming one has the hardware for it, are there noticeable in-game disadvantages if I turn off texture streaming in engine.ini?
For high-end systems no. Streaming is normally intended as a performance saver as it loads textures only when they are needed. Disabling it produces better texture visuals and reduces stuttering, at the expense of more HW workload. Texture Streaming Overview | Unreal Engine Documentation Cheers
I think it effectively comes down to VRAM (as that’s where the textures are being loaded into). In my experience if you have 8GB or more you’ll certainly be fine.
I have to use r.TextureStreaming=1 not 0, or I will get load stutters/quick freezes on some routes. TGV was absolutely horrible with r.TextureStreaming=0, but much better when set to 1. I have seen some side effects from having it on, though, like interior cab textures on occasion "reloading" themselves on SPG. Like they get blurry for a second, then back to normal. Does not occur with r.TextureStreaming=0. Don't know if there is some other setting I use that causes it. Not been able to nail it down yet.
If I'm not mistaken it is an On/Off command, with 1 being on (the default) and 0 being off. You can just remove it from your .ini file entirely as TextureStreaming=1 isn't actually doing anything.
When enabled the reloading effect you see is the intentional behaviour when using any texture streaming, as the low resolution ones are loaded and replaced by the high resolution later on. That´s why I never liked it. In any game that has that feature I always disable it whenever I can. It also creates stuttering as the textures need to be loaded and unloaded instead of staying at memory (which is normally faster). For most games they recommend to disable it on high-end systems, as you can take advantage on the available HW resources to get better image quality. In TSW the rendered world (the active tile) appears to be typically less than a 2km x 2km square, so it´s not really a huge environment that would require this texture improvements in nowadays computers and the textures themselves are not ultraheavy either, specially the scenery ones. Anyway they also have LODs so the quality is adjusted by distance to player to help performance. As JetWash explained it´s enabled by default game config so r.TextureStreaming=1 makes no difference. You only need to include it in the engine.ini if you want to disable it by using r.TextureStreaming=0. However you could also try using r.Streaming.FullyLoadUsedTextures=1 instead of r.TextureStreaming=0. This will keep the streaming feature active but also keep max resolution terxtures in memory only for the ones which are being used for rendering, not for the whole scene. So it´s like and intermediate step to avoid disabling the texture streaming completely and uses less memory but you will still notice the texture reloading the first time you use an object (for instance after scenario starts or when choosing your locomotive type in the menu). Cheers