How do artists tweak the result of procedural generation without having to just try different random seeds? Are there tools to provide feedback on generated results to optimize for what the artist wants without having to specify every detail by hand?
Usually, you can tweak the results based on what the artist is looking for. Unreal Engine 4 works on procedural material and you can see from the screen cap of the UI, that there are numerous fields the artist or game maker can tweak to their liking. https://wiki.unrealengine.com/Procedural_Materials. What's even more impressive is that UE4 is completely online, so unlike how we do renders offline, and look at the rendered still, game engines do this real time