Cutout/clip needs treshold spinner as well.
No it doesn't. Its entire point is that there can be only white or black. That's where the performance optimization comes from. It's used strictly to prevent any kind of semi-transparency in your material, so you get a nice rays/s boost on things like opacity mapped tree leaves. Any kind of threshold introduction would immediately disable the effect. Non the less, you can always just do it yourself using an output curve. No need to clutter UI with something so incredibly specific.
Maybe i used wrong terminology, perhaps it should be called bias or something similar. Basically what i mean, it needs controls to shift clamp line from 128, 128, 128 to either direction. Of course it could be done with additional output node, but then again, clamping itself can be achieved with output, so why bother in the first place?
Average users do not know what is benefit of clipping opacity maps, they do not even know why clipping will make opacity faster. They will just have a checkbox which they know if they turn on, will speed up their rendering, but makes leaves noisier in case of animation. So even noobs can then apply it, by using following reasoning: "Is this material for example tree leaves? Yes? Will I animate the scene? No? Great, I can turn this on and speed up my render!"
I can't think of any reason where you would want to shift clamp line in terms of
optimization. Most of the average leaf opacity maps will look nearly the same no matter where you shift the clamp line. This is not for artistic control, if you need to shift clamping level for some artistic effect, then either mix map mix curve, or output rollout are your place to go. In material itself, this is as an optimization tool, not as an artistic control tool. Obviously, you won't be using it opacity maps that have large gradients in them.
Right now, if an user sees clamp, and is explained that enabling it in non animated scenes can give speed boost, then it's really easy to understand. But if you see a checkbox that enables some threshold value, which then gives very complex explanation about what's happening inside and how the threshold affects it, it may imply to new users that it's not just click->speedup solution, but that you need to somehow tweak that optimization using this value to get ideal results. That could put many people off and simply make them ignore the thing ;)
Another thing is that they could easily misunderstand and misinterpret the explanation, and that could in turn increase room for error. For example, one could think "I want to optimize ALL of my map, entire range, so I will set threshold all the way to 1" Efficiently making opacity opaque, and turning leaves into poly squares. Or other way around.
It's really easy to request things that suit your worfklow... but I personally always cross-check them with "How would this appear to a person that is completely new to 3D rendering".
