Hi Alex,
Thanks for the feedback.
The reason we made this change is the following:
When you go into manual support mode, it’s not clear exactly what height the model will be at once the supports are generated, for the following reasons:
- It is possible to end up with a support structure with only internal supports. In this case the model would be sitting on the build platform, and therefore at a different height than it would be at if there were a support raft.
- Because of precision issues that are always present in computational geometry applications, even with the assumption that there will indeed be a support raft (which is almost always the case), the exact height at which the model will be is hard to predict.
Our fear was that customers would rely on the slice tool in manual support mode to find unsupported minimas. Of course that is a very convenient way to use the tool, and we didn’t realize just how many people were already using it that way. The concern was that customers would think that all of their minimas are supported because the manual support slicer does not show any unsupported minimas – but because the slices are not necessarily at exactly the right height, this conclusion would be incorrect, and could result in confusing print failures.
In practice, the slice tool in manual support mode already worked well for the purpose of finding unsupported minimas, despite the issues I mentioned above, so in retrospect it was probably a mistake to change it to behave as it currently does.
Our plan for a future version of PreForm is to have the slice tool work in manual support mode nearly the same way that it works in the “normal” mode, with the assumption that once supports are generated, there will indeed be a support raft. This is roughly how it worked before, and people seemed to have a good interaction with it.
You also mentioned that you would like an option to have the slice tool stay at the same height when toggling between manual support mode and “normal” mode. The reason that we reset the slice tool when switching between these modes is the following: if you are in “normal” mode and inspecting a slice near the top of the model, then most of the model is visible (because only a small portion is cut off). If you switch to manual support mode, the slice inspection switches from cutting off the top of the model to cutting off the bottom. (We inspect the model from the bottom in manual support mode so that people can reach difficult-to-see areas of their models to edit internal supports.) This results in an extremely confusing interaction where the model seems to completely disappear when you enter manual support mode if you were inspecting a slice near the top of the model.
Having the ability to toggle between the “resetting” behavior and a “remember my slice” behavior is an option, but we try hard to keep the PreForm interface as un-cluttered as possible, so it is something we would have to explore from a user interaction perspective, and is not currently in the plans.
Thanks again for the feedback and sorry for the trouble this has caused you,
Andrey