I am listing here a bunch of issues that I encountered during recent lengthy sessions with Simplify3D's "add support" feature. I am posting here to invite any additional related comments users might have.
This is is for version 4.1.2, the latest version.
1. Mouse-controlled rotation issues:
a. Center of rotation of view: During addition of supports, it's necessary to frequently rotate the view to see different angles of the bottom surface to which you are trying to add supports. This while zoomed in quite close. Unfortunately, rotation is around the middle of the build volume, which might be 100-200mm above the part bottom, making the rotations very unwieldy. Instead, rotation should be around a point much closer to the middle of the body, or even the middle of the bottom of the part. Possibly a dynamically selectable center of rotation.
A partial workaround: Use Tools > Options > Machine to temporarily set the build volume to say 10mm or 20mm high. This fools S3D into rotating round a much better point.
b. Wrong-way view rotation: When viewed from the bottom, Z rotation is reverse direction compared to mouse gesture, when the mouse is in the bottom half of the screen.
c. Bug: View walks off screen. Especially when zoomed in, press-drag an extended single sequence of rotations causes the view to "walk" in some direction to off screen, so that the view has to be dragged back on screen. In some cases the view walks in the direction of the "camera", first partially and then fully disappearing, which must be recovered via View > Default. To be clear -- this is all for a single continuous mouse drag gesture, not multiple moves. So conceptually, such a gesture should always include the possibility of returning to the view position at the start of the gesture. But here it does not.
This is the sort of error that occurs if every incremental view position change (as the mouse moves) is based on the previous incremental view position -- a long sequence of these accumulates errors. (Instead, the code should accumulate the incremental changes in mouse movement, and apply the cumulative total to the original position of the view before the mouse press.)
2. Adding/deleting supports
a. Never add support while positioning the view! When press-dragging the view, S3D should not interpret this as a command to add a support. Sometimes S3D handles this correctly, at other times it gets into a mode where it consistently adds a support as well as moving the view.
b. Implement Shift-click to delete support. Currently, while in "Add new support structure" mode, mouse-click adds a support. But to delete either an unwanted prior support, or an accidentally placed support, it's necessary to mvoe the mouse over to the dialog to select "Remove existing supports" mode. (and then the reverse when done). This is extremely tedious and annoying. It would be a very welcome if in "Add support" mode, we could just use Shift-click to delete a support.
c. Confirmation before mass deletion. Please please add a confirmation dialog for any of the Support Gen functions that are going to wipe out the painstakingly manually added supports. That includes "Generate Automatic Supports". It's waaaaay too easy to hit the wrong button when trying to deal with the current necessity to visit the dialog over and over to switch between add and delete modes. Which it's necessary to do because of the unwanted additions during using the mouse to move the view. Cascade of trouble.
d. Visualization for support column length. It would be super helpful if the UI could give some idea of support column length while placing them. As currently implemented, you can see support length vary as you move the support over the lower surface, but only while viewing from an angle. If you view the bottom surface face-on, you can't see the sides of the support, of course. So when trying to place supports under downward-pointing peaks, it can be difficult to judge where those are just based on shading.
3. View obstructed by the build-plate grid. It would be helpful to be able to turn off the grid that represents the build plate while adding supports (and thus viewing from underneath through that grid).
4. Bug in automatic support generation leaves out crucial supports.
(This one I also reported direct to the Contact page, as it's somewhat higher priority.)
The automatic Support Generation algorithm gets fooled into omitting support for downward-pointing peaks (which must be supported), when the faces adjacent to those peaks are at > 45 degrees from horizontal. The attached image shows this case.