I've just done my first 3D model in 2020, and it involved around 100 solid subtract actions.
(It's a crane tower made from steel pipe, and each piece of pipe needs to be trimmed to fit so I can accurately calculate mass)
I'm happy to report that I didn't get any of the 'The resulting solid won't be watertight, do you want to continue' messages so it generally seems to work better. 90% of the resulting solids were able to return volumes but on those that didn't I decided to run the 'watertight' and the new 'leak' tests.
I checked the help file for both (although we still can't 'search' the help files) & the info is in the folder:
Creating 3D Objects/3D Solid Editing Operations/
(even though neither command will edit anything)
For some reason the 'Watertight' command can be found in:
While the 'Leak Test' can be found in:
IMHO both commands should be in the 'Tools' menu - as I said, they don't edit anything - they both really perform the same function except the leak test does make an attempt at finding the problem .
Here's what happened for me.
The watertight test confirmed 'Yup, all good' or 'Nah, bollocks' when run (which I kind-of knew anyway because the broken solids can't calculate volumes.)
The Leak test failed on every solid with the response 'The selected object is not a solid surface entity'.
There is no info anywhere in the help files on 'solid surfaces' but I do recall some discussions about it a few years back, so I went in search on the forum and found a post in 2015 by DT:
There are three ways to create a Solid Surface object in DesignCAD 3D Max 25:
1) With the "Use surface representation" option checked in General Options, do any kind of Boolean operation on two solids.
2) With "Use surface representation" unchecked, but with one or more existing Solid Surface objects in the drawing, do a Boolean between a regular solid and a Solid Surface. The result of a mixture of solids and Solid Surfaces will always be a Solid Surface.
3) Select a regular solid, and use Edit/Selection Edit/Convert/Solid To Surface.
Now, I remember people having issues with solid Surface back then so I gave it a wide berth and continued with what I know works, but it begs the questions:
If Solid Surfaces are better, why is there no info on it anywhere, and why do we still have to chose it instead of simply changing the program to use it by default?
If Solid Surfaces are worse, why are they there as an option at all?
If they are better at some things but worse at others, why isn't there any explanation that's easy to find so we know when to change from one to the other?
I finally converted one of my errant solids to a solid surface and ran the leak test successfully. It did work, but it's an extraordinarily clumsy tool to use.
When I ran it the screen flickered rapidly for a second then stopped without any report screen popup to give results.
Because I'd found the help topic I knew it was supposed to create 2 layers, but it was up to me to go and hunt for them.
(For me they were layers 27 & 33 - probably the first vacant layers in my list)
The edit on the new layer was hard to find - i just had one hole edge traced in red, but because my solid is orange I couldn't see it. I had to find the layer, disable multi-layer editing and select the whole object in point-select to find it.
Like I said, it works but it's clumsy.