Why are roofs calculated from the bottom?

[NickMac]

So I have been using Roof objects as roofs and as ramps/slopes. I believe this is fairly common practice.

Why on earth does vectorworks calculate everything from the bottom? We use Top of Ridge RL's, Roof Edge and Gutter RL's. Top of slope RL's and Bottom of slope RL's. Never in all of my architectural experience have I wanted to set the bottom of a sloped object to a specific level. When designing, the important features are on top of a sloped object.

 

Apparently from the VWX perspective it is intuitive to set the bottom of the slope to the Top RL minus the cosine of the slab thickness to set the Finished Level. ???

 

It would make more sense to set the top of roof RL's that correspond with the top of the slope/roof, and let the roof thickness move down rather than up. Same for the slab tool. Why would I set my slab to -250 from the finished floor level and then add thickness on top of that. If I change my floor construction it just means that I have to get all my slabs and move them up or down. Surely it would make more sense to set a slab to the finished floor level, then let the slab thickness move the bottom down in the Z axis.

Edited June 25, 2020 by NickMac
clarification

[E|FA]

We all work differently.  In my case, I usually set the top of wall height, and then place the roof on top of that.  I don’t need to be exact in terms of the top of the roof, as long as I check that I don’t exceed the height limit. 

[NickMac]

I understand that people work differently, but I don't know if vwx does.
If we all work differently, why are we locked into the one way of setting up roofs.

Also, I don't mean to be rude, but it seems as architects, the majority of us DO need to be exact.
For example, when we are setting up an project, we import a survey, which gives us many exact RL's for slabs and ridges and valleys, of both hard and soft elements. We need to model these, but surveyors don't give us slab thickness or under slab levels. They also don't give us bottom of ridge heights. or bottom of edge of gutters.

[Samuel Derenboim]

Nick I totally agree with you. I've been having similar issues. My request would be to convert an inclined plane or 3d polygon into a roof object based on its incline slope, etc... that can be derived from 3d loci or the stake tool. Would be super handy in that case.