Circular Revolve

[cheukling125525.110216]

I created a circular extrusion and intended to built a circular
revolve on top of it, so that it looks like a screw end.
However, revit cannot make my desire result, it's a polygon like structure.
What's wrong with it ?
Please can someone point out my mistake ?

Regards
Cheuk

[Jshaver]

From what I have seen this is due to Revit's inability to REGEN. (if thats the correct term) It is a limitation in the software. It is very apparent in your family due to the elements being very small. I am unaware of any native method for correcting your family..unless it is not parametric and you have autocad handy;). You may be able to import the geometry from autocad (but do not explode) and it should display correctly.

I am assuming that due to the rarity of objects this small in projects autodesk did not increase the accuracy of these types of elements to avoid hindering performance.

Any else have other suggestions?

edit: Scratch the idea of importing from autocad...It did create some even wierder geometry though...What I find interesting is when you export the family you created to autocad as an acis solid, it displays accurately and smooth in autocad. This makes me feel even more confident that the limitation is just the revit software. I am still playing around to see if a workaround is probable.

I have run into this issue on a much larger scale. i.e. long curved trusses. The geometry is never accurate as the curve is always segmented when you zoom in. This is horrible behavior when you are trying to place joists along the edge. I always have to result to exporting to autcad to get the correct distances and then update the model.

See attached for autocad/revit screenshot

[cheukling125525.110216]

100% agree with your observation.
I made another one with much more smaller in size , and found that
the polygonal becomes rectangle this time !!!
So importing from acad, relinquish parametric behaviour is the only choice.

[Steve_Stafford]

It has nothing to do with REGEN, an AutoCAD term for refreshing the screen display which in Revit is F5 or View menu > Refresh. The issue is that Revit doesn't expect you to model the threads on screws so that level of detail isn't supported as a modelling task with solids or voids. Very tiny arc segments will degenerate into straight segments as a result. Built in assumptions of purpose and intent. That is the problem with assumptions and decisions, they don't always satisfy everyone.

[Jshaver]

I think this IS an issue that autodesk will need to address. Not so much for the small elements but even on large curved trusses the geometry is distorted. The accuracy of your modeling is hindered/handicapped by this. We have a large number of projects that use long spanning curved members and it is not possible to accurately place the bar joists. I am always resulting to an autocad export to give me the proper location.
(see attached)



The error is sometimes magnified when exporting to 3rd party software, i.e. navisworks or analysis programs.
Due to an exported .dwg file displaying properly I would assume that the revit has all the content/information it needs it just does not display it properly. Would this be due to the softwares code? What has to be done from a programming standpoint to correct such an issue.