Revit and Curves (Nightmare or Misunderstood)

[Anonymous]

Hi All,

I really think forums are not the place for complaining rants, so I'll try and phrase it like question, in the hope I learn something constructive:

Why is it so hard to work with curves in Revit? In the sketch environments non of the trim/extend commands apply to curved lines. Curved walls don't have the ability to attach to the underside of a roof. The spline sketch tool isn't available to draw a wall, so I have to start making masses. I import a spline from AutoCAD and then the pick line tool doesn't work on the imported lines.

It just seems a fair bit out of sync with it's self, and in terms of sketching it seems behind even very old versions of AutoCAD.

What does everyone else think, or am I just missing something as a begginer. 🙂 (I miss Inventor!)

GavoGarmo

[L.Maas]

I think/guess it has to do with several things. Mathematics with all kind of curvy shapes becomes much more complicated. The more you would use it the bigger hit on performance.

Revit is used for creating (large) buildings. So lots of curvy shapes can 'easily' be approached by smaller pieces of straight lines or other shapes that will approach the curve (think how it would be build in real life). So yeah I can understand why they did/do not implement too much support for curvy shapes.

Comparing it to Autocad or Inventor is not really fair. Autocad is geared to 2D drawings and made for general CAD work ranging from the very small to the very big. Inventor is in general more used for smaller objects. Even there you will see an impact on performance when you start create large (curvy)assemblies. Then inventor/you will have to employ all kinds of tricks to keep the projects manageable.

So yes, I understand why Revit does what it does.

[Anonymous]

Thanks for your thoughts.

I totally agree that a package has to keep performance very much in mind, and that the amount of polys a GPU has to handle can't be too excessive. I just don't see how being able to trim a spline or have a spline detectable by the pick line tool affects this. After lots a faffy work with masses, I can get the end result anyway, so the GPU resource isn't any better of by time I've finished, I'm just more stressed.  

[RDAOU]

I have to agree somewhat with Louis but I also believe it is not just about the Mathematics, parametrization and computation complexity nor the complexity of the building which drove the industry towards the migration from CAD to BIM. You also have to look at it from the commercial aspect of each product.

What I mean is… today (through the past 16) there are BIM products out there more than there have ever been CAD during the last 35 years and it developed in over 5-8 years more than CAD did over 40 years. And when one compares the products out there (apple to apple and not CAD to BIM), one finds that there are some products more advanced in certain areas than other and vise-versa. On the last project I was worked on in Qatar I saw Revit, GT and Tekla all in action on the same project (due to the scale of the project and the many parties involved including client, consultants, subcontractors, sub-sub…) and what one product allowed for in terms of actions/operations and/or complex commands, another didn’t and the other way round is true but at the same time none of those products seem to be complete on its own. That’s where you find many preferring one product over the other depending on the purpose this product should serve. That’s where the complementary software come into play and sometimes in certain products to a lesser or more extent than another product.

Going back to the functionality and limitation of Spline in CAD vs Revit od BIM in general…In AutoCAD (on the upside) you can draw any curve or SP Line and manipulate it in what so ever way you desire irrespective of whether it will be later executable or not but on the downside CAD doesn’t provide you with the ability to analyze and verify that it is executable on site. I BIM it’s the other way round; if you cannot build it or you don’t consider the feasibility before you draw you simple cannot draw or maybe you could but it simply won’t add up at the end. Hence, when it comes to something which is slightly more than basic, almost all BIM products resort to the specialized complementary software (example: Dynamo/Rihno-Grasshopper/…etc) providing you at the same time with the ability to communicate back and forth with those software applications (That’s part if not the essence of Collaboration). This however doesn’t mean that Autodesk cannot improve Revit to include more functionality (considering that Revit in comparison to GT/Trimble Tekla does lack some aspects) but I personally believe Autodesk’s strategy is better (ie: another example: Although Revit does massing, which for example they could have improved, they acquired Dynamo and introduced Dynamo studio as a complementary platform instead – yes performance is better with less on the complex mathematice as Louis said and yesx2 Dynamo (or even Rihno/GH) does it better and can do more so why complicate Revit…A strategy which Autodesk competitors also followed to a limited extent but one can see that they are moving more in that direction…at least my personal feeling when I look at the increasing collaboration between GT/Tekla/Trimble well and Sketchup as well.

So in a way one can’t TAG any BIM platform with the title of “Jack of all Trades” 

That was lengthy 🙂 hope you didn't read it all