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Manipulating Revit gbxml files so the building geometry can be imported into a load software

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Message 1 of 31
mbeckwithUMVQ6
3436 Views, 30 Replies

Manipulating Revit gbxml files so the building geometry can be imported into a load software

I'm trying to learn how to use gbxml files from Revit 2022 to avoid inputting the space geometry into our load programs. I'm confused on how to format the text file in a way that will reduce as many errors as possible.

 

I've been using the Ladybug Spider tool to get rid of duplicate adjacent surfaces. I've also been using the gbxml online validator (https://gbxml.org/validator/Pages/TestPage.aspx) but every gbxml file that I export from Revit does not pass the validation tests. I'm also having issues when I import the data into Open Studio, i appears that some windows are being considered walls.

 

My main question is how do you export/manipulate a gbxml file in Revit properly? I've read the Autodesk guidance about the energy setting but I'm not seeing a difference with my exported models. I feel like it shouldn't be this hard and it would save our company countless hours. I really hate recreating the building from scratch in Trane Trace or HAP so I really want to figure this out.

 

I have used Revit for a long time and I fee like I know the program very well. But I'm pulling my hair out with this issue and I'm not sure why Revit is exporting a file with the wrong schema.

 

Any advice at all would be appreciated

30 REPLIES 30
Message 2 of 31
iainsavage
in reply to: mbeckwithUMVQ6

Exploring this aspect of Revit has been on my to-do list for a while but colleagues who’ve used the gbxml export have experienced similar problems to yourself I think.

If you’ve read the documentation you maybe noticed that the help says Revit uses the 0.37 schema which, according to the gbxml website, dates from 2010 and has been superseded 6 times with version 6.01 now being the current version. I’m no expert on this but I would wonder if those updates included bug fixes and improvements (why else would they change it?) so maybe the problem is Revit using an old schema.

I know that our IESVE software has their own BIM import tool and part of what it does is supposedly to “heal” issues with geometry exported from other packages which would imply that the export process is known to maybe not be perfect. Do Trane have something similar?

Although I’m usually an advocate for using Revit I have been very disappointed with the energy analysis aspect of it and simply don’t trust it. If you search the forum you’ll find others saying similar things.

Doesn’t really answer your question though.

 

Message 3 of 31
iainsavage
in reply to: iainsavage

I just noticed as well that the validation tool you provided the link to doesn’t have an option for version 0.37 so that’s probably why your failing the test.

Message 4 of 31
dyp4f
in reply to: mbeckwithUMVQ6

Since an error in gbxml schema such obvious and well known is unfortunately not fixed for several years, I am wondering if there is a utility to convert the Revit produced gbxml file from v.0.37 to the current version v.6.01.

Message 5 of 31
mbeckwithUMVQ6
in reply to: iainsavage

I missed that detail. What's the point of gbxml files if the #1 BIM software can't properly utilize it? Does no one use gbxml files?

 

Message 6 of 31
RobDraw
in reply to: mbeckwithUMVQ6

Most programs cannot always give perfect exports that will work properly with every program that uses the export format. Most need to be refined in some way. Some more than others. 

 

I've only skimmed the surface of utilizing GBXML and found the process quite complicated and the output hard to understand for a novice like me. Some of the issues had to do with the way the model was built. Unfortunately, my architectural experience is very limited and the models I was working with were from third parties and no one else in my office had ever done Revit, nevermind architectural. So I wasn't able to easily fix the issues with the models to a point that gave a good GBXML. 

 

I know it seems like I'm rambling but my point is that the issues may not only be with the inner workings of the export process but could include the model not being constructed with the export in mind. Garbage in, garbage out kind of thing. 


Rob

Drafting is a breeze and Revit doesn't always work the way you think it should.
Message 7 of 31
dyp4f
in reply to: dyp4f

Lack of (real) competition = Lack of (real) development.
That's the bitter truth about Revit...
There is not ONE (1) engineer satisfied about that situation with gbxml, but ALL pay again and again and again, every single year, for the same outdated gbxml schema (v.0.37) coming from 11 years ago !...
Message 8 of 31
RobDraw
in reply to: dyp4f

You've been drinking the wrong Kool Aid. Your editorial comments actually detract from the subject and show that you've given up hope of getting help from someone who has made it work.

 

Good luck!


Rob

Drafting is a breeze and Revit doesn't always work the way you think it should.
Message 9 of 31
dyp4f
in reply to: RobDraw

Hi RobDraw.

 

You don't really have to defend all the Revit shortcomings, unless you are an official Autodesk advocate.

If you are a Revit user, you should help the Revit community to press Autodesk for some real development.

 

Last year a group of Architect firms (large offices) sent an Open Letter to Autodesk complaining for the killing combination of:                         High Prices    AND    Lack of Development.

Do you believe that those complains are fake or invalid ?

What was the response from Autodesk ?  They added "Print to PDF" in Revit 2022 !!! ... Really ? Is that development ?

We should already have features like this one, at least 15 years ago, and instead we celebrate for the fact that we finally have that basic feature in the year 2021 !!!

 

How many billion dollars has Autodesk collected by selling annual Revit Licences since the year 2010 (when the gbxml schema 0.37 was created) until 2021 when today engineers still can't do their work ?

Do you believe that a colossal Software firm like Autodesk has any problem with finding or utilizing the right human resources or skilled programmers / developers ?

Why they don't solve the obvious problems ?

It's because they believe that users complains are not genuine ?  (just as you too seem to believe)

Or because they don't really care, since they consider that their Revit customers are practically "locked-in" ?

 

I just hope that maybe the Revit 2030 (!) will finally have an updated gbxml schema, for the then engineers to be able to finally work normally, connecting Revit with their 3-party "Heating and Cooling Loads" software !...

Message 10 of 31
RobDraw
in reply to: dyp4f

I'm not defending anything. Revit is not an end all, be all, all encompassing package. It's only a part of the BIM process. A lot of what Revit does is not meant to be much more than a convenience for analysis. Using third party software is actually recommended. This is where your Kool Aid comes in and again they are out of place here. Autodesk has other places for your thoughts if you want to gather support. This is a user help forum. Autodesk barely does anything more than administer these forums.


Rob

Drafting is a breeze and Revit doesn't always work the way you think it should.
Message 11 of 31
RIPENG
in reply to: mbeckwithUMVQ6

Ripcord Engineering uses Revit exported gbXML for nearly 100% of building analysis executed in Trane TRACE700. Hundreds of projects have been executed this way over the past five years.

 

That said, as many have found, exporting reliable gbXML from Revit takes far more 'technique' than the adverts would have you believe.

 

The guide that's probably best at explaining 'technique' is: Revit Integration with IES VE.

 

Additional guides that offer insight are: (1) DesignBuilder Revit-gbXML Tutorial and (2) EDSL Guide for Revit gbXML Files.

 

Upon review of the guides above one theme becomes clear: it is not practical to go direct from BIM background model to reliable gbXML export. There is too much modeling 'technique' involved to expect the uninitiated to nail it on their own. Frankly, there's too much 'technique' involved for the initiated to nail it in a high paced commercial environment without the use of automation.

 

To produce reliable gbXML I have found it necessary to develop abstract Building Energy Models (BEM) using BIM background provided by third parties as a basis. The workflow in 'Revit Integration with IES VE' closely describes much of the BEM development workflow Ripcord uses:

(1) Create levels,

(2) Create exterior walls,

(3) Create floors, ceiling voids, roofs,

(4) Create interior partitions,

(5) Create openings.

 

The one area where Ripcord differs from published guidance is in the use of Space Separation lines to designate all interior partitions. I have found that Space (or Room) Separation lines makes the QA/QC process much more efficient. Separation lines are an easy to see direct representation of intended boundaries between Spaces (or Rooms).

 

The problems with using Space (or Room) Separation lines as boundaries are that: (1) the Surface Type is designated as 'Air' rather than 'InteriorWall' upon gbXML export and (2) no CAD object ID is assigned to the surface. Surface Type can be corrected easily by batch editing the gbXML with the 'find and replace' utility in most text editors. Depending on the program receiving the gbXML, the effort to correct CAD object ID can be ignored.

 

Once 'technique' is ironed out it is possible to introduce automation into the mix. With model lines it is possible to designate exterior walls which Dynamo can then pick out to generate walls, floor and roofs. And there are tools available that use ray cast to automate the placement of elements like windows into walls. Ripcord has used all of the above to: (1) reduce time to develop abstract BEM and (2) increase reliability of abstract BEM & exported gbXML.

 

Exported gbXML can be good stuff. But it takes significant investment by the user to develop reliable abstract BEM to export reliable gbXML to form the basis for accurate building performance analysis workflow.

 

-Jake

Message 12 of 31
Iev60047
in reply to: RIPENG

@RIPENG That was a really informative answer. It has helped me through the past few weeks as I've struggled to develop an effective workflow for exporting a usable gbXML model from a Revit model to use in Trane's Trace 3D software analysis program. I would like to use OpenStudio, but I've found that Trace 3D has more going for it in terms of user friendliness.

 

However, I am frustrated that I cannot use space parameters (e.g. airflow, loads, lighting, people density, etc.) and building construction parameters (e.g. R-values, fenestration characteristics, etc.) for the elements from Revit to export into Trace 3D, as Trace 3D currently does not support that information from an imported gbXML. Trace 3D's official stance is that the user should use and modify building construction and the room types' templates in order to input that info. I do like the fact I can use the templates, but I think that Trace 3D should allow users to choose whether they want to use their templates or import the info from the gbXML. More flexibility in my opinion. This lack also makes it difficult to iterate load/energy models.

 

E.g. when I want to modify a wall or change the ceiling height or some other geometry related issue (generally speaking better/more refined geometry), I have to go back to Revit, re-create the geometry, delete the energy model, re-create the energy model, bring it back into a validator, re-validate and fix the serious errors/warnings, then import the fixed gbXML model back into Trace, which requires that I completely delete the old gbXML and load the new gbXML in. Then once the gbXML is loaded back in, I need to re-assign any custom loads and building construction parameters (although depending on how 'consistent' the loads and construction of the building is, the building construction and room type templates can greatly assist with this) to each room/space. This is a time-consuming process that I wish could be avoided. I.e. I wish I could use the information that I can already input into the Revit model in the Trace 3D program.

 

 Specifically, regarding the advice that space separation lines be used instead of walls, I definitely see the value in that. However, if you are fairly careful and methodical in assigning walls, floors, ceilings, roofs the appropriate exterior or interior construction type designation, you can avoid some of the more common problems. This Autodesk page is useful for figuring that out (link here). Also, splitting walls interior that are not meant to be a boundary of room is a must. Otherwise random walls will be created in the gbXML model. Then make sure to set the energy model building envelope setting to Function, to use those construction type designations for creating the energy model. That helps me create my models.

 

I am linking a picture of my personal workflow for creating usable gbXML files in Revit to use Trane Trace 3D. I know I was very specific in regards to the software that I use for load analysis, but I would prefer to be explicit on how and why I use the process I do. Hope this helps someone!

 

Revit_gbXML_Workflow.png

 

 

Message 13 of 31
HVAC-Novice
in reply to: Iev60047

Does your workflow actually work in T3D or is this just what you plan to do? I'm just asking since gbXML import is a recent T3D feature that came with an update.  Last time I used T3D, gbXML wasn't a feature. I just ended up importing a PDF (I think they added PDF tracing in addition to jpg?) of the floor plans that showed window sizes and sill heights and just traced the building from there. the way I read gbXML works now, this still may be the better way...

 

Back in T700 days the gbXML import kind of worked. But it created a lot of duplicate or 2" long walls. It required quite some manual cleanup of deleting the useless walls. The only good thing was it at least produced the windows in the correct size etc. 

 

In general T3D was/is very lacking. I hope the most recent T3D update resolves this. But I have not a lot of faith in Trane. They released a basically useless software with T3D. Many features were missing, or didn't work. It crashed, was slow etc. It took them a few years to update to a somewhat acceptable level. 

 

Many people (including myself) complain about the slow addition of features and bug resolution in Revit. But compared to Trane, Revit at least start out with a usable software. So whatever problem you may have, it could be a Trane Trace problem. 

Revit version: R2024.2.1
Message 14 of 31
Iev60047
in reply to: HVAC-Novice

@HVAC-Novice thanks for some honest feedback. Short answer: yes, I am using Trace 3D to create load reports using gbXML's from Revit. I am new (in general to HVAC, design analysis all of it) and my colleagues have told me that it's come a long way in the past 1.5 to 2 years. Yes, you can't import thermal properties and room loads from the gbXML file (which I still think would be a huge improvement) but that alone doesn't entirely prohibit a useful workflow for using Revit to create gbXML files for import. 

 

There are number of reports you are offered to create, so just as a newbie, I am appreciative of that.

 

As per this post: I do not have trust in Revit's ability to create accurate and reliable gbXML's. In addition, it is so hard to not get buggy models the more complex your model starts to get. I exclusively work with old existing building, so maybe my perspective is unusual, but every building I look at has geometric quirks (i.e. double roofs from 5 decades apart, partial walls, partial plenums, odd wall shapes, lots of abandoned chases/cavities/etc.) that result in their respective thermal quirks that I believe should be reflected in the gbXML that Revit creates. Unfortunately, Revit is just not there yet. Too many work-arounds and bugs prevent this.

Message 15 of 31
RIPENG
in reply to: Iev60047

@Iev60047thanks for the detailed response sharing your experience with gbxml and TRACE3D. With TRACE700 coming to an end Ripcord has been surveying replacement options with the goal of determining where to head next for building analysis software. I would certainly like to connect and hear more about your experience with TRACE3D since it seems like we have similar ideas in mind when it comes to modern analytical workflow.

 

As far as gbxml production is concerned, Ripcord's workflow has evolved somewhat since my last post. In the end, I found it was more productive to go backwards to go forwards. The following describes current workflow:

  1. Detailed elements (wall, floor, roof, window, door) are used to create an exterior shell.
  2. Space separation lines are used to designate Spaces.
  3. Dynamo is used to transform Spaces into Masses.
  4. A 'Mass' gbxml is exported that (usually) accurately captures surfaces.
  5. A 'Space' gbxml is exported that accurately captures openings.
  6. A Ripcord custom gbxml utility is used to combine 'Mass' & ' Space' gbxml to yield a single gbxml with accurate surfaces & openings.

More information about Ripcord's custom gbxml utility is located on gitbug at jpstaub/gbxmlMerge_streamlit. Demo gbxml files can be found in the same repo.

 

-Jake

Message 16 of 31
Iev60047
in reply to: RIPENG

@RIPENG thanks again for your contributions to a dynamo script and workflow for working with Revit gbXML's and Trace3d! I haven't had the luxury of time to explore your tool and that workflow (I am currently using Trace 3D to help me select an air handling unit and also examine several building modification alternatives which is much more time-consuming than I thought would be to learn). 

 

I shared the repo with my colleague and we are both interested in trying the workflow out for the first time. It's nice to see that other engineers are working on the same kinds of modeling challenges. 

 

And yes, I'd love to connect and talk about this if once I get wrapped up with this project. My email is: iev60047@uga.edu.

Message 17 of 31
LjubanL
in reply to: mbeckwithUMVQ6

Hi,

 

A really interesting topic, not only in terms of the discussion about energy analysis, but also the discussion about Autodesk and the development of Revit as a software.

When I started working in Revit (and a lot of time has passed since then), I remember how much enthusiasm there was.

Revit was software that was meant to rule all other software (like the Ring in Lord of the Rings).

Energy analysis/calculation of pressure drops in ducts /distribution/calculation of pressure drops in pipe distribution...etc.

It was imagining software for engineers - designed so that I can complete whole project without opening five other software.

You are talking here about exporting gmbx to some other software for energy analysis, and you forget that revit has the same analysis in it - which has not been updated for 15 years - with a lot of errors (detailed discussed on hundreds of topics)-I didn’t tested what happen with this functions few years because we buy plug in to that-but I was wonder what happen with that function.

 

We buy a product and when we buy it - we realize that there are errors/calculation errors in it and then this error stay with us many years - we waste money on it - would you buy a car if the seller tells you that his wheel does not work, but you can buy the same wheel from another company and everything will be ok.

 

Also, a quite frequent topic on this forum is about the calculation of the pressure drop in ducts and ASHRAE tables in revit (no one even mentions calculation for pipes anymore 😪) And no one knows how it really works - ASHRAE tables are a bigger mystery than the Egyptian Pyramids/ Roswell/Area 51/ assassination of John F. Kennedy…etc 😀

 

-Routing preferences in Revit have not changed for 17 years - for the same pipe, I need to have two or three routing preferences because it cannot have a tee and a tap in one preference-its impossible add some rules. Flange also…

 

-if you do ductwork in revit and client ask you to provide area of this duct 🙂 for area of the fittings you need to ask Dr. Strange because only Dr. Strange&Scarlet Witch can help us 😀.

 

How many things has Autodesk upgraded for REVIT M and P (mechanical and piping) users in these 15 years?

 

I remember only one thing – I think in 2014 or even 2015 revit allow as to put grill on duct 😂 - yes my dear friends before that it was pain in a if I want to put grill directly on duct.

Etc etc...

 

I would like to say that its not idea to criticize Revit – I like to work in Revit (and it is not Stockholm syndrome 😀) and I think it’s the best software on market. I criticize the lack of will to correct an error in the software - especially if the error was detected and reported.

 

Now a few words about gbxml - I remember when I was exporting to gbxml from Revit to HAP that there was some limitations when I try to import gbxml in software like HAP (if I remember correctly, hap could only insert eight surfaces for one room)- so sometimes you can prepare perfect gbxml with all data but software importer doesn't support this.

 

A lot of things I typed by hand. The same thing happened with trace - the worst thing is that a bunch of rubbish gets into the software which you can only see at the end or even worse when your superior sees or even worse client 😂 and time is running out.

 

I remember what I do few times (sketch up was still free), open studio/legacy open studio had a plug in for sketch up - so I quickly recreate the building- it was just box –sketch up was great tool to do this and then assign properties to it and then export gbxm to software hap or trace or continue with os - that gbxml was excellent quality and quite updated.

But if the building changes, I did the changes manually (and it always changed) 😰.

 

I remember that I also try to create gbxml room in autocad mep and than export to other software – but I noticed that floors was exported as roof, interior walls as exterior walls….

 

BR

 

Ljuban

Message 18 of 31
dyp4f
in reply to: LjubanL

Revit is the best among the other existing pieces of software of that kind, but that is not enough for the MEP Engineer. We can do the 70% of MEP Systems Engineering / Design / Modelling in Revit, but the missing 30% is crucial to complete our job. Other pieces of software are indeed even worse but that does not solve our real problem.

 

They seem to keep Revit MEP underdeveloped on purpose. After so many years, there is no other explanation for us but to assume that they have some purpose, or some real problem, or both. After so many layers of patches during all these years, maybe the core of the software has become so excessive complicated that nobody can (or dares to) rewrite a serious block of code inside it, anymore.

 

I can see 2 future solutions for the MEP Engineer:

 

1) A brand new BIM MEP Software emerges and takes on the MEP Engineering market

2) Autodesk sets up and prepare a powerful Artificial Intelligence to undertake the task of developing the software. After deploying that AI, Revit human developers get fired !

Message 19 of 31
iainsavage
in reply to: LjubanL

Regarding sketchup, Autodesk have their own version called Formit Pro which is included in the AEC subscription. Maybe that does what you need for creating rough models?

https://www.autodesk.com/products/formit/features

 

As for the rest of your post, I agree that it is so disappointing that the same faults and problems have existed for years and never been corrected.

Message 20 of 31
LjubanL
in reply to: dyp4f

Hi @dyp4f 

 

There is also a third option:

 

-Autodesk starts working with us on improving the software

 

-If error is noticed - Autodesk removes the error within a reasonable time (less than 10 years 😂 )

 

-Autodesk hires engineers who have worked on real projects - who would serve as advisors to the programmers who write the programs.

 

-Autodesk accepts responsibility if an error in the software creates a problem on the project and creates a huge cost-money/deadlines.

 

- at the end we hug each other and sing kumbaya - and unicorns jump around us 😀.

 

Unfortunately, that won't happen - big fish eat small fish.

 

As for the appearance of some new software, I really doubt it - if it does appear if they feel any threat, they will simply buy it...like facebook or microsoft ….

 

I wouldn't dare to say that Autodesk keeps the software underdeveloped - because if that's true, it can be brought under a criminal offense (and that's a job for the relevant institutions).

 

My opinion is that Autodesk has become a huge company - these huge companies are losing touch with reality and with their customers.

 

This can be seen on this forums - why wouldn't Autodesk hire 3 people per software to provide proper support.

 

Some forums are totally dead like autocad mep - people write and ask for advice, but most likely no one will answer.

 

BR

 

Ljuban

 

 

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