Export gbxml coordinates precision

[Anonymous]

Hi everybody,

I have an issue with my gbxml export from revit:

Is there anywhere in Revit that we can set the number of decimals for the gbxml coordinates?

In fact, the gbxml coming from Revit has only one decimal in the coordinates, which is not precize enough in my opinion.

When importing that gbxml file into and thermal simulation tool (IES VE), the edges don't match.

I suspect it's because of the edges coordinates that are rounded up.

And changing the export complexity doesn't solve the problem.

Thanks in advance for your answer.

Bianqui

[Viveka_CD]

Hi @Anonymous

Thanks for posting on our community forum!

Please see the article HERE for Exporting to gbXML and please see the Energy settings that control the behavior of the energy model creation

Is it possible to share a Revit file and the gbxml log file with us to troubleshoot further? I can send you a private folder to upload.

Looking forward to your reply update.

Regards,

[Anonymous]

Hello,

Please find in attached an example of a Revit file and the gbxml exported by Revit.

To open it, I use IES VE tool and the result is the same: rooms intersect and edge don't match.

Best regards,

Bianqui

[Viveka_CD]

Hi @Anonymous

Thanks for sharing these files. 

We will troubleshoot and let you know for an update.

To make sure that the issue you are seeing is not something already fixed in one of the product updates, I would suggest checking the Desktop App to see if there are any Revit updates available. For information on using the Desktop App see the following article: About the Autodesk Desktop App

Note: If you are not able to download updates through the Desktop App, the following article has information on downloading updates through the Autodesk Accounts page:

Install Updates, Add-ons, and Enhancements

Regards,

[Viveka_CD]

Hi @Anonymous

On testing your file, the project coordinates are located very far from 0,0 this can lead to data corruption.

gbXML is not limited to 1 decimal place. This could be related to the numerical stability issue. 

Also, see the article on Revit gbXML exported geometry contains gaps

Please reset the origin and try exporting again. See HERE for more information on moving Project Base Points and Survey Points

If you find posts have solved your problem, please click on 'Accept as solution' to help others with similar questions. Kudos welcome.

Regards,

[Anonymous]

Thanks for the answer.

To use the rooms/spaces seems to be the most accurate way of exporting gbxml.

That's why my question was about to know whether we can change in Revit the number of decimals of a gbXML coordinates before exporting?

Bianqui

[Viveka_CD]

Hi @Anonymous

Unfortunately the decimal places cannot be altered.

See this article HERE that talk about geometric accuracy and best practices.

• There have been reports of inaccuracy in coordinates at importing point clouds from Recap to  Revit 2017.When indexing point clouds that are on large coordinate systems, from PTS to RCS, there is a constant shift of 20mm.

• If your data originates from 2016 version, After you upgrade to the 2016 version of the model to 2017 or 2018,  point cloud link should be first removed then re-added again instead of reload.

If you find posts have solved your problem, please click on 'Accept as solution' to help others with similar questions.

Regards,

[evgeny.kurbatov]

@Anonymous 

Here are the Project Base Point coordinates (in millimeters) in Revit:

It is approximately 4.8 thousand kilometers away from original point.

In the resulted gbXML file the coordinates (in meters) for surfaces appear like this:

As we see the numbers are truncated to 7 digits. It means the precision is 0 000 001 (one meter)!

The result you can see on the picture - the building is broken:

If we place a project more than 10 thousand kilometers from original point the precision will be 10 meters!!! It is absolutely not enough to represent data correctly. I strongly believe that precision should be not less that 1 millimeter. 

Let's count how many digits do we need. The Earth perimeter is approximately 40 000 km, or 40 000 000 000 mm. The maximum N/S or E/W distance to a project base point is the half of that number. But anyways it is a 11 digits number. To be precise we can have 1 digit after decimal point in millimeters, which require 12 digits for coordinates in gbXML file.

[RobDraw]

See the first sentence in message 5 of 8.

[evgeny.kurbatov]

> See the first sentence in message 5 of 8.

------------

The sentence is: "the project coordinates are located very far from 0,0"

Do you think it is a good excuse for the broken building model?

[RobDraw]

What I think does not matter here. It is a known issue. Coordinates very far from the origin require a lot of calculating to be accurate. The program simply struggles with these computations.

Good luck!