WARNING - Revit 2016 & Pointclouds insertion

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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by jamesworrell »

Best I figured last time I looked at it - it was a significant figures issue with the conversion to feet internally in Revit. The offset was about 600mm or so .. and the last digit accounted for it.

If you get into the type properties for the point cloud family .. you will find a scale of 3.280840.

Try 1 foot = 0.3048 metres .. 1-on-x .. 3.28083990 .. with the sort of coords your are talking about, the scaling from origin becomes an issue.

You can try to set the conversion factor to a better precision .. but it rounds it back up.

We gave up .. you could try exporting from cyclone in feet perhaps or some other hack. We simply truncate the leading x-digits.

See attached ..
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by jax120 »

Hi James

I thought the same about scaling too, but in Revit 2014 it has the same Scale digits and that works fine.

So I did a bit of investigating and have done some screenshots and now I'm even more confused with my findings.

The below image is from Revit 2014 (with Update 3) I have inserted a pointcab image to verify the pointcloud and project is now on shared coordinates of around N/S6248045662.6, E/W 333130058.6mm. Bot pointcab and pointcloud are inserted 'by shared coordinates'
The pointcloud (Blue) perfectly overlays the detail in the pointcab imagery (greyscale). And this has always been the case since Update release 3 for revit 2014.
RVT2014.png
As I upgrade to 2016 the following image happens.
RVT 2016 PROJECT UPDATED.png
As you can see, the offset is very noticeable (about 400mm). So I tried setting up a new project in Revit 2016 with an old 2014 template and the same thing happens.

But here's a kicker, when I started a new project with a 2016 Template, this happens.
RVT 2016 NEW PROJECT.png
RVT 2016 NEW PROJECT 2.png
So it first appears ok but when you zoom in there is a slight offset (40mm)
Also noticed now this happens in 2015 too.

Is there any reasoning behind such inconsistent program behaviour.
It seem they got it right for Revit 2014 Update 3, but forgot to carry any of this programming over to 2015/2016

The worry also is, if it is a slight scaling issue, then surely this would affect origin to origin on local pointclouds too, only slightly less. But still may be noticeable on very large project, I mean we maybe talking a couple of mm, I'm not sure, but still worrying.

Is this issue well known to Autodesk? I know it is on here, but there could be a lot of pointclouds/models going out that are not near its intended position. And anyway if it is known then why is the 'by shared coordinates' option even available?
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by Matt Young »

All you need to do is create a point cloud origin close to the point cloud, preferably lower left corner to allow positive coordinates. Make sure you know the move in x and y from the large system.

Also better to set the building square to grid (this can be tricky if you don't have the right software). Insert the point cloud origin to origin with the new local system. Then input the large coordinates and rotation into the shared site marker.

Even when creating models in AutoCAD on large coordinates I move the model to the origin for the work and move back when finished.

It's does not really matter which version of Revit you are using for this - close to origin should work.

I might be wrong but I believe that for Autodesk to fix this 100% then they need to do an awful lot of work.
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by jax120 »

Sorry Matt

But I know I can do all this, I know the answer. I've been doing this for 10 years, it just gets me that why should we have to, as I was saying in the previous post this was all fixed to work in 2014 and this is right workflow, in my opinion it's wrong to drop coordinates. for the sake of Revit but yet that the option (by shared coordinates) in the software is still there but can't perform to do it. and then we have export reacap again for people who want clouds on real world coordinates if we do drop coordinates.

Why should we have to drop coordinates for Revit, THEY MADE IT WORK for 2014, now it does'nt for 2015/2016, and yet the option remains

Can we stop with the replies of the only answer is drop coordinates because that is not the answer to software designed by a multi billionaire company. And not the answer to the real issue here.

As I said there is no real work for autodesk to fix 100%. They fixed it already for REVIT 2014 update 3., Try it. It works

But if something does go wrong can we send the bill to Autodesk?
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by 72RPG »

Hi Andy

I am using workflow (more- less the same) as Matt described and it works.
And for our contractors/architects i have 2 ReCap files -one in local grid - for Revit and one in large(ITM) coordinates for Naviswork, AutoCad BIM 360 glue.
This is project
in ITM (for another applications)

in Local Grid- I imported grid lines to Cyclone (we use to divide scan data to several zones based on grid) - with Project Base Point from Revit
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by Matt Young »

It's not wrong to drop the coordinates, the building was not designed on large coordinates. It makes perfect sense to work on a local system and assign a global system afterwards. If I am honest I have never really seen this as a broken item in Revit, It's just the way surveyors think. If you reverse engineer a building then you need to reverse everything to do it properly. Modelling on large coordinates is not wise and there is too much room for error, end of story.

Those examples of the grid in Cyclone are perfect, exactly what need to be understood. You can create a grid for a building if it does not have one as well.
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by jax120 »

Maybe I Just got used to Revit 2014 then when this worked, and now the only answer is to drop coordinates on the cloud. And it's not a real issue for Autodesk then - Ok Autodesk carry on what your doing.
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by james.still »

jax120 wrote:Maybe I Just got used to Revit 2014 then when this worked, and now the only answer is to drop coordinates on the cloud. And it's not a real issue for Autodesk then - Ok Autodesk carry on what your doing.
it will become part of the work flow using a truncated point cloud, we are adopting this approach.

This is something that needs agreeing and putting in the BEP from the beginning about the truncation of the model and point clouds, also, what your model will be delivered in (large or local co-ordinates) when it is completed.

Autodesk are getting pressure about this, as addins from Kubit and Edgewise do not work with large co-ordinate point clouds in Revit 2015-2017.
This is because snapping to the point cloud does not work, so in turn this disables their addins from interrogating the point cloud.
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by jamesworrell »

To be perfectly fair, geodetic coordinates are somewhat dangerous anyway due to the ambiguity surrounding the scaling factor.

It is fairly risky, esp bigger sites where the factor has more impact .. but when seeing geodetic coords, a user needs to know, is the file "pure UTM" or "pure MGA" for example in our case down here (scale factor ~ .9996 say), or is it good old plane/metres, where you need to agree on a "control point" to scale from when aggregating/handling any "pure UTM" data.

Try having a conversation with someone about "metres aren't really metres" etc .. and watch their eyes glaze over.

The cloud files can't typically store much meta data, so hopefully it is sent with some in supporting docs, but then it is forwarded etc and gets out in the wild.

You could be tempted to export local coords/plane/metres based on an arbitrary or truncated origin, but then also have a pure geodetic file including the appropriate scale factor applied for the location. Or supply truncated with meta data nominating the translation and scaling factor to get it back to a UTM projection.

Which leads on to the inconsistencies in versions. The recap file format has no doubt changed a bit over time for performance or other reasons. Perhaps the software processes differently .. bounding box plus translation say, different ways to organise the data structures (quad trees whatever) .. who knows. The file format also no doubt has to support some backward compatibility. Bit of a moving feast.

I do find it curious .. a lot of other linked/inserted stuff in Revit from memory has a specified units and scale.
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Re: WARNING - Revit 2016 & Pointclouds insertion

Post by Matt Young »

Interesting article relating to the same issue with AutoCAD - from Autodesk:

https://knowledge.autodesk.com/support/ ... space.html
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