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Author Topic: Making measurements of a 3D Photoscan model  (Read 16050 times)

tenboair

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Making measurements of a 3D Photoscan model
« on: September 17, 2014, 10:33:34 PM »
Does anyone know of a good method to measure dimensions of a Photoscan model? For example, I want to pull dimensions of a roof from a model that's georeferenced. CAD software doesn't seem to keep any kind of scaling information from the model, so it has no idea how to scale the dimensions. Google Earth works fine with 2D orthomosaics, but doesn't seem like a good tool for measuring 3D models.

Ideally, I would like to use the GPS information and reconstruction geometry to generate measurements without ever physically measuring a part of the model.

Patribus

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Re: Making measurements of a 3D Photoscan model
« Reply #1 on: September 19, 2014, 10:42:53 AM »
I'm also interested in this....

ISeeBees

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Re: Making measurements of a 3D Photoscan model
« Reply #2 on: September 19, 2014, 11:36:38 AM »
I'd also like to do this and don't know directly how. It seems that it should be possible as the focal length of the camera is known. My current solution is to measure several distances on what I'm imaging, and then to scale the model such that those dimensions are correct, but its non-ideal work around.

JMR

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Re: Making measurements of a 3D Photoscan model
« Reply #3 on: September 19, 2014, 02:01:08 PM »
Inside Photoscan: After the model has been georeferenced. Put markers at the ends of the line you want to measure (You can do it directly on the model and adjust precisely their position on each photo where the marker is back-projected). Select the two markers in the project tree and create a ruler object by right click.
Then you can read the measurement if you select view estimations in the ground control pane.

ISeeBees: If no geo-reference nor direct scale input has been done by rulers, you cannot trust any measurement from the model, not even if you know the focal lenght very well.

Outside Photoscan, you should be able to take measurements with most of CAD and GIS tools, but also with Adobe reader if you export 3dmodel as pdf. Try Meshlab too

Jose Martinez
GEOBIT

Patribus

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Re: Making measurements of a 3D Photoscan model
« Reply #4 on: September 19, 2014, 10:47:13 PM »
I have an object which I export from PS.

I have used meshlab to do virtual cuttings through this object creating a closed border line.

MY question: is it possible in Meshlab to calculate the length of a closed line?

Cheers

tenboair

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Re: Making measurements of a 3D Photoscan model
« Reply #5 on: September 23, 2014, 10:28:18 PM »
Jose,

I'm struggling to import the photoscan model into a CAD platform. What CAD does it work well with? It doesn't work well with Solidworks or ArchiCAD. Haven't tried AutoCAD yet.

Many of the file types simply crash SolidWorks or ArchiCAD.

Please suggest a user-friendly/easy-learning curve program that I can import a Photoscan model file into.

JMR

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Re: Making measurements of a 3D Photoscan model
« Reply #6 on: September 24, 2014, 12:25:36 AM »
CAD is not the way to go for large polygon count meshes and even worse for dense point clouds unless you have specific plug-ins. You should better try with software packages designed to handle laser scanner data if your field of application is mainly close range; or, just use GIS tools if your field of application is Geomatics.
Georeferenced data are usually rejected by programs that are not intended for handling large numbers coordinaes (UTM), so what you could try is to translate your model so to a place its center near the (0,0,0) by using a big integers vector during export from photoscan to Solidworks. I have never tried with that program, but it happens with others.
You will find much more usable photoscan models exported as DEM inside GIS tools, you can also make good use of the dense point cloud with programs developed for lidar data.
Regards
PD, if you specify your need I may suggest a finer approach

tenboair

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Re: Making measurements of a 3D Photoscan model
« Reply #7 on: September 24, 2014, 03:54:25 AM »
That's good to know, thanks!

I'm interested in taking photos of a roof, reconstructing it, and then being able to pull dimensions from the model. Basically, I need a way to take 3 dimensional measurements. There are probably some GIS programs that can do this, but optimally we could work it in to our current workflow.

Can you suggest a GIS program for me to try doing this with?

JMR

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Re: Making measurements of a 3D Photoscan model
« Reply #8 on: September 24, 2014, 04:21:43 PM »
For such an easy task, it may be just enough to take measurements in:
Meshlab, Cloudcompare or even Adobe reader out of 3d-pdf like in the example.

tenboair

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Re: Making measurements of a 3D Photoscan model
« Reply #9 on: September 25, 2014, 12:08:32 AM »
3D models in Adobe Reader?? You just blew my mind. Thanks!

chrisd

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Re: Making measurements of a 3D Photoscan model
« Reply #10 on: September 25, 2014, 12:39:02 AM »
Adobe Reader works well if you have up to few hundred thousand triangles. It starts to really slow down over a million triangles. Most likely you will have to decimate. Its still only a 32-bit application, so even a high end system does not improve the performance with larger models.

David Cockey

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Re: Making measurements of a 3D Photoscan model
« Reply #11 on: September 25, 2014, 05:10:45 AM »
Rhino3D works for me for meshes up to 20 million faces or so.

chrisd

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Re: Making measurements of a 3D Photoscan model
« Reply #12 on: September 25, 2014, 06:01:28 AM »
Rhino3D works for me for meshes up to 20 million faces or so.

That's really good to know. I never think of using Rhino for meshes.