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Messages - Arie

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76
General / Re: FF camera questions: a7Rii vs. D750/810
« on: March 30, 2016, 03:49:30 PM »
It is possible to deactivate image stabilisation, because this can have an impact on image sharpness when activated using a tripod. Here's a test from Jim Kasson: http://blog.kasson.com/?p=8391

77
General / Re: FF camera questions: a7Rii vs. D750/810
« on: March 30, 2016, 12:58:08 PM »
Hi,
while not having used the D800 / Sony A7 II I do have a A7R as well as a Nikon D600. To be frank, I am currently selling off most of my Nikon gear.
As you mentioned, using a bulky DSLR with good lenses such as the Sigma Art 35mm f1.4, can be quite cumbersome when using it all day (though it is a free workout). I personally really love the EVF of the Sony A7R, which is more easy to use than an OVF, since you see what you get, making for example precise focusing much easier. One of the other main reasons for switching is that I can use the A7R airborne as well as terrestrial, the Nikon is just to heavy for that (and I don't need a mirror when using it with my UAV).
Of course, there are some drawbacks to Sonys new Alpha series; since it's a comparatively new system the available lenses are fairly expensive. Sony/ Zeiss has been on a roll releasing wonderful lenses, such as the Batis (25mm, 85mm) the Loxias (21mm, 35mm, 50mm) or Zony lenses such as the small 35mm 2,8 or the incredibly sharp 55mm 1,8.
Furthermore there are hundreds of lenses, which can be adapted, though most adapted wide angle lenses do not work as well as native lenses (corner smearing, color shift).
But of course Nikon can hold its own regarding lenses, Sigma Art, Zeiss Milvius/ Otus are some of the best lenses out there. And one has a wide range of legacy lenses, which can be quite cheap (compared to the other mentioned ones).

Regarding the comparision of ISO, dynamic range and resolution between the D810 and the Sony A7RII, you should just check the usual photographic sites such as dxomark, dpreview etc. to decide if the difference between the two is neglible for you (spoiler alert, the difference between the two is not huuuge!).

At the end of the day, it would seem to me, that choosing one system over another is largely dependend on your personal preferences. Both mentioned cameras are top of the line regarding full-frame image quality. Sony has not quite matured yet (in my opinion) but is on a roll regarding technological innovation.

Cheers!

78
General / Re: Advice for Workflow on big area in city needed
« on: March 29, 2016, 12:56:39 PM »
Hi Luciano,
sorry for the late reply.

Are you talking about registering a dataset without common GCPs?
Cheers.

79
General / Re: Room scan - Getting rough uneven walls on mesh
« on: February 27, 2016, 02:02:36 PM »
Shouldn't be a problem, as long as you keep the orientation and scale of the two datasets aligned- sometimes the units or the axis differ between software packages.

If your clean model has a new uv-map just make sure to check "keep uv" during the texturing stage (under Mapping mode) .
Cheers.

80
General / Re: Quality of mesh question
« on: February 27, 2016, 01:57:02 PM »
You should check out the "Face and Body Scanning" section on this forum for more tipps on faces.

The noise is most likely the result of using just a single camera. The person would have to hold perfectly still, which is practically impossible.
Cheers!

edit: you might want to try to use aggressive filtering on the dense reconstruction step. It might smooth out things a little more. Additionally you could use the "smooth mesh" command.

81
General / Re: Advice for Workflow on big area in city needed
« on: February 10, 2016, 06:27:01 PM »
You can use Agisoft to texture laserscan data.

After aligning and referencing the images, just import the referenced mesh of the lidar data and texture it.
Just make sure, that the referencing of the lidar data and the images is accurate (using dgps or total station for GCPs). When the alignment between the datasets is not good enough, there will be some errors in the texture map.

In case the aligment based on reference markers isn't precise enough, you can export a mesh of the dense reconstruction and align it using an ICP approach such as implemented in Cloudcompare.

I do this regularly and it works great.

82
General / Re: Best strategy to scan thin objects on turn table
« on: January 27, 2016, 11:19:53 PM »
The results you posted show clearly some limitations of photogrammetry. But with these type of objects I would guess even structured-light scanners would struggle (depending on the accuracy requirements and preparation work).
Two things that immediatly come to mind is the uniform surface color of the glasses frame and the shininess of the surface. Both individually are bad, combined even worse and I don't think you will be able to achieve any kind of good results.

My suggestion would be to coat the frame with some diffus reflecting substance (spray paint, for instance) and additionally trying to get some texture onto it (splashing some acrylic paint or similar).

For thin objects there has to be a fairly high amount of overlapping images, since the surface changes rapidly when only change the rotation slightly (especially in vertical direction). It is a good idea to have a well textured background as long as it stays in the same position relative to the glasses.

Also try optimizing the image-framing of the glasses, they should be covered by as many pixels as possible.

Good luck! Quite a challenging subject you have there.

83
Feature Requests / Re: Refining generic alignment
« on: January 27, 2016, 07:02:52 PM »
So, i've tried to replicate the situation and stumbled across some issues.

Since the original dataset was too large I just ran several alignments on a subset of the imagery in the area where larger errors occured. Interestingly enough, suddenly I was not able to align all the images using the "generic" option.

Attached are some screenshots, the original "generic" alignment was done with a version before 1.2. Here one can see the error in the dense reconstruction, that occurs between two rows that do not have a lot of overlap. Next to that screenshot is the dense reconstruction based on the "disabled" option. The errors are gone.

With 1.2.3. I can't get the two rows to align at all using the generic option. The "disabled" option on other hand aligns them without a problem and the dense reconstruction shows no errors.

The difference time wise is 7h 28min for disabled vs. 50min. for generic, which brings me back to my original question. Any chance on exposing the generic parameters (for example as advanced settings)?
Cheers!

84
Bug Reports / Re: Build Mesh stopped working in PhotoScan 1.2.3
« on: January 27, 2016, 05:37:53 PM »
I just did some meshing with 1.2.3. and it worked fine for me.

Arbitrary
Dense Cloud
Face count 0 (max.)
Interpolation Enabled (Default)

Build 2331 64-bit on Windows 7 Pro x64

85
Python and Java API / Re: Aligning chunk based on 4x4 matrix
« on: January 27, 2016, 05:07:39 PM »
Hi Alexey,
thanks for the quick reply!

The datasets have been processed in two seperate project files. One of the projects has been referenced using markers while the other project hasn't been referenced. I've exported both dense pointclouds and aligned them using Cloudcompare, resulting in a 4x4 matrix (http://www.cloudcompare.org/doc/wiki/index.php?title=Apply_Transformation).

So I was wondering if this can be used to reference the previously unreferenced project file for exporting DEM etc.

I could upload both project files, but the internet connections I have here is terribly slow and unstable.
Thanks for your help.


86
Python and Java API / Aligning chunk based on 4x4 matrix
« on: January 27, 2016, 04:32:28 PM »
Hello,
is it possible to align a chunk (translation + rotation) based on a 4x4 matrix?

I have a couple of datasets, that have been referenced by overlapping areas using an ICP algorithm (done in a different software). I have the 4x4 matrix of the transformation and would like to use that for referencing the chunk within Photoscan for DEM creation etc.

Cheers!

87
General / Re: Sony a7r triggering
« on: January 27, 2016, 01:07:43 AM »

88
Hi,
a while ago I did some test with 16-bit vs 8-bit images. I'm currently abroad, so I can't post any screenshots of the results, I'll see that I get that posted when I return.

If memory serves me right, regarding the reconstruction quality there was no visible difference between the 16-bit or 8-bit imagery. I'd have to check again if I ran everything on ultra, I could imagine that JPEG artefacts could cause some noise. I'd guess the imagery must be of really high quality regarding pixel sharpness, ISO noise etc. before this could become an issue and, of course, is dependend on the compression level and quality of the used JPEG engine.

Where the difference between 8-bit and 16-bit should have an impact is high contrast scenes. In 8-bit imagery highlights and/or shadows tend to clip more rapidly and when there is no more/ little information, of course, nothing can be reconstructed.
Most modern DSLRs have about 14-bits of information, which can be seen when lifting shadows or darkening highlights when processing the raw images. I know this type of image processing also can cause artefacts, so it might be better using the 16-bit data instead of compressing the total tonal range into 8-bits (but this is just an assumption).

Where I tend to use 16-bit tiff imagery is when color tonality is key. For example, I recently documented about 100 large scale stucco ornaments under exactly the same lighting condition and for keeping the fine color details during the entire workflow (until the finalised visualisation) I used 16-bits all the way.

Regarding andyroos original post; having DNG support would be absolutely awesome, especially if it would be possible to export the texture-map in DNG format (similar to Lightrooms recent support of stichted panorama imagery in DNG). This would give one a great control over colors (white-balance, color space etc.) even after the models have been processed.

Cheers.

89
Feature Requests / Re: Refining generic alignment
« on: January 25, 2016, 05:54:27 PM »
Ups, sorry for throwing undefined terms around. I mean increasing the accuracy of the camera alignment.

I'll give your suggestion a try, do a comparision and get back to you.
Cheers.

90
Feature Requests / Re: Refining generic alignment
« on: January 25, 2016, 05:33:32 PM »
Hi Alexej,
in this case it's not about using gps-coordinates but rather refining an existing alignment. I've had a couple of cases where generic alignment delivers fairly inaccurate results, so I was hoping to refine the alignment using the computed poses for a more accurate alignment.

Of course, being able to decide oneself if accuracy or speed is prefered, would be ideal (setting parameters for generic).

Thanks for your reply.

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