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Messages - Nathan Craig

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Camera Calibration / Re: Use of Macro setting when calibrating a lens
« on: June 27, 2011, 06:58:06 PM »
Dear Alexey,

Thank you for the clarification. This is quite useful information.


Feature Requests / Re: Additional batch options
« on: June 27, 2011, 06:55:16 PM »
Autosave of processes started outside of batch would be useful.

Camera Calibration / Re: Use of Macro setting when calibrating a lens
« on: June 26, 2011, 01:58:22 AM »
Hi Alexey,

Thank you for the information. If I understand correctly, if the images for a model are shot at infinity it is desirable to have the calibration images also shot at infinity. The focus point influences the calibration. To attempt to achieve focus at infinity using Agisoft Lens, I should strive to use a large monitor, high depth of field, and a tripod. It may be challenging to find a monitor large enough to fill the field of view when the camera is at infinity.

Can Agisoft Lens perform a calibration from some other regular grid? For example, a large printed array of black and white squares or a building with very regular squares. With other lens calibration systems, I've used large printed sheets or images of buildings with regular squares. Might such images work with Agisoft Lens?

Thank you again,

Camera Calibration / Use of Macro setting when calibrating a lens
« on: June 24, 2011, 05:59:37 PM »
Most of the images I process in PhotoScan are taken from a kite and the lens is focused at infinity. To calibrate a lens using PHotoScan Lens, I must move the camera close to the computer monitor. So close in fact, that I must use the camera's macro function. Should I expect the use of a different mode to have a significant impact on lens calibration?


Camera Calibration / Re: Square Pixels and Center Principal Point
« on: June 23, 2011, 12:13:54 AM »
Dear Alexey,

Thank you, this is much clearer now.


At present, PhotoScan can display EXIF data (like camera and focal length) that are relevant to selecting the appropriate calibration. The calibration input interface permits the input of specific calibrations. For projects that use multiple cameras or focal lengths, it would greatly streamline the selection of the correct calibration files to have the relevant EXIF data also displayed in the calibration input interface.


Camera Calibration / Square Pixels and Center Principal Point
« on: June 21, 2011, 07:56:48 PM »
In the Calibration dialogue, there is an option to set Square Pixels. The word square is not presently found in the PDF version of the manual for Agisoft Lens. In the manual, under the section on calibration parameters there is a discussion of fixed aspect ratio. Does this option relate to the square pixels option? Likewise, the manual discusses "Fix Principal Point" while the options dialogue box reports Center Principal Point. Should I assume that these are likewise related?

Thanks in advance for any clarification that can be offered.


General / Re: Photoscan vs laser scanner - lidar
« on: June 21, 2011, 06:23:20 PM »

I'm very much looking forward to reading your paper. Your last publication on PhotoScan was quite good.

Warm Regards,

General / Re: Adding Precision Markers
« on: April 09, 2011, 07:50:42 PM »
Thanks Matt, that is useful information regarding the markers. Also, the ability to create DEMs from archival aerial photograph is quite interesting. I've tinkered with this only a bit in terms of trying to reconstruct archaeological mounds that are now destroyed but visible in old aerial photographs.

General / Re: Re: Adding Precision Markers
« on: April 02, 2011, 08:43:41 PM »
If markers are placed on the models and then marker positions are refined in each of the photos, does this update marker position on the model? Often times, it is difficult to get highly accurate placement of the targets on the models. This is because textures are more coarse than the source photos and because I use colored photo targets that are flat and don't produce sharply defined features in the models. In other words, markers are placed on the model largely based on the textures but the textures are not as finely resolved as the source photos. The textures do provide sufficient resolution to place markers, but marker position can be refined by returning to the source photos. However, I am not clear if calibrating marker position on the source photos has any impact on maker placement on the model. Is this the case?


General / Re: Loading textured OBJ files into MeshLab
« on: August 04, 2010, 02:18:57 AM »
Dear Dmitry,

With this method, I was able to load into MeshLab v1.2.3 a model exported from PhotoScan. To edit the obj file, I used Notepad++.

An additional note for novice users (I made the same mistake the first time around): be sure to replace the text "model" with the actual name of the model that is being modified. There are three places where the name of the model must be inserted: 1) the name of the .mtl file, the final line of the text in the .mtl file, and the text line that is added to the .obj file. When these three values are properly formatted, the file opened with out problem.


General / Re: Re: Re: Can't Build Model
« on: July 26, 2010, 03:59:49 AM »

Thank you for the updated build. At present my internet connection is not permitting me to download the new build, but I will likely be near a more stable connection tomorrow.

In the mean time, the build I have is running much more stable. I uninstalled it, restarted the machine, and reinstalled. It is running much better. As soon as I can download the updated build, I will begin working with it. Thank you very much.

I am grateful also for the detailed responses you provided in the the other threads.


General / What are Model Generating P1 and P2?
« on: July 25, 2010, 07:20:21 PM »
In the preferences, on the advanced panel, there are parameters for P1 and P2. What are these and what aspects of processing do their values control? How should users think about changing these values to improve processing? I checked through the manual and online documentation and did not see any mention of these parameters. Any guidance on the informed use of these parameters would be appreciated.


General / Can't Build Model
« on: July 25, 2010, 06:58:58 PM »
Very often I add a group of images to a project, orient the cameras, and proceed to generate the model. The model generation process begins but fails and provides the error, "Can't Build Model". I have had this happen with even small groups of images (4) that are of the original camera resolution (8 megapixel). I have also experienced this problem with larger groups of images (20-25) that are downsampled to 4 megapixels.

Recently, the application seems to be crashing more frequently and rarely generating models. Can you provide any suggestions for how to increase the stability of the application and improve chances of generating models after camera orientation? In the mean time, on the chance that the instillation is now corrupt, I will be reinstalling the program. If this solves the problem, I will report back.

Thanks for any help you can provide. This is a wonderful program, and I'm looking forward to learning how to use it as efficiently as possible.

General / Downsampled Images
« on: July 25, 2010, 06:45:08 PM »
I see that the manual states that one should, "se the original files from your camera whenever possible". Is it acceptable to downsample images? When working with Photosynth or Bundler, I regularly downsample images to 2 or 4 megapixels respectively. On my computer, SIFT does not process images larger than 4 megapixels. I see that PhotoScan will align the 8 megapixel images that are produced by my Canon S90 camera. I found that PhotoScan will in some cases also process images that are downsampled by the ImageMagik command "mogrify -resize". However, in other cases downsampled images do not appear to solve well. Is there a preferred method of downsampling, or is there a preferred ratio--say 50%.

I suspect that downsampling images permits the processing of larger collections. At a full 8 megapixel size, there is more information in the photos than is required. Downsampling, when it works, results in faster processing and models with acceptable levels of detail. I would be very interested to learn if there are any suggested "best practices" when it comes to software used and downsampling factor applied. Any help would be appreciated.


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