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Messages - David Cockey

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General / Re: Creating line drawings of models - which software to use?
« on: September 01, 2014, 07:36:25 PM »
I use Rhino to create lines drawings of boats based on PhotoScan models. I export the models from PhotoScan to Rhino as textured OBJ models (model names must not have spaces) and usually use "Render" mode for viewing the chunks in Rhino. I've been using version 5 of Rhino for quite a while but version 4 was satisfactory.

General / Re: Updating project with CalCam info - no error improvement?
« on: August 24, 2014, 04:36:55 AM »
PhotoScan solves for the camera calibration parameters as part of the "bundle adjustment" process when aligning the photos (unless "Fix calibration" is checked). It finds the best set of camera calibration parameters for the photos used in the project. The initial settings in PhotoScan are only the starting point for the iterative process of solving for the best set of parameters.

General / Re: Force camera to be used
« on: August 22, 2014, 11:05:53 PM »
Hi guys,

Thx for your answers,
The thing is, usually all cameras being aligned. However, when i start to create the point cloud, Photoscan doesn't use all the cameras. That is weird..
That's a different issue than camera alignment problems. Whether a photos is used in Build Dense Cloud depends whether the photo is included in a selected pair, and that depends on how many sparse points associated with a pair are inside the "box".

General / Re: Updating project with CalCam info - no error improvement?
« on: August 21, 2014, 09:40:37 PM »
My question above was intended for aggieair, the original poster.

aggieair, why do you think an external calibration should improve the results compared to the calibration PhotoScan does?

General / Re: Updating project with CalCam info - no error improvement?
« on: August 21, 2014, 06:40:53 PM »
Why do you think an external calibration should improve the results compared to the calibration PhotoScan does?

General / Re: Force camera to be used
« on: August 20, 2014, 07:51:59 AM »
Potential reasons for photos not aligning include insufficient overlap, insufficient visual texture, or poor quality images. If the photos show two different portions of the object with insufficient photos and overlap tying the photos together then one group of photos may not align.

General / Re: Best buy camera and lens?
« on: August 20, 2014, 06:29:39 AM »
Perhaps the considerations for aperture selection are different for aerial photography than for the close range photography of three dimension objects which I have experience with.

Selecting the aperture based on maximum sharpness as determined by a lens tests ignores depth of field. Lens tests only report the lens sharpness for a flat subject with the cameral perpendicular to the subject.

Depth of field can be ignored ff the subject is almost flat and all photos will be taken perpendicular to the subject or if the photos are taken at a sufficiently large distance. Otherwise depth of field matters, such as for close range photos of three dimensional objects.

Optimizing sharpness over a three dimensional object at close range may require using an aperture smaller than the optimal aperture from a lens test in order to increase depth of field and improve sharpness away from the focal plane.

Shutter speed may or may not affect sharpness depending on the light conditions, if the camera is moving or static, and camera support or stabilization used. If a sturdy tripod is used then shutter speed is generally not an issue if the subject is static. If the photographs are taken outside during the day then typically the shutter speed will be sufficiently fast for hand held photographs of static objects, assuming the person holding the camera is on solid ground.

The amount of light on sensor at f:8 is one-half the amount of light at f:5.6 (not "3 times lower") which would result in a shutter speed twice as long, or an ISO setting two times larger.

Large maximum aperture lenses are more expensive. Whether they will result in higher image quality for photos taken for PhotoScan will depend on the circumstances.


General / Re: Automated masking issue
« on: August 19, 2014, 11:05:47 PM »
Is the object on a turntable with a fixed camera location relative to the background, or is the object fixed relative to the background and the camera moving?

If the object is on a turntable with a fixed camera location relative to the background then there is a process to generate masks starting with a photo of the background without the object. I've never used that process so I don't know the details but it appears to be as simple. Try right clicking on a photo, then select "From Background" as the method. Click OK and you will be asked to select the background photo without the object.

If the object is fixed relative to the background and the camera moving then try this process:

First build a preliminary model:
Align the photos without masking. Low or medium accuracy should be sufficient.
Build the Dense Cloud. Low or medium quality should be sufficient. Trim the dense point cloud to eliminate points from areas you want to be masked.
Build the mesh.

Second create masks using the preliminary model:
Right click a photo.
Click on "Import Mask".
Select "Active chunk" and "From model".
Click on "OK" and masks will be generated.

Now you can align the masked photos, generate a new dense cloud, etc.

General / Re: Best buy camera and lens?
« on: August 19, 2014, 07:04:01 PM »
Keep in mind that unless the subject is relatively flat the lens aperture will usually be set to f5.6 or small (larger number) to increase depth of field. Differences in image quality between lenses are usually much less at smaller apertures. Also lenses with smaller maximum aperture generally cost significantly less then lenses with large maximum apertures, and the smaller maximum aperture lens may be sharper.

General / Re: Best buy camera and lens?
« on: August 15, 2014, 07:08:17 PM »
I have used the Canon 40mm extensively on a Canon T1i/500D (APSC sensor size) with excellent results in PhotoScan but I have not done any rigorous A-B testing comparing it to other lenses.

bmc130, the original poster, mentioned possibly using a Canon D70. I assume he means a Canon 70D which has an APCS size sensor. The 5D MarkIII he has been using has a "full" size sensor.

General / Re: Developing RAW to JPEG
« on: August 15, 2014, 06:54:07 PM »
Thanks David. Do you happen to know whether RawTherapee developing is 'lossless'?

I assume by "lossless" you mean no information in the image is lost by compression, etc. That depends on the output format, not on the software used.  JPEG always has some loss of information, even when quality is set to 100%. Higher JPEG quality results in less loss but larger files. Uncompressed TIFF is lossless but at the cost of considerably larger files. TIFF with LZW compression is lossless but I don't know if it works with PhotoScan.

All "development" software I've seen can output in both JPEG and uncompressed TIFF formats. I have been using uncompressed TIFF for PhotoScan but for a recent very large project I used JPEG with 100% quality to reduce the file size.

General / Re: Developing RAW to JPEG
« on: August 14, 2014, 02:44:03 AM »
"Developing" RAW files to JPEGs or TIFFs is generally a simple process, with the option of working with individual images or doing batch processing. Typically there are automatic options for the required settings. Camera which shoots RAW usually come with software to do the conversion. I also use Lightroom and Optics Pro. RawTherapee is free. There are numerous other software packages available.

General / Re: focal length
« on: August 12, 2014, 12:29:45 AM »
30mm equivalent focal length should be fine. I've used a range of lens from 16mm to 96mm equivalent focal length.

I had a similar problem with a long strip of photos. The photos taken with a camera/lens with relatively high distortion, and there was just enough overlap for the photos to process. No GCP's.

My hypothesis is the minimal overlap resulted in the PhotoScan lens correction being slightly in error, and accumulation of the error along the strip resulted in the curvature.

You may need more photos with more overlap.

General / Re: GPU processing during the modeling and settings
« on: July 30, 2014, 12:27:39 AM »
Current project has 250 to 750 photos per chunk. Medium setting for Create Dense Cloud results in 1 million to 7 million points per chunk, and takes considerably longer then Build Mesh.

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