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leszekp

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Posts posted by leszekp


  1. Windows Defender is the standard anti-virus program that comes with Windows 10. It will show up as a shield icon in the trayicon area. Double-click on it, select "Virus & threat protection => Virus & threat protection settings => Manage settings => Exclusions => Manage exclusions". Add the RTI_Builder folder (usually in the root directory on the C- drive). This should fix the problems. You may need to reinstall RTIBuilder.

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  2. Yes, you can use a studio light at different angles. If you can, remove any diffuser or reflector, leaving just the bulb. As long as the sphere is visible in the photograph, and isn't too far away from the inscription you're trying to read, you can put it anywhere convenient. If on top, place it near the edge so that the highlight won't be blocked by the tombstone.


  3. I have regularly had problems with the standard PTM fitter on Windows for images larger than 24 megapixels; it usually crashes. For all my PTM processing, I've switched over to using the new ptmfitter from Custom Imaging, available at https://custom-imaging.co.uk/. It can handle images up to 100 megapixels in size, and as a bonus it's a lot faster than the original HP fitter. On the downside, it won't work with RTIBuilder, so you'll need to create an lp file with RTIBuilder, and then use that with the new ptmfitter in command line mode.


  4. If you're going to do SfM work, I'd recommend at least 32 GB of RAM, and as much as you can afford (though most motherboards can't take more than 64 GB). SSD drive for the boot and main work drive, at least 256 GB; regular hard drive for longer-term storage is fine. Definitely recommend nVidia for the graphics card, and get the fastest one you can afford; video RAM is not as important. Not sure you'll be able to upgrade your ToughBook, though.


  5. Haven't used PhotoModeler, so can't speak about it. Did the trial version of Pix4D, and results looked good, although the trial version didn't export in the highest resolution. I've mainly worked with Photoscan, both Standard and Pro versions, and have been very satisfied with it. Have done a number of archaeological drone projects with high-accuracy GCPs using RTKGPS, and have been very happy with the results in terms of accuracy.

     

    BTW, Photoscan is dead - it's now called MetaShape.


  6. Somewhere online there used to be a description of the ptm format, but that appears to have disappeared. It should be described in the original Malzbender paper about PTM. Don't know if I've ever seen anything comparable for the rti format, but the original paper about HSH fitting should give you some information. You might contact CHI directly for the source code for the hsh fitter, and that should give you information about the storage format for the rti files.

    Not sure exactly what kind of useful information you expect to get from the files. They just store the fitting coefficients for every pixel (along with the RGB date) that's used to calculate normals, both of which are used by the viewer to display the image and the effects of changing the lighting angle.


  7. You might also try stopping down even further to F11, to get a better depth of field. The other issue is whether the skull has enough details on it for Photoscan to be able to match points between different photos. If not, you might try shooting RAW, then increasing contrast/clarity in the photos to accentuate whatever details are present.


  8. For lithics, I use the normals mode, then manipulate the RGB channels individually for maximum contrast. Convert to grayscale, do some more advanced contrast work (clarity/CLAHE), sharpen it up, and you get a fantastic image of the flake scars on the stone tool, better than any hand drawing.


  9. Running the 3W LEDs continuously is definitely a bad idea when there's no heat sink. The solder melting point is less than 200C. They only need to be on long enough to take your photo, which shouldn't be more than a few seconds. While many of these are rated up to 1A, the usual nominal operating current is 700mA, at which current level they will stay quite a bit cooler. Intensity is a bit lower, and the exposure time will be slightly longer, but it's not going to be a huge different (a few tenths of a second).


  10. I had the same thought a few years ago, but decided that it didn't make sense. You're fitting a curve to the (primarily) Lambertian lighting scattering at every point based on the lighting angle. If you change the lighting intensity with angle, you'll skew the lighting curve to fit to those higher intensities, which will introduce errors.

    Shadows are areas where the main light source is blocked, so any signal from those areas is a result of scattered light within the dome, which doesn't really offer you any useful signal for curve fitting.

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  11. This is a useful rule-of-thumb, but I've found that you can sometimes stretch this a bit. I just did RTI on a 7" long Mayan lithic blade inside a dome with a 9" light to object distance, and got a more than acceptable photo out of it (with a bit of work in Photoshop).

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