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leszekp

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Everything posted by leszekp

  1. I have Windows 10, and RTIBuilder runs without problems. Might be a Java-related issue. Check to make sure you have the latest version of Java installed on your system.
  2. About 3 weeks ago, I did a presentation at the Society For American Archaeology conference in San Francisco, titled "Documentation Of Lithic Artifacts Using An Inexpensive Reflectance Transformation Imaging System". I've just put an extended video version of that talk online at a website I've put together. It covers not just lithic artifact imaging with RTI, but also a field-ready portable RTI system I designed and constructed, and some experiments with converting RTI data into 3D models. The site also contains links to both RTI data files and 3D ply files for lithic artifacts, to view and download. Hope you find it interesting.
  3. z appears to be mapped to values of 0 to 255 corresponding to -1 to 1, but only values of 128 and above are used for normal colors, since z is never down into the screen. The B value in all normals images I've looked at ranges from 128 to 255.
  4. I had the idea of calculating the angle of a surface point from the normals picture using the RGB values. But when I assumed a normalized value for RGB to xyz, I was getting an angle far steeper than what was actually present on the artifact. Comparing normals colors on the artifact with the colored "sphere" in your post (and in the RTIViewer manual), I saw the same thing - the colors on the normals pic corresponded to angles far steeper than reality. Did some playing around with the data, and found out that if I divided the color values for R and G (corresponding to x and y) by two, then tried calculating the angles with the new values for normals, the values appeared to be correct. Here's the normals-colored sphere from the viewer manual, which does reflect a linear mapping of normals to color: And here's that sphere with the x and y values multiplied by 2: I'm guessing that the non-uniformities come from working with original jpg data; I may try and fix this at some point. The colors that correspond to various angles on the sphere now match up quite well to the colors on the artifact that I was observing. You actually want a steeper color gradient like this to pull out details, since it will accentuate surface curvatures to a greater degree than a one to one mapping of xy normals to RG colors. I've been getting some interesting and useful results on lithic artifacts using a -1 to 1 normals mapping, and other manipulations of the normals data; time permitting, I may show some of these at my SAA presentation next week.
  5. Sorry, I wasn't clear. In the post, you say "It is common to represent normal fields through false color visualization, where the x, y, and z coordinates are mapped to RGB: red, green and blue, respectively." The z coordinate will always be positive, and could be mapped directly to the blue value of RGB (just multiply by 255). But the x and y values can be both positive and negative, and you can only have positive numbers for the R and G values. So, you have to somehow re-map the x and y coordinates of the normal vector so that they can be converted into positive RGB values (and remap the z vector the same way). One possible mapping method might be to divide the vector values by 2, add 0.5, then multiply the result by 255 to get the corresponding RGB values for the normals image (R for the x-vector, G for the y-vector, B for the z-vector). This approach ensures that the RGB values will always be positive. My question was about the specific mapping mode used in RTIViewer to convert the x, y and z components of the normals vector into R, G and B values in the normals visualization.
  6. Does anyone know, what is the exact mapping of the x,y,z normal vector parameters to the R,G,B colors displayed in Normal mode? Tried to figure this out from the source code, but my knowledge of C++ is far too weak to decode that.
  7. Thanks for the link, Testae - look forward to your thesis (and trying to revive my grade-school German). And congratulations on your award!
  8. Here's someone who's using RTI to document cracks, scratches and bubbles in transparent glass bottles. Original website (in German): http://www.recad.de/Dokumentation/dokumentation.html Googlefied into English: https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fwww.recad.de%2FDokumentation%2Fdokumentation.html&edit-text=&act=url
  9. Probably the simplest way is to use a small reflective sphere in conjunction with the RTIBuilder software to generate an lp file. If you include the sphere in the photo along with the fossil, you could use RTIBuilder every time to generate both the lp file and the ptm/rti datasets. However, if you always take the photos in the exact same lighting sequence, you could generate a single lp file, and then use that as a template for future photosets. Check the RTIBuilder manual for more info.
  10. You might try re-installing the previous graphic card, then downloading new drivers directly from the chipset manufacturer (usually nVidia or Radeon/AMD). Windows update doesn't always include the best possible driver for your graphic card, so using the manufacturer's driver might fix the problem.
  11. Since the camera is fixed/static, you don't have to worry too much about blurring from long exposures. I have no experience with IR RTI. Here's a link to a recent presentation by Kathryn Piquette, where she used IR-RTI on Herculaneum papyri: http://www.slideshare.net/UCLDH/piquette-ucldh-seminar20141203forweb I think the University Of Southampton is also working with IR-RTI, but couldn't find a reference.
  12. Good question, and I don't know the answer. I've seen domes with higher angles, and my dome has a row of lights slightly outside that range (72 degrees) without any apparent ill effects. Perhaps this is just for Highlight-RTI? Maybe Carla or Marlin can chime in with an explanation.
  13. Typically done with a custom electronic control system that turns each LED on and off in sequence, triggering the camera shutter in sync through a remote control. You could also do it manually, powering up the LED and firing the shutter by hand.
  14. Incandescent has more output in IR than a standard LED, but LED efficiency is much higher, so if you'll primarily be working in the visible LED may be a better choice. Not sure what you mean by "right exposition at different aperture". If you mean exposure, you want all the lights to have the same intensity, and take all the photographs at a constant aperture and shutter speed to maintain the same exposure parameters for every photo.
  15. Seems like everyone who builds their own system designs their own controller, and writes their own software for it. That's what I did.
  16. Try this: http://annystudio.com/software/jpeglosslessrotator/ Seems to work fine for me. Has built-in Windows shell integration, so you can select multiple photos in a folder, right-click on and losslessly rotate them left or right. Doesn't affect the EXIF data.
  17. Just stumbled across this: http://www.adamcrume.com/blog/archive/2012/03/02/rti-viewer-on-github From the post and the date of the source files, looks like it's a port of an older version of RTIViewer to Android. No apk to install that I can find, but if there are any Android programmers out there, it should be possible to compile such a viewer based on the source files at GitHub.
  18. While I haven't imaged any fully transparent items (like glass bottles), I've had some success with semi-transparent material, specifically projectile points knapped out of semi-transparent obsidian. At a bare minimum, you need to have a uniformly-colored background material, preferably one with little to no texture.Here are links to three photos. First is a standard photo of the item against a photo scale, lit from overhead, where the scale is visible through the artifact. The second shows the normals view derived from the 2nd-order RTI, and the scale is still visible through and around the artifact. The third photo is a 2nd-order normals image where the artifact was on a more uniformly-colored background. Each small division is 1 mm.
  19. http://ydc2.yale.edu/news/2014/04/25/mirador-rti-viewer-demonstration
  20. The Inscriptifact Viewer has the ability to light an object from two directions at the same time, as well as adjust the lighting intensity independently for both sources. It's Java, though, so there may be issues on the Mac.
  21. I put together a fully-automated dome system (18" diameter) for about $500 in parts/tools, including the stand and sample stage (but not including the camera); requires some sweat equity. Current power supply limits you to 1W LEDs maximum power, which in turn limits the dome size to about 24" without the exposure times becoming unreasonably long. I'm working on higher-power drive electronics that could increase that to 3W, which would allow domes up to a meter in size (or shorter exposure times for smaller domes). While I can get usable results for samples 6-9" in size in my 18" dome, best results are for 4.5" and smaller, which fortunately covers the vast majority of artifacts I need to image.
  22. http://vcg.isti.cnr.it/~palma/dokuwiki/doku.php?id=research Haven't done more than a cursory look at it. Limited viewing options (no specular or normals, for example).
  23. The approach you discuss is very similar to the styrofoam dome system featured on this page: http://www.hpl.hp.com/research/ptm/MakingPtmNew.htm If you're worried about scattered light, you can always spray-paint the interior with flat/matte black paint to minimize this; that's what I used on my dome, and it works fine.
  24. What antivirus service do you use? Many of these programs use proprietary "heuristic" algorithms, where they rely on suspicious software "patterns" in addition to antivirus definitions, and I suspect that's what is happening here. I've had the same thing happen to a software program of mine; I had to submit it as a false positive to the antivirus service, and wait for them to fix the problem. Be prepared to have them tell you it's your fault.
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