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Testae

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Testae last won the day on June 6 2016

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  1. Hello everybody, as RTI is more and more used in various fields, I felt that it would be of great use if users would somehow standardize the way they are displaying their images created by means of RTI. Here is a suggestion. I introduced and used this standard for my master's thesis on the RTI of transparent materials (see https://www.dropbox.com/s/8rjl3tmq1jfswtz/Dittus_RTI-transparenter-Materialien.pdf?dl=0 pp. 66/67) and it is to my knowledge also used in the conservation course of the State Academy of Arts and Design Stuttgart since when publishing RTI images. But of course this is just a suggestion and up to any discussion. However I think it helps especially for two reasons: first of all an image becomes recognizable as RTI-generated as opposed to being a 'traditional' photograph at first glance. And additionally it provides all important information on where the digital light is coming from and what filters were used. So here are the key points: - Insert green ‘light controller‘ (screenshot from the viewer) - Insert scale - Mention the rendering mode and, where the mode is available for both algorithms, the computing algorithm in the caption - Mention light coordinates as shown in the viewer in the caption - If the image needs to be rotated, insert the light controller prior to rotating and mention the rotation angle in the caption. Here is one example caption for the attached image: Plastic foil with kinks and dust; SE mode (HSH), X -0,37 Y -,014. I would love to learn what you think of the idea! Best, Alex
  2. leszekp, this is my website, glad you found it... As mentioned above I worked on the topic of documenting glass, transparent polymers and other transparent objects with RTI in my Master's thesis. I will soon have it ready to hand it out to anybody who is interested in the topic (just some little layout corrections etc.) but in the meantime you may want to check out this poster from a conference in Berlin: https://de.dariah.eu/documents/10180/472725/48_Dittus-RTI_transparenter_Materialien_Poster.pdf/2b300533-d145-4dc5-b424-4411dde85551 It is in German I am afraid, but you can see in the pictures how RTI can improve the documentation of cracks, bubbles, engravings etc.
  3. Thanks a lot for your replies and links everybody! Especially Tom's explanation helped me a lot in understanding why these phenomenon occurs. I think it is very important to know that there is a chance of these errors to occur so one has that in mind when it comes to looking at RTI files of paintings and other polychrome surfaces. For the transparent materials: I discovered the possibility of using RTIs on transparent materials "accidently" when looking at a RTI of a painted glass bottle. In the areas where there was nothing else but glass some fine scratches showed up in the specular enhancement mode that were nearly invisible when looking at the glass directly let alone in photos of the object. After some other tests I can say that in some cases it is possible to show details of structures on or in transparent materials using RTI better than this would be possible using plain photography. Based on what I found out so far the most important thing is to use plain monochromatic background with no structure, just as leszekp mentioned. If this background is black, nearly all the light is reflected by the transparent object's surfaces. And this helps to show details on and in the glass or transparent polymer. Of course the result does not show one surface of the object but all surfaces (so if you compare the information in a regular RTI to a photo, the information in a RTI from a transparent object is somehow rather an x-ray *wink* ). But every structure that reflects the light does show up, e.g. surface irregularities, scratches, bubbles and so on. So I think if one understands where the information one gets with this data is coming from (i.e. not the first surface of the object but every reflecting surface plus there is an interaction of various reflections from the different surfaces) RTI is quite a helpful tool when it comes to investigating transparent objects. Not because it accurately visualizes everything but because it shows things that would otherwise remain barely visible. Here are some examples of polymer materials (not the best results I achieved so far but I just had that file sitting around): First of all a pet packing. Although there are some errors a good amount of the surface normals looks quite "possible" in my opinion. This is a transparent PE bag. As you can see, the SE-mode clearly helps to show the surfaces structure of the wrinkled plastic. Green transparent plastic. The scratches appear more obvious in the SE-Mode (please note that in this case a white background was used. A black background would result in better images with clearer surface normals. Last one is a PS box. Here the SE-mode can help to show the fine scratches in the surface, while in the default mode especially the rough and big scratches are visible. I would love to hear your opinions on these. Alex
  4. Thank you for your interesting thoughts on that Taylor. I am afraid that I will not find the time to look into that topic more deeply as this is not a big aspect of my thesis but I gave it a try today with different printed papers (please see pictures below). One is a page from a book (lower left), the other is a journal's cover (lower right). I printed a lorem-ipsum using an ink jet printer (upper right) and a laser printer (upper left) and also wrote on the paper with a felt tip and a pencil. All of these do show up in the normals visualization and accordingly also in the specular enhancement mode. This of course should not happen as there is no change of the paper's surface normals just by printing on it. So I assume that color contrasts have a huge effect on the surface normals. This also carries a great danger of misinterpreting RTI-Files. I had some cases where I became very suspicious because for example the outlines of a painting looked very elevated in specular enhancement although they did not appear like that in the paint layer itself. One of the best "real life examples" was an RTI of an reverse glass painting I recorded lately (I hope this is the right term for those kind of paintings that are created on a glass plate instead of a canvas). So the pictures were taken through the glass depicting the bottom side of the paint layer. Thus the paint layer should have been absolutely flat and in respect of that one would expect a rather monochrome blue for the normal visualization. However the whole painting showed up in the normal map and appeared to have a three dimensional paint layer when viewing the file in SE-mode. So it looks to me as if I can not really trust the normals created from surface areas with various colors close to one-another. Is there an explanation for patterns only resulting from a color contrast to show up in the surface normal visualization? Default SE normals
  5. Hello everybody, at the moment I am working on my master's thesis with a RTI-related topic ("Reflectance Transformation Imaging of Transparent Materials") and therefore I of course have to think a lot about the results and information one can obtain with this technique. I came across this earlier but in the last days the following question crossed my mind again and again, especially as the new viewer is able to generate a normal map that can be viewed and examined: So imagine if you have a plain paper with text on it. Pictures are taken with a regular camera and you do your best lighting the whole thing equally or even use some kind of dome. And then you check the normals visualization in the viewer. What you will end up is a display of the paper, its wrinkles (if there are any) and structure (if your camera is good enough). But what you will also see is the text printed onto the paper. But the paint would have sunk into the paper when you printed it. And even if not, it should not build normals in the way they are visualized in the normal map. So this shows that the color sometimes affects the normals in quite anextensive way. Question is: If this is obviously the case, how do I know that an RTI of a painting for example really shows the paint layers and not the differences in color darkness in the normal visualization and the specular enhancement? I discussed the normals-and-color-problem a while ago with George already and then thought that it was due to the fact that I did not use a dome. But now I built a dome and especially contrasts of bright and dark colors still lead to the described issues. So I wonder what to think about this phenomenon? Best, Alex
  6. Testae

    New Viewer

    Dear RTI-Team, I would like to tell you how grateful I am for the new version of the RTI-Viewer. It is so helpful to have all these settings as actual values. This makes the pictures reproducible and thus is a giant leap in terms of a standardized use of the technique. I also love the fact that it is now possible to view and export the normal map. You did an awesome job there! Alex
  7. George, thank you for taking time to think about that issue. Um... what do you mean by "R"? Honestly this topic appears to be quite complicated to me. But it might just be all these formulas that frighten me off. Well, anyway, here is the blend-sphere of the PTM used for the normal map I posted above. All of my RTIs are done with a hand held lamp so the light patterns are rather irregular. Here are specular enhancement images, normal maps and blend-spheres of two other RTIs we did lately. On the scale the same phenomenon occurred again. If you PM me your email address I could also put the original pictures into a dropbox folder for you to experiment with. The article is very interesting and the results look really promising. When googling for it, it seemed like the PS method can also be used to generate real 3D data. Did I get that right? I guess this would be awesome as it would mean that two datasets recorded at different times (e.g. before and after a loan) from the same object could be adjusted and compared even if the object was not recorded from exactly the same position. Alex
  8. Hello, I am a conservation student and came across RTI about one year ago. Being immediately fascinated by the possibilities and easy processing I told a lot of my fellow students and professors about it. To my surprise none of them ever heard about it before. But I was asked to change that by giving a presentation on the technique. I am very happy to do that as I think it is absolutely necessary to know how to make an RTI as it is such an easy method to find out more about the objects we are working with. (Sorry, just a quick introduction because I am new to this forum ) I was experimenting a lot with RTIs and already used them for various problems. I was so happy to find this post as I was desperately searching for a way to extract normal maps from the files I created. I was experimenting with various things and came across the need for a normal map again and again. For example I tried to compare mockups before and after changing the relative humidity or scratching the surface using RTIs and Photoshop filters. What I always found curious was that for example the printed letters and dark checkers on the scale or any area with high contrasts appeared to be "higher" although I could not imagine that the tiny amount of ink on the paper would be detected especially if one bears in mind the size of the area covered in the image (I am just not able to imagine the resolution to be THAT good). But after reading this post and extracting the normals maps from the PTM-viewer I saw that the phenomenon already occurs in these. So I am a bit confused: Are the high areas really "higher" or facing in an other direction to be more precise? Or is it not possible to completely "separate" the surface information from the brightness of the scale, writing and the color card (or the object of course)? Thanks, Alex PS: Sorry if I do not know all the proper expressions. I hope you understand what I am wondering about anyway
  9. Tom, thank you so much for this info! I was not able to get the PTM Fitter running (even manually changing every file name did not work for some reason). But with your solution creating the files became a breeze! So thank you once again! Best, Alex
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