Exercise 1a: RTIBuilder

The software that we will be using in this chapter is called RTIBuilder and is provided by the Cultural Heritage Imaging Cooperation. It is free and (more or less) open access. So head over to their site and go to What we offer and Downloads. Direct Link!


On the next page, you can click on Process - RTIBuilder free software and choose your version (either PC or Mac) on the next page. Rightly, there is a warning that this is old software, but you can either ignore that or move on to the ReLight chapter. Start downloading! Install the package on your computer.

Attention for PCs: Make sure, that you install the RTIBuilder software in your root folder of your computer (C:\). Don't install it in a programs folder or anything. The RTIBuilder does not do very well with spaces or special characters. Make sure, that it is installed in something like: C:\RTIbuilder_v2_0_2\.

It might be, that your system tells you, that this file contains a virus. I installed this software a hundred times and am pretty sure, that it doesn't. Feel free to download and install it anyway. If you encounter problems with downloading, try another browser.

At least for PC, you also need Java 6 or higher, which you can get here. It is free for personal use, so please install that as well. If you have installed both software, you should be able to start the RTIBuilder, which you should find under RTIBuilder/RTIBuilder in your start menu (Windows). Please try it and have a look, if the software starts up.

PTM Fitter

The software works like this, but only offers the HSH Fitter, which is the algorithm with which the RTI gets calculated. This is fine, but there is another Fitter, the PTM Fitter, which is a little bit better and offers more possibilities with filters after the creation of the RTI. Please download this ZIP-File and unpack it into the Fitters-folder of your RTIBuilder installation. Normally you should find the folder under C:\RTIbuilderv202\Fitters\. If you unpack the ZIP, there should be two subfolders in the Fitters folder: HSHfitter and PTMFitter. In the PTMFitter folder, you'll find four files.

Building the RTI

Here, we explore the RTIBuilder software and have a step-by-step instruction on how to use it to create a RTI image. When you open the software, you will see the start screen, where you can enter a project name (no spaces), choose an operation sequence and start the process. Enter a suitable name for your project without using any spaces (1), select Highlight Based (PTM Fitter) (2) and click on the Start New Project-button (3). You have to be careful with your typing. Spaces and odd symbols don't go well with this software. If you have any problems, it is most likely, that this is due to a crooked path or filename.

In the next screen, we have to click the Open Folder button to open our folder with the images. RTIBuilder needs a certain file structure to work. For this reason, the images should be stored in a folder named jpeg-exports, which again is in a project folder. The folders cannot have any spaces in the name, therefore it is a good practice to store the project folder in the root folder of the hard drive (for example C:\Project_Name\jpeg-exports).

After RTIBuilder has loaded all the images (which can take a while), you can see them in the program. On the left (1) you have a preview window of the selected image (default is the first image) and on the right (2) you have the thumbnails of the complete set of images. On the lower left corner, you can enter some metadata (3). Basically you can write your name and the projects name in the appropriate fields. It is possible to add additional metadata for further information about the documenting process. You could record the used camera and lens or the length of the string you have used when creating the images and so on. You can find some further suggestions which kind of metadata to use on the following page: https://ianus-fdz.de/it-empfehlungen/forschungsmethoden/rti. For now, we leave it with our name and the projects name. You can click on the Next button (4).

In the next screen, we need to tell the software where in these images we positioned our sphere. In this version of the RTIBuilder, we only need to select one sphere, but on future versions, more spheres can be used. You can create a green rectangle like on the screenshot (1) by simply clicking with your mouse and dragging. Don't worry, you will be able to adjust that rectangle in a minute. Leave the process configuration on Black glossy ball (2). We have used silver ones, but as there is only an option for black and red, we will leave it on black. Press Add area (3) to define the area. The green rectangle will turn red. You can now adjust the rectangle by moving it with the little handles on the corners (1). Try to encompass the whole sphere and leave a little space around it. Don't make the rectangle too small. When you are happy, press the Detect Spheres button.

In the next screen you will see a green representation of your sphere with a red circle around it. The software tries its best to detect the sphere automatically, but most of the time we have to help a little. With the small handle in the middle of the sphere (1), we can move the red circle around. With the small handle on the right side (2) we can adjust the diameter. Try to be as exact as you can. As soon as you have moved the red circle, you have to save the new position and diameter via the Set New Center button (3). If the green representation doesn't work for you, you can switch to a normal representation by selecting the last thumbnail in the list of images on the right side (4). Again, after moving and scaling the red circle, you have to save the new position and diameter with the Set New Center button (3). When you are happy, proceed via the Next button (5).

On the next screen, you will see your sphere with the adjusted red circle around it. You can now simply press the Highlight Detection button. After a while, the software will show you the detected highlights by placing a very small red cross exactly in the middle of it (1). For the most part, RTIBuilder detects the highlights pretty well. It struggles with low light angles though. We therefore need to check every image and the detected highlight represented by the red cross. This is more of a problem with "handmade" RTIs and not so much with RTIs that where made with a closed dome. Open RTIs tends to reflect more than one highlight, while a closed dome prevents that. If you use a dataset from a handmade RTI, go through every image in the thumbnail list and check if the small red cross is exactly in the centre of the reflected flash on the sphere. If it is not, you can move the red cross with your mouse and save the new position with the Redefine Highlight button (2). When you have checked all images, proceed by clicking the Next button (3).

RTIBuilder is now nearly set up to start the fitting process. The only thing we need is to define a cropping frame. To do so, just click the checkbox besides Use crop. You can now define a frame around the object. Try to leave a little space around it (1). We do not need the spheres any more, we only want to see the object itself. On your version, it might be necessary to find the PTMFitter file first. To do so, click on the Find button (2) and navigate to the folder C:\RTIbuilderv202\Fitters\PTMFitter and select the PTMFitter.exe file. You can now simply press the Execute button (3).

After fitting is complete, you can navigate to your projects folder into the subfolder finished-files and double click the PTM file you just created. The RTIViewer application should open up and you can now see the result of your fitting process. Have fun!

This page was last edited on 2024-04-11 14:18

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This page was last edited on 2024-04-11 14:18

Sebastian Hageneuer
CC BY-NC-SA 4.0 Deed

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