Processing .rti or .ptm files?

[Rubén Parrilla]

Hi everybody!

 

First, sorry for my english. I'm a Archaeology student from Southern Spain. At this moment, i'm investigating how to use differents computational methods in the research of small objects.

 

CHI and his project was an amazing discovery to me. Thanks to you all.

 

The question is simple. ¿Is there a way to export .rti or .ptm files? work with the files in other softwares in the way to get meshes for Blender for example.

 

Thanks.

[leszekp]

You can in principle reconstruct a 3D surface using normals calculated from the PTM and RTI files. Here's a link to a paper where they did that (see Figure 11):

 

http://palaeo-electronica.org/2002_1/fossils/issue1_02.htm

 

I don't believe the software to do this has been released, so you'd have to write it yourself.

[cdschroer]

Dear Ruben -

 

Maybe you already understand this, but for the forum followers I will provide a short explanation of RTI data and how it is different from 3D model data.

 

An RTI does not include x,y,z coordinates in space like a 3D model.  It does include color and shape information, but that information is stored as color and the mathematical description of a surface normal per pixel. Some people refer to this as 2 1/2 D. There is an explanation of surface normals on the RTI technology page at CHI.  And also there are links there to papers, such as from Tom Malzbender on PTM that has all the math. (look in the right hand gray column for the papers)

 

Some groups have worked with normal maps derived from the RTI files (and I use RTI to cover both ptm and rti file types - RTI is this class of imaging, ptm was the first type of RTI and was released in 2001)  I am happy to report that the new RTIViewer 1.1 release will include the ability to see the normal map as a false color visualization, and also to export the normal maps. Normal maps are different than RTI files in that the X, Y, and Z components of the normal value at each pixel are represented as red, green, and blue, respectively.  There is no color information or luminance or specularity - they are just a way to represent the normal direction.  The RTI file format contains this additional information.  From a normal map there are ways to convert to a 3D surface.  There are also some problems with doing that conversion, and errors can be introduced. This is impacted by the accuracy of the normal data.  Many factors in how the RTI data was captured and processed affect the normal accuracy, which would not be noticeable in viewing an RTI in an interactive viewer.   Converting a normal map to a 3D surface can be useful for comparing RTI data shot at different times, or with results generated by different algorithms. If you really want to get a 3D model, we would recommend using photogrammetry (or possibly structured light).

 

Carla

 

PS:  I know I have been saying RTIViewer 1.1 will be out "soon" for a few months now.  We are really, really close at this point, just tidying up a few last minute items and finalizing the User Guide.  I do apologize for the delay in getting it completed.  We had a very tiny budget for this project and a lot of the work ended up being done as volunteer efforts. There was also a lot of travel over the summer by members of the team.