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This does it. Thanks very much. My error was in mis-understanding sequence of operations.

Using OpenCV 3.2 for a local positioning system utilizing aruco.

Have successfully extracted 3d angles/matrices between camera and identified markers. But I also need to calculate the angle to the camera caused by translation of the marker in x and y. Using typical methods in OpenCV, it is straightforward to get this translation vector.

But I am stuck on how to straightforwardly go from the translation vector to angle of incidence.

I have searched/read widely, but have not found any commentary on this. I am not a 3d expert by any means and it is more than possible I have just overlooked something.

My own instinct at this point is to simply translate 0, 0, 0 in model coords to a camera location, and estimate the angle of incidence geometrically. There are some obvious problems with this, and I suspect it will be less than satisfactory.

So - my question is: Is there a straightforward way of going from the translation vector returned by methods like solvePnP() or estimatePoseSingleMarkers() to the angle of incidence to the camera caused by the translation? This is NOT the angle of pose - these come (reasonably) directly from these functions - but these angles not reflect changes in the angle of incidence due to the translation - the incorporate only the actual rotation of detected object.

Any help greatly appreciated,

Seth

I have solved the problem - am adding answer to original question text.

Problem Solved: I resolved this by also building the videoio module. This module is not listed in the aruco CMakeLists.txt. However, inspection of the source of some of the samples made clear that it was needed. Adding it to the build caused the aruco samples to be built. For those interested, the executables were put in the bin directory of the build directory, as has been true in the past. And as usual, make install does NOT install them anywhere. Thanks for all the suggestions.

I did try issuing cmake in the various samples folders - did not help. Either just ran the overall opencv config, or did nothing complaining that it could not find either the source or other relevant files

to answer the questions: no samples are built that I can find. I usually name the build directory 'release' and in the past the samples executables have been in 'opencv/release/bin'. This time it does not even make a bin. I did look inside the main samples folder, the aruco samples folder, the apps folder, and a few other places. No luck.

Can you give me more input on which cmake output files would be useful to see? I am not a ccmake/cmake/make maven.

added more info - hope it helps

I have expanded the info here - as requested.

I am a long time user of OpenCV. For the past several months been working with aruco on a very small embedded system using Ubuntu 15.10 and OpenCV 3.1/2. My development cycle starts on a large Intel system running Ubuntu 16.04. I develop the code on this, then copy the source to the armv7l/Ubuntu 15.10 embedded system, and recompile.

Size is limited on the embedded system, and I have successfully built and used aruco on a minimum OpenCV build (aruco, core, highui, imgproc, img_codecs, calib3d, features2d, flann and ml). The resulting static libs link and function properly with a small multi-threaded system that uses aruco for local position. This works both on the large Ubuntu 16.04 machine, and the embedded Ubuntu 15.10 one.

My problem is that I want to use the examples that come with aruco for marker creation and calibration. I only need this on the larger Intel/Ubuntu 16.04 system. I did not have any problem with this on 3.1. I simply used ccmake to set BUILD_EXAMPLES to ON, and recompiled.

But this does not seem to work any more. As far as I can tell, the system does not even try to compile the examples.

I am not getting any errors. I have tried building a fuller version of opencv - though not absolutely everything. About the only odd thing in my setup is that I limit it to static libs. So I tried it with shared libs with no change in results.

I have completely torn out opencv and restarted from new git clones. I have looked on this forum, and more broadly, for hints and have not discovered anything.

I can undoubtedly figure out how to compile the couple of tools I need, since the code is in the tree. But, I am thoughtful that it simply will not build any examples.

So - anybody have any thoughts as to what could be going on?

thanks much

Problem Solved: I resolved this by also building the videoio module. This module is not listed in the aruco CMakeLists.txt. However, inspection of the source of some of the samples made clear that it was needed. Adding it to the build caused the aruco samples to be built. For those interested, the executables were put in the bin directory of the build directory, as has been true in the past. And as usual, make install does NOT install them anywhere. Thanks for all the suggestions.

Tetragramm - thanks. perfect.

I regular rebuild opencv for a variety of tiny embedded platforms. As a result I constantly find myself configuring and reconfiguring to get things to build - because I cannot find a determinative reference that tells me how each module depends on other modules.

A good example is my current challenge - getting a minimum build with aruco on small arm system (nanoPi NEO Air - an awesome little beast). Small size is important - but I am finding that as I cut things back, at a certain point it no longer even tries to build anything in opencv_contrib. No errors - just does not attempt to build aruco, or anything else in contrib.

I am sure you can imagine the headache, as I guess my way towards a larger footprint that will finally build.

Anybody got any ideas? Does such a reference exist? Is it implied somewhere in the docs that I have just missed? Is it buried make files?

thanks!