Camera in marker coordinates

[bart_kevelham]

Hi all,

I am new to ARToolkit and I'm trying to get the coordinates of the camera (it's location and orientation) in markerspace coordinates. That is, with z pointing up from the marker. Now, I have been able to transform the result of arGetTransMat in such a way that I do get the correct location, but the orientation isn't correct.
For some reason, when I hold the camera at a fixed position and do a roll, the results I get would suggest a roll in the other direction. (Translations of the camera are handled correctly). I have followed the following approach to get from Markerposition in cameraspace to camera in markerspace:

1. negate the translation in the matrix returned by arGetTransMat
2. transpose the rotation in the matrix returned by arGetTransMat

Am I missing something? I have seen several discussions on this issue but (as far as I could tell) no real solution. If I overlooked it, I'm sorry and a link would suffice.

Kind regards,

Bart

p.s. nice work on the new website. Looks really good and instructive.

[bart_kevelham]

Nobody who can give any pointers? So of you must have done it before. I must be overlooking something. All help is welcome.

Bart

[philip_lamb]

That procedure is correct.. are you sure you're interpreting your results correctly? I don't mean to sound facetious, but perhaps put your eye down near the marker, rotate the camera, and check that the sense of the rotation is what you expect.

See also http://www.hitl.washington.edu/artoolkit/documentation/cs.htm

[bart_kevelham]

Okay, if that is a correct approach then the error must lie somewhere else. Let me ask this:

How does ARToolkit expect to get his image. I mean, where is the origin (0,0) of an image supposed to lie? Left top, or left bottom?

And any other "have you thought of this, you fool" type of comments are welcome as well. ;)

Thanks in advance,

Bart

[J.Sch?ning]

I think left bottom.
Cheers