question on the DLT coefs

[Pauline Provini]

Dear all,

I am working with the XrayProject and I am wondering what are the
parameters saved in the _DLTcoefs.csv file, generated after the use of
the calibration cube.

I've seen it was possible to chose either 11 or 16 parameters but I
can't find exactly what they are in the MatLab code. I guess the
optical center coordinates, the focal distance and the enlargement
parameters must be there, but I am not sure about their order in the
file.

Thanks for your help!

Pauline

[Ty Hedrick]

Hi Pauline,

The _DLTcoefs.csv file should contain the 11 DLT parameters for each
camera, with column 1 corresponding to camera 1 and so forth. The XROMM
approach uses an explicit correction for arbitrary distortion with the
recorded meshgrid and associated UNDTFORM files, so there is no need to
use the 16 parameter DLT which includes some corrections for non-linear
radial distortion.

However, the DLT coefficients do not directly encode the physical camera
parameters such as focal length, optical center, and so forth even
though all the information is present and can be extracted. An example
conversion of DLT coefficients to physical parameters occurs in the
mayacam.m file in the XrayProject-2.0.0 bundle, so you could start there
if you need those parameters.

If you want to know more about DLT as used here, take a look at this
excellent overview:
http://www.kwon3d.com/theory/dlt/dlt.html

Hope that helps,
Ty Hedrick