Is the cartesian view looking at the detectors from the sample position?

[jhektor]

I have a very fundamental question. In the Cartesian view, are we looking at the detectors from the sample position along the beam, or are we looking from behind the detectors along the positive z-axis?

[psavery]

I believe it is looking from (0, 0, 0) in hexrd lab coordinates, which is often the sample position (although the sample could technically be located elsewhere), and the direction is along the beam if the azimuth and polar_angle are both 90 degrees, but those can be changed as well.

@saransh13 can you clarify?

[donald-e-boyce]

See transforms.pdf.

I believe the viewpoint is from the origin in the detector frame, which is the "centroid of the active surface." Also note that the beam is in the negative z-direction, so we are looking at it from the front, not the back.