Reflective Diffraction Grating

Question

I have collimated light coming in to a Diffraction Grating (object material set to mirror). It is oriented at Lithrow angle such that green (for example) reflects right back along the optical axis. The Pitch axis is set to my lithrow angle. In this configuration I should be able to Yaw the grating, steering the rays like a mirror. However, there are 2 issues
1) If my yaw angle is 4 deg, for example, it does not steer by 8 degrees as expected
2) My 'blue' and 'red' wavelengths rotate around the 'green' wavelength as I yaw.
If I 'clock' the grating (z rotation) then I can derotate the rotation. For some reason, in order to steer, unclocked by 8 degrees, instead of a yaw of 4, I need a yaw of like 2.5, and a clock of 2.5 as well.
Has anyone experienced something similar. This is odd behavior. The yaw should simply steer it like a mirror, if the the grating lines are oriented in the pitch axis
 
Thank you

Berta.Bernad · Accepted Answer

Hi Jacob,Glad that you got it to work. In Non-Sequential, if you expand the Properties of the object and go to the Type tab, you can check or uncheck 'Use Global XYZ Rotation Order'. If checked, the rotation convention for object tilts is to first rotate about the X axis, then the Y axis, then the Z axis. If unchecked, the rotations are done about the Z axis, then the Y axis, then the X axis. This latter ZYX convention is what a sequential coordinate break surface does if the order flag is zero.

jacob.begis@centauricorp.com · Answer

So, I did the same setup in Sequential mode and got it to work.

The issue is the order of the rotations. Whether x-rot, or y-rot is performed first. It seems like there is no way to change the order in non-sequential.

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