One doubt about an equation in your paper

[TwiceMao]

In the formula (2) in your paper, I think $\varphi_{0}$ is not the phase angle mentioned in the main paper, but the azimuth angle of the surface normal. And why does the second component of the surface normal vector have a negative sign in front of it? Thank you for your answer.

[GCChen97]

Hi @TwiceMao , sorry for the late reply. For Q1, the phase angle is equal to the azimuth angle of the surface normal, up to the pi/2 ambiguity, in the OPA model. For Q2, the sign depends on the definition of the positive angle. In my definition, the positive angle is counter-clockwise.

[TwiceMao]

Thank you for your reply.