Angular to reciprocal coordinates

Transformation (θ₁, θ₂)→(Q_x, Q_z). Note: it uses the global value |||VelkeK| = $\displaystyle {\frac{{2\pi}}{{\lambda}}}$ . */

void QxQz_from_Theta1Theta2 ( double& Qx, double& Qz, double Theta1, double Theta2 ) if (RecSpaceNearOriginApprox) Qz = VelkeK * ( Theta1 + Theta2 ); //+ Q_z = K(θ₁ + θ₂) Qx = Qz * ( Theta1 - Theta2 ) /2; //+ Q_x = ${\frac{K}{2}}$ (θ₁² - θ₂²) else Qz = VelkeK * ( sin(Theta2)+sin(Theta1) ); //+ Q_z = K(sinθ₁ + sinθ₂) Qx = VelkeK * ( cos(Theta2)-cos(Theta1) ); //+ Q_x = K(cosθ₁ - cosθ₂)

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