// 08.08.12 // 10.01.02 function X3=Zperspt(P) global FocusPoint EyePoint Tmp=P-FocusPoint; X1=Tmp(1); Y1=Tmp(2); Z1=Tmp(3); Tmp=EyePoint-FocusPoint; E1=Tmp(1); F1=Tmp(2); G1=Tmp(3); Ca=E1/sqrt(E1^2+F1^2); Sa=F1/sqrt(E1^2+F1^2); X2=X1*Ca+Y1*Sa; Y2=-X1*Sa+Y1*Ca; Z2=Z1; E2=E1*Ca+F1*Sa; F2=-E1*Sa+F1*Ca; G2=G1; Cb=E2/sqrt(E2^2+G2^2); Sb=G2/sqrt(E2^2+G2^2); X3=X2*Cb+Z2*Sb; endfunction