Based on my question at here How to draw dashed arc of a circle behind pyramid?
I tried
\documentclass[border=2 mm,12pt,tikz]{standalone}
\usepackage{tikz,tikz-3dplot}
\usepackage{tkz-euclide}
\usetikzlibrary{intersections,calc,backgrounds}
\usepackage{fouriernc}
\tikzset{reverseclip/.style={insert path={(current bounding box.south west)rectangle
(current bounding box.north east)} }}
\begin{document}
\tdplotsetmaincoords{70}{290}
\begin{tikzpicture}[tdplot_main_coords,line join = round, line cap = round]
\pgfmathsetmacro\a{4*sqrt(2)/2}
\pgfmathsetmacro\h{2*\a*sqrt(2)/2}
% definitions
\path
coordinate (O) at (0,0,0)
coordinate(A) at (\a,0,0)
coordinate (B) at (0,\a,0)
coordinate (C) at (-\a,0,0)
coordinate (D) at (0,-\a,0)
coordinate (S) at (0,0,\h)
;
\draw [thick] (S) -- (B) -- (C) -- cycle;
\draw [thick] (S) -- (C) -- (D) -- cycle;
\draw[dashed,thick]
(A) -- (B) (A) -- (C) (B) -- (D) (S)--(A) (A)--(D) (S)--(O);
\begin{scope}
\path (O) circle ({\a});
\clip (S) -- (B) -- (C) -- (D) -- cycle [reverseclip];
\draw[very thick] (O) circle ({\a});
\end{scope}
\begin{scope}
\clip (S) -- (B) -- (C) -- (D) -- cycle;
\draw[dashed] (O) circle ({\a});
\end{scope}
\foreach \point/\position in {A/above,B/left,C/below,D/right,O/below,S/above}
{
\fill (\point) circle (1.8pt);
\node[\position=1.5pt] at (\point) {$\point$};
}
\end{tikzpicture}
\end{document}
How can I get full line of circle of this picture?