Csdrhrt

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]

 pgfmathsetmacroa{4*sqrt(2)/2}

pgfmathsetmacroh{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?

This happens because at the moment you are using reverseclip the current bounding box is not large enough to fit a circle with the line width you are going to draw. In your picture the perhaps simplest fix is to draw the labels before drawing the circle.

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]

 pgfmathsetmacroa{4*sqrt(2)/2}

pgfmathsetmacroh{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);

 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) {$point$};

 }



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}





end{tikzpicture}

end{document}

Run with xelatex:

documentclass[pstricks,border=15pt]{standalone}

usepackage{pst-3dplot}%

begin{document}

begin{pspicture}[showgrid=false](-4,-2)(4,6)

psset{Alpha=30,Beta=15}

pstThreeDLine[arrows=*-*,linestyle=dashed](-2,-2,0)(0,0,5)

pstThreeDLine[arrows=*-*](2,-2,0)(0,0,5)

pstThreeDLine[arrows=*-*](-2,2,0)(0,0,5)

pstThreeDLine[arrows=*-*](2,2,0)(0,0,5)

pstThreeDLine(2,-2,0)(2,2,0)(-2,2,0)

pstThreeDLine[linestyle=dashed](2,-2,0)(-2,-2,0)(-2,2,0)(2,-2,0)

pstThreeDLine[linestyle=dashed](-2,-2,0)(2,2,0)

pstThreeDLine[linestyle=dashed,arrows=*-](0,0,0)(0,0,5)

pstThreeDEllipse[linestyle=dashed](0,0,0)(2,2,0)(-2,2,0)

pstThreeDEllipse[beginAngle=-90,endAngle=140,linewidth=1.5pt](0,0,0)(2,2,0)(-2,2,0)

pstThreeDPut(-2.4,-2.2,0.2){large$A$}

pstThreeDPut(2.2,-2.2,0.2){large$B$}

pstThreeDPut(2.4,2.2,-0.2){large$C$}

pstThreeDPut(-2.4,2.2,0.2){large$D$}

pstThreeDPut(-0.2,0,-0.2){large$O$}

pstThreeDPut(0,0,5.3){large$S$}

end{pspicture}

end{document}