How to draw a circle (sphere) passing through four points?












1















I am trying to draw a circle (sphere) passing through four points B, C, E, F like this picture enter image description here



I tried with tikz-3dplot and my code



documentclass[border=3mm,12pt]{standalone}
usepackage{fouriernc}
usepackage{tikz,tikz-3dplot}
usepackage{tkz-euclide}
usetkzobj{all}

usetikzlibrary{intersections,calc,backgrounds}

begin{document}

tdplotsetmaincoords{70}{110}
%tdplotsetmaincoords{80}{100}
begin{tikzpicture}[tdplot_main_coords,scale=1.5]
pgfmathsetmacroa{3}
pgfmathsetmacrob{4}
pgfmathsetmacroh{5}

% definitions
path
coordinate(A) at (0,0,0)
coordinate (B) at (a,0,0)
coordinate (C) at (0,b,0)
coordinate (S) at (0,0,h)
coordinate (E) at ({a*h^2/(a*a + h*h)},0,{(a*a*h)/(a*a + h*h)})
coordinate (F) at (0,{(b*h*h)/(b*b + h*h)},{(b*b*h)/(b*b + h*h)});
draw[dashed,thick]
(A) -- (B) (A) -- (C) (A) -- (E) (S)--(A) (F)--(A);
draw[thick]
(S) -- (B) -- (C) -- cycle;
draw[thick]
(F) -- (B) (C)--(E) (F)--(E);
tkzMarkRightAngle(S,E,A);
tkzMarkRightAngle(S,F,A);

foreach point/position in {A/below,B/left,C/below,S/above,E/left,F/above}
{
fill (point) circle (.8pt);
node[position=3pt] at (point) {$point$};
}

end{tikzpicture}
end{document}


and got



enter image description here



How can I draw a circle (sphere) passing through four points B, C, E, F?










share|improve this question























  • A circle is already uniquely fixed by 3 (noncollinear) points. There exist answers that show you how to find such a circle. E.g. tex.stackexchange.com/questions/461161/… (Sorry for advertising;-)

    – marmot
    58 mins ago













  • @marmot Is it true in 3D?

    – minhthien_2016
    44 mins ago











  • I believe that an orthographic projection of a sphere is a circle. The subtle point is whether the projected circle runs through the points you indicate, something that I cannot decide without more information on how the sphere is determined.

    – marmot
    40 mins ago











  • The sphere has centre is midpoint of the segment EC.

    – minhthien_2016
    37 mins ago











  • OK this tells you already where the center of the circle will be. If you know that E and C are on the boundary, this completely fixes the circle. If you load the call library, you could do draw let p1=($(E)-(C)$), n1={veclen(x1,y1)/2} in ($(E)!0.5!(C)$) circle (n1);

    – marmot
    30 mins ago
















1















I am trying to draw a circle (sphere) passing through four points B, C, E, F like this picture enter image description here



I tried with tikz-3dplot and my code



documentclass[border=3mm,12pt]{standalone}
usepackage{fouriernc}
usepackage{tikz,tikz-3dplot}
usepackage{tkz-euclide}
usetkzobj{all}

usetikzlibrary{intersections,calc,backgrounds}

begin{document}

tdplotsetmaincoords{70}{110}
%tdplotsetmaincoords{80}{100}
begin{tikzpicture}[tdplot_main_coords,scale=1.5]
pgfmathsetmacroa{3}
pgfmathsetmacrob{4}
pgfmathsetmacroh{5}

% definitions
path
coordinate(A) at (0,0,0)
coordinate (B) at (a,0,0)
coordinate (C) at (0,b,0)
coordinate (S) at (0,0,h)
coordinate (E) at ({a*h^2/(a*a + h*h)},0,{(a*a*h)/(a*a + h*h)})
coordinate (F) at (0,{(b*h*h)/(b*b + h*h)},{(b*b*h)/(b*b + h*h)});
draw[dashed,thick]
(A) -- (B) (A) -- (C) (A) -- (E) (S)--(A) (F)--(A);
draw[thick]
(S) -- (B) -- (C) -- cycle;
draw[thick]
(F) -- (B) (C)--(E) (F)--(E);
tkzMarkRightAngle(S,E,A);
tkzMarkRightAngle(S,F,A);

foreach point/position in {A/below,B/left,C/below,S/above,E/left,F/above}
{
fill (point) circle (.8pt);
node[position=3pt] at (point) {$point$};
}

end{tikzpicture}
end{document}


and got



enter image description here



How can I draw a circle (sphere) passing through four points B, C, E, F?










share|improve this question























  • A circle is already uniquely fixed by 3 (noncollinear) points. There exist answers that show you how to find such a circle. E.g. tex.stackexchange.com/questions/461161/… (Sorry for advertising;-)

    – marmot
    58 mins ago













  • @marmot Is it true in 3D?

    – minhthien_2016
    44 mins ago











  • I believe that an orthographic projection of a sphere is a circle. The subtle point is whether the projected circle runs through the points you indicate, something that I cannot decide without more information on how the sphere is determined.

    – marmot
    40 mins ago











  • The sphere has centre is midpoint of the segment EC.

    – minhthien_2016
    37 mins ago











  • OK this tells you already where the center of the circle will be. If you know that E and C are on the boundary, this completely fixes the circle. If you load the call library, you could do draw let p1=($(E)-(C)$), n1={veclen(x1,y1)/2} in ($(E)!0.5!(C)$) circle (n1);

    – marmot
    30 mins ago














1












1








1








I am trying to draw a circle (sphere) passing through four points B, C, E, F like this picture enter image description here



I tried with tikz-3dplot and my code



documentclass[border=3mm,12pt]{standalone}
usepackage{fouriernc}
usepackage{tikz,tikz-3dplot}
usepackage{tkz-euclide}
usetkzobj{all}

usetikzlibrary{intersections,calc,backgrounds}

begin{document}

tdplotsetmaincoords{70}{110}
%tdplotsetmaincoords{80}{100}
begin{tikzpicture}[tdplot_main_coords,scale=1.5]
pgfmathsetmacroa{3}
pgfmathsetmacrob{4}
pgfmathsetmacroh{5}

% definitions
path
coordinate(A) at (0,0,0)
coordinate (B) at (a,0,0)
coordinate (C) at (0,b,0)
coordinate (S) at (0,0,h)
coordinate (E) at ({a*h^2/(a*a + h*h)},0,{(a*a*h)/(a*a + h*h)})
coordinate (F) at (0,{(b*h*h)/(b*b + h*h)},{(b*b*h)/(b*b + h*h)});
draw[dashed,thick]
(A) -- (B) (A) -- (C) (A) -- (E) (S)--(A) (F)--(A);
draw[thick]
(S) -- (B) -- (C) -- cycle;
draw[thick]
(F) -- (B) (C)--(E) (F)--(E);
tkzMarkRightAngle(S,E,A);
tkzMarkRightAngle(S,F,A);

foreach point/position in {A/below,B/left,C/below,S/above,E/left,F/above}
{
fill (point) circle (.8pt);
node[position=3pt] at (point) {$point$};
}

end{tikzpicture}
end{document}


and got



enter image description here



How can I draw a circle (sphere) passing through four points B, C, E, F?










share|improve this question














I am trying to draw a circle (sphere) passing through four points B, C, E, F like this picture enter image description here



I tried with tikz-3dplot and my code



documentclass[border=3mm,12pt]{standalone}
usepackage{fouriernc}
usepackage{tikz,tikz-3dplot}
usepackage{tkz-euclide}
usetkzobj{all}

usetikzlibrary{intersections,calc,backgrounds}

begin{document}

tdplotsetmaincoords{70}{110}
%tdplotsetmaincoords{80}{100}
begin{tikzpicture}[tdplot_main_coords,scale=1.5]
pgfmathsetmacroa{3}
pgfmathsetmacrob{4}
pgfmathsetmacroh{5}

% definitions
path
coordinate(A) at (0,0,0)
coordinate (B) at (a,0,0)
coordinate (C) at (0,b,0)
coordinate (S) at (0,0,h)
coordinate (E) at ({a*h^2/(a*a + h*h)},0,{(a*a*h)/(a*a + h*h)})
coordinate (F) at (0,{(b*h*h)/(b*b + h*h)},{(b*b*h)/(b*b + h*h)});
draw[dashed,thick]
(A) -- (B) (A) -- (C) (A) -- (E) (S)--(A) (F)--(A);
draw[thick]
(S) -- (B) -- (C) -- cycle;
draw[thick]
(F) -- (B) (C)--(E) (F)--(E);
tkzMarkRightAngle(S,E,A);
tkzMarkRightAngle(S,F,A);

foreach point/position in {A/below,B/left,C/below,S/above,E/left,F/above}
{
fill (point) circle (.8pt);
node[position=3pt] at (point) {$point$};
}

end{tikzpicture}
end{document}


and got



enter image description here



How can I draw a circle (sphere) passing through four points B, C, E, F?







3d tikz-3dplot






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked 1 hour ago









minhthien_2016minhthien_2016

1,102815




1,102815













  • A circle is already uniquely fixed by 3 (noncollinear) points. There exist answers that show you how to find such a circle. E.g. tex.stackexchange.com/questions/461161/… (Sorry for advertising;-)

    – marmot
    58 mins ago













  • @marmot Is it true in 3D?

    – minhthien_2016
    44 mins ago











  • I believe that an orthographic projection of a sphere is a circle. The subtle point is whether the projected circle runs through the points you indicate, something that I cannot decide without more information on how the sphere is determined.

    – marmot
    40 mins ago











  • The sphere has centre is midpoint of the segment EC.

    – minhthien_2016
    37 mins ago











  • OK this tells you already where the center of the circle will be. If you know that E and C are on the boundary, this completely fixes the circle. If you load the call library, you could do draw let p1=($(E)-(C)$), n1={veclen(x1,y1)/2} in ($(E)!0.5!(C)$) circle (n1);

    – marmot
    30 mins ago



















  • A circle is already uniquely fixed by 3 (noncollinear) points. There exist answers that show you how to find such a circle. E.g. tex.stackexchange.com/questions/461161/… (Sorry for advertising;-)

    – marmot
    58 mins ago













  • @marmot Is it true in 3D?

    – minhthien_2016
    44 mins ago











  • I believe that an orthographic projection of a sphere is a circle. The subtle point is whether the projected circle runs through the points you indicate, something that I cannot decide without more information on how the sphere is determined.

    – marmot
    40 mins ago











  • The sphere has centre is midpoint of the segment EC.

    – minhthien_2016
    37 mins ago











  • OK this tells you already where the center of the circle will be. If you know that E and C are on the boundary, this completely fixes the circle. If you load the call library, you could do draw let p1=($(E)-(C)$), n1={veclen(x1,y1)/2} in ($(E)!0.5!(C)$) circle (n1);

    – marmot
    30 mins ago

















A circle is already uniquely fixed by 3 (noncollinear) points. There exist answers that show you how to find such a circle. E.g. tex.stackexchange.com/questions/461161/… (Sorry for advertising;-)

– marmot
58 mins ago







A circle is already uniquely fixed by 3 (noncollinear) points. There exist answers that show you how to find such a circle. E.g. tex.stackexchange.com/questions/461161/… (Sorry for advertising;-)

– marmot
58 mins ago















@marmot Is it true in 3D?

– minhthien_2016
44 mins ago





@marmot Is it true in 3D?

– minhthien_2016
44 mins ago













I believe that an orthographic projection of a sphere is a circle. The subtle point is whether the projected circle runs through the points you indicate, something that I cannot decide without more information on how the sphere is determined.

– marmot
40 mins ago





I believe that an orthographic projection of a sphere is a circle. The subtle point is whether the projected circle runs through the points you indicate, something that I cannot decide without more information on how the sphere is determined.

– marmot
40 mins ago













The sphere has centre is midpoint of the segment EC.

– minhthien_2016
37 mins ago





The sphere has centre is midpoint of the segment EC.

– minhthien_2016
37 mins ago













OK this tells you already where the center of the circle will be. If you know that E and C are on the boundary, this completely fixes the circle. If you load the call library, you could do draw let p1=($(E)-(C)$), n1={veclen(x1,y1)/2} in ($(E)!0.5!(C)$) circle (n1);

– marmot
30 mins ago





OK this tells you already where the center of the circle will be. If you know that E and C are on the boundary, this completely fixes the circle. If you load the call library, you could do draw let p1=($(E)-(C)$), n1={veclen(x1,y1)/2} in ($(E)!0.5!(C)$) circle (n1);

– marmot
30 mins ago










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