Argthtjtr

I have the following MWE:

%&lualatex

% !TeX program = lualatex

documentclass{standalone}

usepackage{pgfplots}

pgfplotsset{compat=newest}

begin{document}

begin{tikzpicture}

begin{axis}[

width=8.5cm,

height=2in,

]

addplot3[surf,mesh/rows=2,fill=gray,opacity=0.2] coordinates {

    (0.3,0,-1) (.3,7,-1) 



    (0.3,0,1) (.3,7,1)

};

end{axis}

end{tikzpicture}

end{document}

which gives:

Are there possibilities to render this (filled) region elliptical instead of the (filled) rectangular region (using the same coordinates).

Update 1 To avoid confusion, let us assume that the coordinate set

X belongs to {(x_i,y_i,z_i)|i={1,2,3,4}}

here the i's indicate the corners and the X can randomly vary depending upon the desired dataset.

Something like this?

documentclass{standalone}

usepackage{pgfplots}

usetikzlibrary{3d}

pgfplotsset{compat=newest}

begin{document}

begin{tikzpicture}

  begin{axis}[

  width=8.5cm,

  height=2in,

  ]

  begin{scope}[canvas is yz plane at x=0.3]

    filldraw[fill = gray!10,rounded corners = 1mm, draw = black] (0,-1) rectangle (7,1);

    fill[red, opacity = 0.4] (3.5, 0) ellipse (3cm and 1cm);

    end{scope}



  addplot3[surf,mesh/rows=2,fill=gray,opacity=0.2] coordinates {

      (0.3,0,-1) (.3,7,-1)



      (0.3,0,1) (.3,7,1)

  };

  end{axis}

end{tikzpicture}

end{document}

You can comment out the line filldraw[fill = gray!10,rounded corners = 1mm, draw = black] (0,-1) rectangle (7,1); if you want to remove the plane

First of all, let me start by saying that I don't think there is anything wrong with caverac's answer; rather I like and upvoted it. (One could add a local transformation to rotate the plane the ellipse is in.) Nevertheless, the arguably simplest way to generate an ellipse in pgfplots is to plot it. This code and animation show how one can do that.

documentclass[tikz,border=3.14mm]{standalone}

usepackage{pgfplots}

pgfplotsset{compat=newest}

begin{document}

foreach X in {5,15,...,355}

{begin{tikzpicture}[declare function={rot=X;a=3;b=1;}]

path[use as bounding box] (-1,-1) rectangle (9,5);

begin{axis}[xmin=-3,xmax=3,ymin=-3,ymax=3,zmin=-1,zmax=1,

width=8.5cm,

height=2in,

]

addplot3[fill=gray,opacity=0.2,domain=0:360,smooth]  

({a*cos(x)*cos(rot)},{a*cos(x)*sin(rot)},{b*sin(x)});

end{axis}

end{tikzpicture}}

end{document}