I’m using Tikz to create an isometric view of a cylinder. The flat bases of the cylinder may be angled 45° around the y axis. I now need to connect these bases with straight lines to render a cylinder. For example:

begin{tikzpicture}
    begin{scope}[x={(0.866cm,-0.5cm)}, z = {(-0.866cm, -0.5cm)}] %isometric
        %coordinate system
        draw[color = red] (0, 0, 0) -- ++(0, 0, 1);
        draw[color = blue] (0, 0, 0) -- ++(0, 1, 0);
        draw (0, 0, 0) -- ++(1, 0, 0);

        %Useful Parameters
        pgfmathsetmacro{radff}{0.2/sqrt(2)}

        
        draw (-2,0,-2) circle[x = {(1, 0, 0)}, y = {(0, 1, 0)}, radius=0.2];
        draw[dashed] (-2,0,0) circle[x = {(1, 0, 0)}, y = {(0, 1, 0)}, radius=0.2];

        draw (-2+radff, -radff, -2) -- ++(0, 0, 3.8);
        draw (-2-radff, +radff, -2) -- ++(0, 0, 4.2);

        draw (-2,0,+2) circle[x = {(1, 0, -1)}, y = {(0, 1, 0)}, radius=0.2];
    end{scope}

end{tikzpicture}

Now when I switch to a flat view this obviously does not work.

begin{scope}[x={(0cm,0cm)}, z = {(1cm, 0cm)}] %left
...
end{scope}

The circles here are rendered correctly, however the connections do not work.

Is there a good way to calculate the angle or the offset of the starting point of those connecting lines in 3d space? Additionally I need to calculate the change in length of those connections.

Unfortunately I have rather poor spacial comprehension and have trouble visualizing the lengths and angles I need to calculate. Answers contain ing an implementation using pgfmath would be greatly appreciated.