Bucle cuadrado hecho de alambre cilíndrico con sección transversal uniforme

Question

Estoy tratando de dibujar un bucle cuadrado hecho de alambre cilíndrico grueso con una sección transversal uniforme que se encuentra en el suelo como se muestra en Square_Loop.png. Trazar un bucle en 3D como un marco rectangular dibujado con líneas que no tienen grosor parece bastante sencillo en PSTricks y/o Ti.kZ. Sin embargo, aumentar cierta dimensionalidad de la sección transversal no resulta nada fácil. Gracias por la ayuda por adelantado.

Answer 1

\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{tikz-3dplot}
\usetikzlibrary{3d,angles,quotes}
\begin{document}
\tdplotsetmaincoords{70}{20}
\begin{tikzpicture}[tdplot_main_coords,thick]
 \draw[-stealth] (0,0,0) -- (6,0,0) node[below]{$x$};
 \draw[-stealth] (0,0,0) -- (0,-6,0) node[below right]{$y$};
 \draw[-stealth] (0,0,0) -- (0,0,4) node[left]{$z$};
 \begin{scope}[canvas is xy plane at z=0]
  \draw[rounded corners] (0,0) rectangle (2,-4);
  \draw[rounded corners] (0.2,-0.2) rectangle (1.8,-3.8);
  \node[fill,circle,inner sep=2pt,transform shape] (blob) at (1,-2){};
 \end{scope}
 \draw[dashed] (blob.center) -- (5,-2,0) coordinate(B) -- (5,-2,4) node[circle,draw,inner
 sep=1.5pt,solid,label=right:$A$](A){};
 \draw[-stealth] (blob.center) -- (A);
 \begin{scope}[canvas is xz plane at y=-2,transform shape]
  \pic[draw,angle radius=2cm,"$\alpha$",angle eccentricity=1.3] {angle=B--blob--A};
 \end{scope}
 \draw[semithick] (0,-4,0) -- (0,-4,1.5) (2,0,0) -- (2,0,1.5);
 \begin{scope}[canvas is yz plane at x=0,transform shape]
  \path (-4,1.2) -- (0,1.2) node[midway,above,transform shape=false]{$b$};
  \pgflowlevelsynccm
  \draw[stealth-stealth] (-4,1.2) -- (0,1.2);
 \end{scope} 
 \begin{scope}[canvas is xz plane at y=0,transform shape]
  \path (2,1.2) -- (0,1.2) node[midway,above,transform shape=false]{$a$};
  \pgflowlevelsynccm
  \draw[stealth-stealth] (2,1.2) -- (0,1.2);
 \end{scope} 
\end{tikzpicture}
\end{document}

En cuanto al efecto 3D, fallé. Esto es lo mejor que se me ocurrió en un tiempo razonable.

\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{tikz-3dplot}
\usetikzlibrary{3d,angles,quotes,calc}
\begin{document}
\tdplotsetmaincoords{70}{20}
\begin{tikzpicture}[tdplot_main_coords,thick]
 \draw[-stealth] (0,0,0) -- (6,0,0) node[below]{$x$};
 \draw[-stealth] (0,0,0) -- (0,-6,0) node[below right]{$y$};
 \draw[-stealth] (0,0,0) -- (0,0,4) node[left]{$z$};
 \begin{scope}[canvas is xy plane at z=0,transform shape]
  \draw[rounded corners] (0,0) rectangle (2,-4);
  \draw[rounded corners] (0.2,-0.2) rectangle (1.8,-3.8);
  \node[fill,circle,inner sep=2pt,transform shape] (blob) at (1,-2){};
  \begin{scope}
   \clip[rounded corners] (0,0) rectangle (2,-4) 
   (1.8,-3.8) -| (0.2,-0.2) -- (1.8,-0.2) -- cycle;
   \shade[top color=black!80,bottom color=black!70,middle color=gray!50,
   shading angle=-35] (0.3,0.2) rectangle (1.7,-0.3);
   \shade[top color=black!80,bottom color=black!70,middle color=gray!50,
   shading angle=-35] (0.3,-4.1) rectangle (1.7,-3.6);
   \shade[top color=black!80,bottom color=black!70,middle color=gray!50,
   shading angle=52] (-0.2,-0.3) rectangle (0.3,-3.7);
   \shade[top color=black!80,bottom color=black!70,middle color=gray!50,
   shading angle=52] (1.6,-0.3) rectangle (2.1,-3.7);
   \begin{scope}
    \clip (0,0) rectangle (0.3,-0.3);
    \shade[ball color=gray!70] (0.3,-0.3) circle[radius=0.3];
   \end{scope}
   \begin{scope}
    \clip (2,0) rectangle (1.7,-0.3);
    \shade[ball color=white] (1.7,-0.3) circle[radius=0.3];
   \end{scope}
   \begin{scope}
    \clip (0,-4) rectangle (0.3,-3.7);
    \shade[ball color=gray!30] (0.3,-3.7) circle[radius=0.3];
   \end{scope}
   \begin{scope}
    \clip (1.7,-4) rectangle (2,-3.7);
    \shade[ball color=white] (1.7,-3.7) circle[radius=0.3];
   \end{scope}
  \end{scope}
 \end{scope}
 \begin{scope}[tdplot_screen_coords]
 \end{scope}
 \draw[dashed] (blob.center) -- (5,-2,0) coordinate(B) -- (5,-2,4) node[circle,draw,inner
 sep=1.5pt,solid,label=right:$A$](A){};
 \draw[-stealth] (blob.center) -- (A);
 \begin{scope}[canvas is xz plane at y=-2,transform shape]
  \pic[draw,angle radius=2cm,"$\alpha$",angle eccentricity=1.3] {angle=B--blob--A};
 \end{scope}
 \draw[semithick] (0,-4,0) -- (0,-4,1.5) (2,0,0) -- (2,0,1.5);
 \begin{scope}[canvas is yz plane at x=0,transform shape]
  \path (-4,1.2) -- (0,1.2) node[midway,above,transform shape=false]{$b$};
  \pgflowlevelsynccm
  \draw[stealth-stealth] (-4,1.2) -- (0,1.2);
 \end{scope} 
 \begin{scope}[canvas is xz plane at y=0,transform shape]
  \path (2,1.2) -- (0,1.2) node[midway,above,transform shape=false]{$a$};
  \pgflowlevelsynccm
  \draw[stealth-stealth] (2,1.2) -- (0,1.2);
 \end{scope} 
\end{tikzpicture}
\end{document}