# TikZ: Z-index with Bloch Sphere

This is a follow-up question regarding this. I have improved the answer posted but still not fully satisfied. My output now looks like the following:

The desired (photoshopped) output is:

Thanks in advance!

\documentclass[border= 5pt]{standalone}
\usepackage{blochsphere} % also loads tikz package
\usepackage{tikz-3dplot}
\begin{document}
\begin{blochsphere}[ radius = 1.5 cm, tilt = 15, rotation = -45, opacity = 0.20]
% Drawing the equatorial plane
\tdplotsetmaincoords{105}{45}
\tdplotsetrotatedcoords{0}{0}{0}
% Red half (the problem is here)
\begin{scope}[tdplot_main_coords,canvas is xy plane at z=0,on layer=back]
\fill[red!40,opacity=0.5](-2.5,-2.5)--(-135:1.5)arc(-135:45:1.5)--(2.5,2.5)--(6,-6);
\end{scope}
% Draw the sphere and grid
\drawBallGrid[style={opacity=0.5, color = blue, loosely dashed}]{180}{180}
% Axes (X, Y, Z)
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.50]{x}{90}{90}
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.50]{y}{90}{00}
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.15]{z}{00}{00}
% Blue half
\begin{scope}[tdplot_main_coords,canvas is xy plane at z=0,on layer=front]
\fill[blue!40,opacity=0.5](-2.5,-2.5)--(225:1.5)arc(225:45:1.5)--(2.5,2.5)--(-6,6);
\end{scope}
\end{blochsphere}
\end{document}


## 1 Answer

You can use reverseclip from here and I would not distort the square but rather just change the coordinates.

\documentclass[border= 5pt]{standalone}
\usepackage{blochsphere} % also loads tikz package
\usepackage{tikz-3dplot}
\tikzset{reverseclip/.style={insert path={(current bounding box.south west) rectangle
(current bounding box.north east)} }}
\begin{document}
\begin{blochsphere}[ radius = 1.5 cm, tilt = 15, rotation = -45, opacity = 0.20]
% Drawing the equatorial plane
\tdplotsetmaincoords{105}{45}
\tdplotsetrotatedcoords{0}{0}{0}
\begin{scope}[tdplot_main_coords,canvas is xy plane at z=0]
\path (-3.5,-3.5) rectangle (3.5,3.5);
\end{scope}
\begin{scope}[tdplot_screen_coords]
\clip (0,0) circle[radius=1.5cm] [reverseclip];
\begin{scope}[tdplot_main_coords,canvas is xy plane at z=0]
\fill[red!40,opacity=0.5](-3.5,-3.5)--(3.5,3.5) -- (3.5,-3.5);
\end{scope}
\end{scope}
% Draw the sphere and grid
\drawBallGrid[style={opacity=0.5, color = blue, loosely dashed}]{180}{180}
% Axes (X, Y, Z)
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.50]{x}{90}{90}
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.50]{y}{90}{00}
\drawStatePolar[axisarrow = true, statewidth = 0.5, scale = 1.15]{z}{00}{00}
% Blue half
\begin{scope}[tdplot_main_coords,canvas is xy plane at z=0,on layer=front]
\fill[blue!40,opacity=0.5](-3.5,-3.5)--(225:1.5)arc(225:45:1.5)--(3.5,3.5)
-- (-3.5,3.5);
\end{scope}
\end{blochsphere}
\end{document}


• Thank you again for the answer! – M. Al Jumaily Aug 7 '19 at 18:47