To use the three point perspective coordinate systems, one has to use the syntax
(tpp cs:x=1,y=2,z=3)
to specify the point (1,2,3). I find this a bit cumbersome to write. Is there a way to automatically treat coordinates of the form (1,2,3) as coordinates in the three point perspective coordinate system?
I know that I could try to define a new command which translates \tpp{1,2,3} into (tpp cs:x=1,y=2,z=3).
We can introduce a key 3d coordinate is with the choice
default (→ \pgfpointxyz) andperspective (→ \pgfpointperspectivexyz).You just have to use the right choice at the right time.
The red node should not use the perspective coordinate system but you can use 3d coordinate is = default for it or the explicit (xyz cs: x=4, y=0, z=0).
\documentclass[tikz]{standalone}
\usetikzlibrary{perspective}
\makeatletter
\tikzset{
3d coordinate is/.is choice,
3d coordinate is/default/.code={\def\tikz@parse@splitxyz##1##2##3,##4,{%
\def\pgfutil@next{##1{\pgfpointxyz{##2}{##3}{##4}}}}},
3d coordinate is/perspective/.code={\def\tikz@parse@splitxyz##1##2##3,##4,{%
\def\pgfutil@next{##1{\pgfpointperspectivexyz{##2}{##3}{##4}}}}}}
\makeatother
\begin{document}
\begin{tikzpicture}[isometric view, perspective={p = {(4,0,0)}, q = {(0,4,0)}}]
\node[fill=red,circle,inner sep=1.5pt,label=above:p] at (4,0,0){};
\foreach \i in {0,...,100}
\filldraw[fill = gray] (tpp cs: x=\i, y=0, z=0)
-- (tpp cs: x=\i+0.5, y=0, z=0) -- (tpp cs: x=\i+0.5, y=2, z=0)
-- (tpp cs: x=\i, y=2, z=0) -- cycle;
\end{tikzpicture}
\begin{tikzpicture}[
isometric view,
perspective={p = {(4,0,0)}, q = {(0,4,0)}},
3d coordinate is = perspective]
\node[fill=red,circle,inner sep=1.5pt,label=above:p] at (xyz cs: x=4, y=0, z=0){};
\foreach \i in {0,...,100}
\filldraw[fill = gray] (\i, 0, 0)
-- (\i+0.5, 0, 0) -- (\i+0.5, 2, 0)
-- (\i, 2, 0) -- cycle;
\end{tikzpicture}
\end{document}
