hello-tikz.tex

\documentclass[dvipdfmx,uplatex]{jsarticle}
\usepackage{tikz}
\usetikzlibrary{intersections, calc, arrows.meta, angles, quotes}
\usepackage{tkz-euclide}

\newcommand{\axis}[1]{\mathrm{#1}}

\begin{document}

\begin{tikzpicture}

  % 視錐台を描く
  \coordinate (O) at (0, 7.5);
  \coordinate (CameraAxisZ) at (12, 7.5);
  \coordinate (FrustumFarT) at (10, 12.5);
  \coordinate (FrustumFarB) at (10, 2.5);
  \draw[->] (O)--(CameraAxisZ);
  \draw [name path=FrustumT] (O)--(FrustumFarT);
  \draw [name path=FrustumB] (O)--(FrustumFarB);
  \draw (O) node[left] {O};
  \draw (CameraAxisZ) node[right] {$ \axis{z} $};

  % サーフィスを描く
  \coordinate (SurfaceL) at (6, 7.5);
  \coordinate (SurfaceR) at (8.5, 9.5);
  \draw (SurfaceL) node[below] {$ z $};
  \draw [very thick] (SurfaceL)--(SurfaceR) node[midway,auto=right,sloped]{$ \Delta A $};
  \coordinate (SurfaceZProjR) at ($ (O)!(SurfaceR)!(CameraAxisZ) $);
  \draw (SurfaceZProjR) node[below] {$ z + \Delta z $};
  \draw [dashed] (SurfaceZProjR)--(SurfaceR);

  % シャドウマップの軸を描く
  \coordinate (ShadowMapAxisL) at (0, 11);
  \coordinate (ShadowMapAxisR) at (9, 14);
  \draw[->] (ShadowMapAxisL)--(ShadowMapAxisR);
  \draw (ShadowMapAxisR) node[right] {$ \axis{u} $};

  % シャドウマップ上のピクセルを描く
  \coordinate (ShadowMapPixelL) at ($ (ShadowMapAxisL)!(SurfaceL)!(ShadowMapAxisR) $);
  \coordinate (ShadowMapPixelR) at ($ (ShadowMapAxisL)!(SurfaceR)!(ShadowMapAxisR) $);
  \draw [dashed] (SurfaceL)--(ShadowMapPixelL);
  \draw [dashed] (SurfaceR)--(ShadowMapPixelR);
  \draw [very thick] (ShadowMapPixelL) node[above]{$ S(z) $} -- node[midway,above,sloped]{$ \Delta S $} node[at end,above]{$ S(z + \Delta z) $} (ShadowMapPixelR);

  % NearPlane を描く
  \coordinate (NearPlaneP) at (3, 7.5);
  \draw (NearPlaneP) node[below] {$ z_n $};
  \path [name path=NearPlane0] (3, 10)--(3, 0);
  \path [name intersections={of=NearPlane0 and FrustumT}];
  \coordinate (NearPlaneT) at (intersection-1);
  \path [name intersections={of=NearPlane0 and FrustumB}];
  \coordinate (NearPlaneB) at (intersection-1);
  \draw [name path=NearPlane, dashed] (NearPlaneT)--(NearPlaneB);

  % カメラ上のピクセルを描く
  \draw [dashed, name path=RayT] (O)--(SurfaceR);
  \path [name intersections={of=RayT and NearPlane}];
  \coordinate (PixelT) at (intersection-1);
  \draw [very thick] (NearPlaneP)--(PixelT) node[midway,auto=left]{$ \Delta P $};

\end{tikzpicture}

\begin{tikzpicture}[scale=2]

  % 視錐台を描く
  \coordinate (O) at (4, 7.5);
  \coordinate (CameraAxisZ) at (10, 7.5);
  \draw[->] (O)--(CameraAxisZ);
  \draw (O) node[left] {O};
  \draw (CameraAxisZ) node[right] {$ \axis{z} $};

  % サーフィスを描く
  \coordinate (SurfaceL) at (6, 7.5);
  \coordinate (SurfaceR) at (8.5, 9.5);
  \draw [very thick] (SurfaceL)--(SurfaceR) node[midway,auto=left,sloped]{$ \Delta A $};
  \coordinate (SurfaceZProjR) at ($ (O)!(SurfaceR)!(CameraAxisZ) $);
  \draw [dashed] (SurfaceZProjR)--(SurfaceR);
  \draw [gray] (SurfaceZProjR) .. controls +(30:4mm) and +(-30:4mm) .. (SurfaceR) node[black,midway,fill=white]{$ \Delta y $};
  \draw [gray] (SurfaceL) .. controls +(-45:4mm) and +(-135:4mm) .. (SurfaceZProjR) node[black,midway,fill=white]{$ \Delta z $};

  % 補助線
  \coordinate (H) at ($ (SurfaceL)!0.75!90:(SurfaceR) $);
  \draw [dashed] (SurfaceL)--(H);
  \tkzMarkRightAngle[size=0.15](SurfaceR,SurfaceL,H);

  \draw pic ["$\theta$",draw,angle radius=5mm,angle eccentricity=1.75]{angle = H--SurfaceL--O};
  \draw pic ["$90^\circ-\theta$",draw,angle radius=5mm,angle eccentricity=2.5]{angle = CameraAxisZ--SurfaceL--SurfaceR};
  \draw pic ["$\theta$",draw,angle radius=5mm,angle eccentricity=1.75]{angle = SurfaceL--SurfaceR--SurfaceZProjR};

\end{tikzpicture}
\end{document}