\begin{pspicture}(-1,-2)(6,6)

\psset{xMin=0, xMax=5, yMin=0, yMax=5, zMin=0, zMax=5, spotY=30, Alpha=150, yThreeDunit=1, IIIDticks, Dx=1, Dy=1, Dz=1}
\def\xSchnittp{3,0,0}
\def\ySchnittp{0,3,0}
\def\zSchnittp{0,0,4}
\def\xyzSchnittp{3,3,4}
\pstThreeDCoor
\pstThreeDDot[drawCoor=true, linecolor=blue, linewidth=0.1pt](3,3,4)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=blue](\zSchnittp)(3,0,4)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=blue](3,0,4)(\xyzSchnittp)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=blue](\xSchnittp)(3,0,4)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=blue](\zSchnittp)(0,3,4)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=blue](\ySchnittp)(0,3,4)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=blue](0,3,4)(\xyzSchnittp)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=red](3,0,0)(3, -0.4,0)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=red](0,3,0)(-0.4,3,0)
\pstThreeDLine[linewidth=0.1pt, linestyle=dashed, linecolor=red](0,0,4)(0,-0.4,4)
\pstPlanePut[plane =xz](0 ,0.5 , 4.5) {\red 3. Koordinate }
%\setkeys{psset}{arrows=->,arrowsize=0.2}
%\pstThreeDSquare(0,0,0)(3,0,0)(0,4,0)
%\uput[0](0.9,2.25){$\vec{u}$}
\pstPlanePut[plane =xz](3.3,3,4.3){Punkt}
\pstPlanePut[plane =xz](3.3,3,3.9){$\left(a_1, a_2, a_3\right)$}
%\pstThreeDPut(2,0,5.85){\color{red}(3. Koordinate)}
%\uput[-90](2,0,5.85){\color{red}(3. Koordinate)}
%\pstThreeDLine[linecolor=green](0,0,0)(3,3,4)
\pstPlanePut[plane =xz](3,-0.8,0){\color{red}$a_1$}
\pstPlanePut[plane =yz](-0.6,3,0){\color{red}$a_2$}
\pstPlanePut[plane =yz](0,-1,4){\color{red}$a_3$}
%\pstThreeDPut(-0.4,3,0){3}
%\pstThreeDPut(-0.4,0,4){4}
%\pstThreeDPut(
\end{pspicture}