# Problem creating 3d intersection of surfaces

I'm trying make an intersection of two surfaces but appears a warning message:

Package pgfplots Warning: You have an axis with empty range (in direction y). R eplacing it with a default range and clearing all plots. on input line 52.

Why this ocurrs?

\documentclass{standalone}

\usepackage{tikz,pgfplots}
\usepgfplotslibrary{colormaps}
\pgfplotsset{compat=1.11}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
domain = -4:4,
zmax   = 50,
colormap/bone,
grid
]
\end{axis}
\end{tikzpicture}

\begin{tikzpicture}
\begin{axis}[axis on top,axis lines=center,xtick=\empty,ytick=\empty,ztick=\empty,view={130}{30},xmax=1.2,ymax=1.2,zmin=0,zmax=0.03]

Compare images because the equation -x^2-y^2.
You got the message "Package pgfplots Warning: You have an axis with empty range (in direction y)" because you set xmax and ymax values but not xmin and ymin. Once you add xmin=0, ymin=0, for example, that message goes away.