Is there a problem with ContourPlot[] function?

[juergenkanz (Jürgen Kanz)]

Attached is an image of a CountourPlot. As you can observe, there is a problem with the contour lines at the center of the plot. I hope it can be repaired soon.

[hdolhaine (Hans Dolhaine)]

ContourPlot[x^2 - z^2, {x, -10, 10}, {z, -10, 10}, ImageSize → Large, PlotPoints → 60]

[gianlucagorni]

Just set PlotPoints to an odd number, so that the middle point is sure to be included:

ContourPlot[x^2 - z^2, {x, -10, 10}, {z, -10, 10}, ImageSize -> Large,
  PlotPoints -> 3]

[juergenkanz (Jürgen Kanz)]

Thank you, works perfectly.

[juergenkanz (Jürgen Kanz)]

Thank you.

[hansmilton]

Try PlotPoints->7. The problem still occurs

ContourPlot[x^2 - z^2, {x, -10, 10}, {z, -10, 10}, PlotPoints -> 7]

[gianlucagorni]

It is more complicated than I thought…

[juergenkanz (Jürgen Kanz)]

I agree, the problem is more complicated. At least I could finalize my work with 3 PlotPoints.

ContourPlot[x^2 - z^2, {x, -10, 10}, {z, -10, 10}, PlotPoints -> 3]

[henrikschachner]

It is possible to see what is going on using the option Mesh -> All, depending on PlotPoints (and MaxRecursion):

ContourPlot[x^2 - z^2, {x, -10, 10}, {z, -10, 10}, PlotPoints -> 3, Mesh -> All]