# Plotting region with negative Gaussian curvature?

I am plotting a surface using ParametricPlot3D. Is there a way that only the region with negative Gaussian curvature is plotted?

• Try RegionFunction! It would be very helpful if you provide a minimal example. Aug 10, 2020 at 7:50
• @UlrichNeumann Thank you for your reply. supposing that I am plotting a cyclide ParametricPlot3D[ ResourceFunction["Cyclide"][.3, 1.5, {u, v}], {u, -\[Pi], \[Pi]}, {v, -2 \[Pi], 2 \[Pi]}] and I only wanted to plot the regions with negative Gaussian curvature. I wasn't sure how to use RegionFunction. thank you for your reply! Aug 10, 2020 at 8:01
• If you know the curvature curv[u,v] try ParametricPlot3D[…,RegionFunction->Function[{u,v},curv[u,v]<0]] Aug 10, 2020 at 8:13

There is a ResourceFunction that can compute Gaussian curvature which allows you to incorporate the comment by Ulrich Neumann
Clear[surf, curv]