- A staring point.
- We draw the intersection line of two cylinders.
ContourPlot3D[{x^2 + z^2 == 3^2, y^2 + z^2 == 3^2}, {x, -3, 3}, {y, -3, 3}, {z, -3, 3}]
plot = Plot3D[z = Sqrt[3^2 - y^2], {x, -3, 3}, {y, -3, 3}, Mesh -> {{0}}, MeshFunctions -> Function[{x, y, z}, z - Sqrt[3^2 - x^2]], MeshStyle -> Directive@{Thick, Red}, PlotPoints -> 150, MaxRecursion -> 4, PlotStyle -> None, BoundaryStyle -> None, Boxed -> False, Axes -> False, BoxRatios -> Automatic]; square = Graphics3D[{{FaceForm[], EdgeForm[Cyan], Polygon[{{-3, -3, 0}, {3, -3, 0}, {3, 3, 0}, {-3, 3, 0}}]}}]; Show[plot, square]
