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plotting - Traces of the level surface $z=4x^2+y^2$


I came up with this method to plot the traces of the surface $z=4x^2+y^2$, in this case for $z=1$, 2, 3, and 4.


ContourPlot3D[{z == 4 x^2 + y^2, z == 1, z == 2, z == 3, 
  z == 4}, {x, -2, 2}, {y, -2, 2}, {z, 0, 4.01},
 ContourStyle -> {Opacity[0.3]},
 PlotPoints -> 30, MaxRecursion -> 3,
 Mesh -> {{1, 2, 3, 4}}, MeshFunctions -> {#3 &},
 MeshStyle -> {Thick, Red},

 AxesLabel -> {"x", "y", "z"}]

Which produces this image:


enter image description here


I am now looking for a way to hide the surface $z=4x^2+y^2$, but keep the planes and the mesh curves.


Any suggestions?


Update:


Consider obtaining traces for the surface $z=y^2-x^2$ using technique shown by MichaelE2.


ContourPlot3D[z, {x, -2, 2}, {y, -2, 2}, {z, -1.5, 1.5}, 
 Contours -> {-1, 0, 1}, ContourStyle -> {Opacity[0.3]}, 

 PlotPoints -> 30, MaxRecursion -> 3, Mesh -> {{0}}, 
 MeshFunctions -> {Function[{x, y, z}, z - (y^2 - x^2)]}, 
 MeshStyle -> Directive[Thick, Red], AxesLabel -> Automatic]

Image:


enter image description here


ContourPlot3D[x, {x, -2, 2}, {y, -2, 2}, {z, -1.5, 1.5}, 
 Contours -> {-1, 0, 1}, ContourStyle -> {Opacity[0.3]}, 
 PlotPoints -> 30, MaxRecursion -> 3, Mesh -> {{0}}, 
 MeshFunctions -> {Function[{x, y, z}, z - (y^2 - x^2)]}, 

 MeshStyle -> Directive[Thick, Red], AxesLabel -> Automatic]

Image:


enter image description here


ContourPlot3D[y, {x, -2, 2}, {y, -2, 2}, {z, -1.5, 1.5}, 
 Contours -> {-1, 0, 1}, ContourStyle -> {Opacity[0.3]}, 
 PlotPoints -> 30, MaxRecursion -> 3, Mesh -> {{0}}, 
 MeshFunctions -> {Function[{x, y, z}, z - (y^2 - x^2)]}, 
 MeshStyle -> Directive[Thick, Red], AxesLabel -> Automatic]


Image:


enter image description here


I think this gives students a very simple way to get the traces for a quadratic surface.



Answer



You could omit the (paraboloid) surface and use its formula as a mesh function:


ContourPlot3D[z, {x, -2, 2}, {y, -2, 2}, {z, 0, 4.01}, 
 Contours -> Range[4], ContourStyle -> {Opacity[0.3]}, 
 PlotPoints -> 30, MaxRecursion -> 3, Mesh -> {{0}}, 
 MeshFunctions -> {Function[{x, y, z}, z - (4 x^2 + y^2)]}, 
 MeshStyle -> Directive[Thick, Red], AxesLabel -> Automatic]


Mathematica graphics



You may like the simpler approach above, but if you want to get fancy, you could highlight the ellipses.


ContourPlot3D[z, {x, -2, 2}, {y, -2, 2}, {z, 0, 4.01}, 
 Contours -> Range[4], ContourStyle -> {Opacity[0.3]}, 
 PlotPoints -> 30, MaxRecursion -> 3, Mesh -> {Range[0.5, 3.5], {0}}, 
 MeshShading -> {
  {Opacity[ 0.2], ##} & @@@
   ("DefaultPlotStyle" /. (Method /. Charting`ResolvePlotTheme["Default", ContourPlot3D])),

  {Opacity[0.7], ##} & @@@
   ("DefaultPlotStyle" /. (Method /. Charting`ResolvePlotTheme["Default", ContourPlot3D]))
  }, 
 MeshFunctions -> {#3 &, Function[{x, y, z}, z - (4 x^2 + y^2)]}, 
 MeshStyle -> Directive[Thick, Red], AxesLabel -> {"x", "y", "z"}]

Mathematica graphics


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