graphics3d - How to make a blob in 3D?

I am trying to make a blob like the one shown below, but in 3D so I can rotate it. I'm trying to use ParametricPlot3D or SphericalPlot3D. I can make a sphere easily. But my knowledge of how to modify the sphere to make it bulge out in a few places in limited. Anyone have any suggestions? I'd like to make it non symmetric so it look like a random blob like the one below. If I can create the outside blob I'm sure I can create an inside one. I can than place the vectors in the appropriate places. I am a teacher trying to illustrate how to use the divergence theorem on a region like this. Any suggestions would be appreciated. Thank you.

Answer

This can also be made a little lumpier with spherical harmonics.

realization[r_] := 

  Assuming[{0 <= θ <= π, 0 <= φ <= 2 π},
    Simplify[r + Abs[ComplexExpand[Plus @@ Flatten[
      Table[ RandomReal[{-1, 1}] 1/(l^2 + m^2)
        SphericalHarmonicY[l, m, θ, φ], 
        {l, 1, 4}, {m, 0, l}]
  ]]]]]

Block[{inner, outer},
  outer = realization[1];
  inner = realization[1/2];

  Show[
    SphericalPlot3D[outer, {θ, 0, π}, {φ, 0, 2 π}, 
      PlotStyle -> Directive[Orange, Opacity[0.2], Specularity[White, 10]], 
      Mesh -> None, PlotPoints -> 50],
    SphericalPlot3D[inner, {θ, 0, π}, {φ, 0, 2 π}, 
      PlotStyle -> Directive[GrayLevel[0.4], Opacity[0.2], Specularity[White, 10]], 
      Mesh -> None, PlotPoints -> 50],
    Axes -> False, Boxed -> False
]]

Comments

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plotting - Mathematica: 3D plot based on combined 2D graphs

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