Wolfram Technology Guide: Integrated Geometric Computing  previous | next 
3D Implicit Regions
Mathematica can find regions defined by inequalities not only in 2D but also in 3D.
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Click for copyable input
RegionPlot3D[x^2 + y^3 - z^2 > 0, {x, -2, 2}, {y, -2, 2}, {z, -2, 2}]
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