graphics3d - Convex hull of a 3D object?

I am trying to find a convex hull command for a Graphics3D object. Does it exist in Mathematica?

egg = Graphics3D[Cuboid /@ Position[DiskMatrix[{12, 10, 8}], 1]]

Mathematica graphics

The ConvexHull command of the "ComputationalGeometry`" package does not work on 3D objects:

Needs["ComputationalGeometry`"]
ConvexHull[egg]

Mathematica graphics

Answer

Since ConvexHull doesn't support 3D points (and you incorrectly tried to compute the ConvexHull of the Graphics object) your code didn't work.

Here is one way to do what I think you want (I left out of the step of the Cuboids but if you want that basically just offset your convex hull).

Needs["TetGenLink`"]

pos = Position[DiskMatrix[{12, 10, 8}], 1];

Graphics3D[Point@pos]

Mathematica graphics

{pts, surface} = TetGenConvexHull[pos];
Graphics3D[GraphicsComplex[pts, Polygon[surface]]]

Mathematica graphics

If you do want to compute the ConvexHull of your Graphics3D object you can extract the points from the InputForm. This is fragile and will only work for this simple case.

pos = InputForm[egg][[1, 1, All, 1]]

Comments

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I have a list of 4D data (x position, y position, amplitude, wavelength). I want to plot x, y, and amplitude on a 3D plot and have the color of the points correspond to the wavelength. I have seen many examples using functions to define color but my wavelength cannot be expressed by an analytic function. Is there a simple way to do this? Answer Here a another possible way to visualize 4D data: data = Flatten[Table[{x, y, x^2 + y^2, Sin[x - y]}, {x, -Pi, Pi,Pi/10}, {y,-Pi,Pi, Pi/10}], 1]; You can use the function Point along with VertexColors . Now the points are places using the first three elements and the color is determined by the fourth. In this case I used Hue, but you can use whatever you prefer. Graphics3D[ Point[data[[All, 1 ;; 3]], VertexColors -> Hue /@ data[[All, 4]]], Axes -> True, BoxRatios -> {1, 1, 1/GoldenRatio}]

plotting - Adding a thick curve to a regionplot

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