Discretize Graphics3D with Scale and Rotate?

Question

How can I discretize a Graphics3D object that makes use of Scale and Rotate? When I try DiscretizeGraphics I get an EmptyRegion; the documentation warns of this, at least for Scale, under Possible Issues.

Graphics3D[Rotate[Scale[Ball[], {1, .7, .4}], 0.6, {0, 1, 2/3}]] // DiscretizeGraphics

EmptyRegion[3]

I cannot use Scale and Rotate after discretizing.

Rotate[Scale[DiscretizeRegion@Ball[], {1, .7, .4}], 0.6, {0, 1, 2/3}]  (* fail *)

GeometricTransformation[DiscretizeRegion @ Ball[], ScalingTransform[{1, .7, .4}]]

I am using version 10.1.

I think your last line is not correct. It should be like this: DiscretizeRegion@ TransformedRegion[Ball[], ScalingTransform[{1, .7, .4}]]. GeometricTransformation is meant to be applied to graphics primitives. The equivalent for (mesh) regions would be TransformedRegion. — Szabolcs, Mar 19 '19 at 12:17
@Szabolcs Ah, TransformedRegion !! That's what I was forgetting. LOL. Thanks for working faster than my own brain. :D — Mr.Wizard♦, Mar 19 '19 at 12:18

Mr.Wizard · Accepted Answer · 2019-03-19 12:24:12Z

2

Thanks to Szabolcs for jogging my failing memory; I couldn't remember TransformedRegion.

Fold[TransformedRegion, Ball[],
 {ScalingTransform[{1, .7, .4}], RotationTransform[0.6, {0, 1, 2/3}]}
]

% // DiscretizeRegion

Ellipsoid[{0., 0., 0.}, {{0.764563, 0.119337, -0.334044}, {0.119337, 
   0.537886, -0.0984315}, {-0.334044, -0.0984315, 0.347551}}]

answered Mar 19 '19 at 12:24

community wiki

1

$\begingroup$ You can also use Composition on transformation functions to obtain a single transformation. $\endgroup$ – Szabolcs Mar 19 '19 at 13:27

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