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Bug persisting in 11.3


A 3D disk Region placed at {1,0,0} visualizes correctly:

Region[ParametricRegion[{{1,0,0} + r { Cos[a], Sin[a], 0}, 
   0 <= r <= 1 && 0 <= a <= 2 Pi}, {a, r}]]

But when using a MachinePrecision number {1.,0,0} only half of the disk gets visualized:

Region[ParametricRegion[{{1.,0, 0} + r { Cos[a], Sin[a], 0}, 
       0 <= r <= 1 && 0 <= a <= 2 Pi}, {a, r}]]

Exchanging the independent variables {r,a} corrects the behavior:

Region[ParametricRegion[{{1., 0, 0} + r { Cos[a], Sin[a], 0}, 
   0 <= r <= 1 && 0 <= a <= 2 Pi}, {r, a}]]

Need the independent variables be ordered in a specific way? If so why?

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This is a bug in the visualization code in Region, but all the properties of the ParametricRegion itself are OK. For example, if you compute the Area of the two regions, both will give 3.14.... If you haven't already done so, please report this as a bug in Region to support.

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