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Why these errors with DiscretizeGraphics and "Undefined" for Volume?

Posted 4 years ago

A list of x,y coordinate pairs generates a ListLinePlot and Interpolation of the pair list creates a curve that can be rotated about the x-axis by RevolutionPlot3D. DiscretizeGraphics then generates what appears to be the correct meshed surface, but with a series of error messages about the values of PlotRange? I want the surface area of the resulting body, which is correctly given by Area, but Volume returns "Undefined"?

POSTED BY: Kevin Ulmer
5 Replies

It is probably not defined because the resulting region is a surface rather than a filled body.

POSTED BY: Sander Huisman
Posted 4 years ago

Is there a simple call to convert a surface to the enclosed solid?

POSTED BY: Kevin Ulmer
POSTED BY: Henrik Schachner
Posted 4 years ago

Hi Kevin,

Not sure why Volume does not work, perhaps because the discretization has some imperfections. You could just use calculus

Area of surface of revolution about the x axis

2 Pi NIntegrate[curve[x] Sqrt[1 + D[curve[x], x]^2], {x, 0, 108}]
(* 4048.33 *)

Volume

NIntegrate[Pi curve[x]^2, {x, 0, 108}]
(* 13122.5 *)
POSTED BY: Rohit Namjoshi
Posted 4 years ago

Yes, I've done the integral separately. Not a very informative error message. Thanks!

POSTED BY: Kevin Ulmer
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