# Cannot DiscretizeGraphics[] Parallelepiped nor Hexahedron

par = Parallelepiped[{-250, 400,400}, {{0, 0, 0}, {0, -500, 0}, {7050, 0, 2763}}];
hex = Hexahedron[{{-250., 400., 400.}, {-250., 400., 400.}, {-250.,900., 400.}, {-250., 900., 400.}, {6800., 400., 3164.}, {6800., 400., 3164.}, {6800., 900., 3164.}, {6800., 900., 3164.}}];

grapar=Graphics3D[par];
DiscretizeGraphics[grapar, MaxCellMeasure -> 0.3]


(*I don't know why the DiscretizeGraphics don't work. From the wolfram reference website, Parallelepiped and Hexahedron belong to "Bounded piecewise linear primitives in Graphics3D (these can be represented exactly)" The error shows: DiscretizeGraphics::invprim: The graphics primitive Parallelepiped[{-250.,400.,400.},{{1.10^-17,-4.5474710^-13,1.*10^-17},{1.*10^-17,-500.,1.10^-17},{7050.,-5.6843410^-13,2763.}}] is not valid.

If anyone can help, I will really appreciate~ I would like to export it into stl. at the end, so I think this discretize step is necessary. Thank you!

*)

We can directly use Polygon.

p = {-250, 400, 400};
v1 = {0, -500, 0};
v2 = {7050, 0, 2763};
reg = Polygon[{p, p + v1, p + v1 + v2, p + v2}];
dreg = DiscretizeRegion[reg]
Export["test.stl", dreg]
Import["test.stl"]


If we change the order of the points of hex, Polygon also work.

pts = {{-250., 400., 400.}, {-250., 400., 400.}, {-250., 900.,
400.}, {-250., 900., 400.}, {6800., 900., 3164.}, {6800., 900.,
3164.}, {6800., 400., 3164.}, {6800., 400., 3164.}};
Export["test.stl", Polygon[pts]]
Import["test.stl"]