another-take…

tetrahedron.geo
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			lc = 1;
			h = 1;

			Point(1) = {lc, lc, lc, h};

			line[] = Extrude{-2*lc,0,0}{ Point{1}; };
			surface[] = Extrude{0,-2*lc,0}{ Line{line[1]}; };
			volume[] = Extrude{0,0,-2*lc}{ Surface{surface[1]}; };

			Physical Volume(1) = {volume[1]};

			Transfinite Surface "*";
			Transfinite Volume "*";