Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
Starting from any of the 2D generated graphics, from the other answers, as a Rasterized Image, hereafter named g2d:
Image3D[{g2dRasterize[g2d]}, BoxRatios -> 1] 
and a lot of tweaking is possible with the Image3D options.
Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
Starting from any of the 2D generated graphics, from the other answers, as a Rasterized Image, hereafter named g2d:
Image3D[{g2d}, BoxRatios -> 1]
and a lot of tweaking is possible with the Image3D options.
Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
Starting from any of the 2D generated graphics, from the other answers, hereafter named g2d:
Image3D[{Rasterize[g2d]}, BoxRatios -> 1]
and a lot of tweaking is possible with the Image3D options.
Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
(starting Starting from any of the 2D generated imagesgraphics, from the other answers, as a Rasterized Image, hereafter named g2d):
Image3D[{g2d}, BoxRatios -> 1]
and a lot of tweaking is possible with the Image3D options.
Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
(starting from any of the 2D generated images from the other answers, hereafter named g2d)
Image3D[{g2d}, BoxRatios -> 1]
and a lot of tweaking is possible with the Image3D options.
Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
Starting from any of the 2D generated graphics, from the other answers, as a Rasterized Image, hereafter named g2d:
Image3D[{g2d}, BoxRatios -> 1]
and a lot of tweaking is possible with the Image3D options.
Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
(starting from any of the 2D generated images from the other answers, hereafter named g2d)
Image3D[{g2d, g2d}, BoxRatios -> {1, 1, 1}]1]
and a lot of tweaking is possible with the Image3D options.
Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
(starting from any of the 2D generated images from the other answers, hereafter named g2d)
Image3D[{g2d, g2d}, BoxRatios -> {1, 1, 1}]
and a lot of tweaking is possible with the Image3D options.
Although I think that some of the options presented on the other answers are better, this one is probably the one with the shortest code on the 3D aspect:
(starting from any of the 2D generated images from the other answers, hereafter named g2d)
Image3D[{g2d}, BoxRatios -> 1]
and a lot of tweaking is possible with the Image3D options.