A couple of ways of doing this in 3DC without importing vector shapes though not as elegant as Geormagic. You might know these ways already.
All methods done in Ortho Mode.
Use the Clay Brush, as it has Options to select in it's Tool Panel. Test how each work and also adjusting the "BorderFormParam" Important, learn how these work.
Closed Spline tool or another one plus you will use the Pose tool last. Change border width if necessary in the E-Panel.
Select an axis and draw the spline in empty space.
Depth 100% This will give you enough material to use the pose tool with. I wish you could set it higher and it would extrude that amount but alas nope... (feature request maybe)
Press enter and the shape is created.
Change the axis and use the pose tool to select at least half or more of the voxel object.
Under the pose tool panel select "Align to View" the transform gizmo will line up correcty.
Transform the shape out to the distance you desire.
Use Clay Brush again.
Closed Spline Tool or another spline tool.
Draw the Spline over the area on a primitive (used as a voxel base) to create your shape from.
Now hold down the Shift and Ctrl keys and press enter it will cut away the outside and leave the shape that you created. Holding down only the Ctrl key cuts inside the shape leaving the shape's hole in the voxel model.
Again you can use the pose tool if necessary or the cut off tool to get the correct distance.
Note: You will need to deselect "Ignore Back Faces" in the E-Panel for the pose tool to grab all the way though the voxel object, also deselect it for the clay brush.
Learn the ins and outs of the Close Spine tool... You have 3 types of points, right click on a point to see the change. check the tool panel as well for more options.
You can add more points after hitting the escape key by hovering over an empty spot on the spline and when the cursor turns green you can add a point plus move your points as well.
Short of making a video tutorial and AbnRanger might have one already, did not check, test out these methods and remember I did not say it was as
elegant as Geormagic
In the picture: Left Side shape created with the first Method. Right side, shape created with second method.
EDIT: I tested a few things and found the the Blob brush gives more thickness at 100% than the carve brush and you have the same tool panel options but you lose the ability to cut away like the crave brush...
EDIT 2: I tested the Clay brush and it does everything the carve brush does but give more thickness at 100% I changed the post above to using the clay brush.