The Infinity Heart Ornament is a heart when viewed from the front and an infinity when viewed from the top. When the lighting is right you can see both at once with the object and it's shadow. And there's a surprise in the design's third dimension
Step 1: Draw a Heart
Draw a heart on one plane
There are many ways to do this; this heart started as a circle. I viewed the points on the circle, added extra points to the circle, and moved individual points to create a heart.
Step 2: Edit the Points in 3 Dimensions Into an Infinity Heart Shaped Curve
Edit the points in 3 dimensions into an infinity heart shape.
Moment of Inspiration Software (MOI) is used here to edit a flat curve into a 3d curve. Not all software has this feature.
Step 3: Draw a Small Circle Next to the Infinity Heart Curve
Draw a small circle next to the Infinity Heart curve.
Step 4: Sweep the Circle Along the Infinity Heart Curve
Sweep the circle along the Infinity Heart curve.
Set the small circle as the profile and the infinity heart curve as the path to create an object.
Step 5: View From Each Direction
View the results from each direction.
A heart in one direction, an infinity in another direction, as expected.
The surprise in the design is the third orientation which has a Christian fish; perfect for a Christmas ornament.
Step 6: Add an Oval Torus to Hang
Add an oval torus to hang, because a hook didn't look as pretty.
Step 7: Export the STL File
Export the STL file to be 3D printed.
Step 8: Analyze & Fix Problem Spots
Analyze & Fix problem spots in Autodesk Meshmixer.
User Analysis button, then the Inspector option from the menu. The software will highlight any problem areas and give you an opportunity to repair before saving and printing.
If you haven't got a printer, you can save an STL file and upload to Shapeways.com or one of the other service bureaus to have the object printed.
Step 9: 3D Print
Step 10: Remove the Support Material
This geometry is not robust enough to print without support material; so your print will have extra material to cut away.