Most common tree toppers designs are in the shape of a star, but yours can be what ever shape you desire! We used our Adafruit logo for the base shape. Do a bit of googling to find images of tree toppers for inspiration, there are so many! For more homework, why not explore the thingiverse site for ideas that have been printed.
We used illustrator to create the Adafruit logo, but you can any use any freeware open sourced vector art programs. It's best to use a solid shape and avoid complex patterns that might be too small to make on a 3D printer. Our Adafruit logo has five holes in the center that is simple enough to turn into an extruded shape.
In Autodesk 123D Design web app, import your SVG by selecting "Import" under the file menu (or command+shift+i). Your shape will load into the scene with the option to resize the dimensions. You must click on the grid layout to accept and load the shape.
Once you click, you should see arrow handles appear on the shape. These allow you to move the object around in the grid. Use a measuring tool to determine the overall size of your tree topper. If you have a reference topper handy, measure the dimensions and compare it to the max build size of your 3D printer (make it as big as you can!). You can resize the shape at any time by selecting the object and changing the input values at the bottom of the UI. Use the "lock" icon to scale proportionately.
Once you have resized your shape to your desired measurements, save your project. With your design named and saved, goto the top right and click on your username. Select "My Projects" and then click on the "Models" link in the left sidebar. Locate your design and click on the thumbnail. Click the big blue Edit/Download button and select "Download 3D Models" from the drop down. Check the .smb file and select "Download Models" (you won't need the STL or recipe files).
Withe the app downloaded, click open and select the "browse my computer" tab to navigate to your downloaded design (the .smb file). Select your design to open it. The desktop app is similar to the web app but different in terms of boolean operations (combining and subtracting shapes versus object types like solids and voids). We found the current web app to be a bit slower and unstable at times but feel free to test both of them out and see which one works for you.
Once you have the shape loaded and set to your desired measurements, you will need to make a duplicate of the shape and move it down and out of the way for now (don't delete this, you will need it for creating the cover) Extrude the shape so its thick enough to create a shell and hollow it out. To extrude, click on the shape to select it and then click once more on the top face. It should highlight blue. A gear icon will appear close to the object. Click on the gear icon and select the Press/Pull option. Enter the your desired distance for the height of the object. Test and see how thick you want your tree topper to be. Since you will be using NeoPixel strips inside the shape, it should be at least 12mm thick (Our tree topper is 20mm thick).
With your shape extruded to the desired thickness, click on the object to select it and then click on the top face to highlight it blue again. Click on the gear icon and choose the shell option. A new options menu will appear at the bottom of the screen. Put the value "1" in the input box of the Thickness Inside option. Click on an empty space in the grid to accept or hit enter to complete the shell function.
In our shape, we have undesired edges that were created during the shelling process. We can easily remove these sharp edges by subtracting with a few shapes. Simple cylinders can be added and subtracted to the shape by using the combine function. We used a total of 5 new cylinders to cut of our unwanted edges. This step is optional if your shape is simple and doesn't have any unwanted edges. Once you have your desired shell, now is a good time to save it!
Move the duplicated base shape back to your work area. You will need to create 2 more duplicates (a total of 3 base shapes) to create a snap on cover. We need to make an inner edge on the cover so it can snap to the inside of the shell we created. To do this, we will create a shell out of one of the duplicates. Use a thickness of 1.3mm.
In our shape, we had to fill in the five holes that are in the center of our shape because we were having issues removing the access edges. We moved simple cubes to the holes and merged them to the duplicates to create a solid shape. This step is optional if you have a simple shape with no cut outs.