This is NOT an Instructable on how to create a lithophane using Blender from scratch, it is simply instructions on how use the .blend file found in this Instructable to create your own lithophane.
I am assuming you have some basic Blender skills to be able to use this file, if not I STRONGLY recommend you do some basic tutorials.
Step 1: First Things First...
First download this .blend file.
Be sure to keep a copy, just in case you mess something up.
I am by no means a Blender expert, in fact I'm still quite the noob.
This file is really quite basic and I'm sure there is much better ways of accomplishing the final result, but this method works quite well!
Although I created this file from scratch, I followed other tutorials scattered around the Internet to create it.
This file was created using Blender version 2.79 on Linux, it will work on Windows and Mac OSX as long as your Blender version is the same or higher than 2.79.
Step 2: Have a Look Around...
Once you open the file zoom in and rotate the view a bit, you'll notice the image is not flat, it's actually 3 dimensional. This is the magic of a lithophane. When 3D printed and placed in front of a light source, the raised parts allow less light through creating darker tones, and the lower sections allow more light through showing lighter tones, this gives the sense of a black and white photo.
To view the model with the actual image overlayed on the model, click the button shown in the above image and choose "Material", this is not necessary but helps you better visualize what you're trying to achieve.
Step 3: Apply Your Image
The object "LithoMOD" does all the fun stuff. Select it and go to it's Texture tab. Make sure "Displace" is active and then remove the image "grub_background.png" by clicking the "X". This is important as it's embedded in the file and must be removed. Now click "Open" and select the image you want to turn into a lithophane.
At this point go back to "Solid" view (see previous step) to see the model without the image overlay. You should see your image "embossed" onto the model.
Step 4: Better Visualizing Your Image
If you want to overlay your image with the model you can do this from the Material tab. First delete the current image in the "Image Texture" box, then click "Open" and select your image again.
You can then go back to "Material" view and see the image overlayed on the model.
I recommend you work mostly in "Solid" view as it's easier to see the actual model that will be printed, although it's fun to see the image on the 3D model using "Material" view!
Step 5: Modifiers (The Fun Bit!)
To change the look, shape and depth of your new lithophane you need to change the modifiers in the "Modifiers" tab.
Start by selecting the object "LithoMOD" and go to it's "Modifiers" tab.
The first modifier gives the lithophane it's curve, the only thing you need to change here is "Angle". The objects "LithoBack" and "Support" will follow this angle, but you can only go up to about 120°, after that they kind of get out of sync. You can play around the object "BackEmpty" and try scaling the objects, but that' won't be discussed here. After changing the angle it will not update automatically, there are many ways to do an update but the easiest is to select the object "LithoBack" in the graphics window, press TAB to enter edit mode and then press TAB again to exit, this will force the model to update.
The next modifier is called "Multires", all this does is adds resolution to the final model, in other words, the higher the Multires factor the finer the detail in the resulting STL you create. Higher factors do however create much larger STL files. For example, I use 5 as a good amount of detail verses the file size. The file size with a factor of 5 results in a file around 200Mb, simply changing to a factor of 6 creates a file around 800Mb! You have been warned! The only factor to change here is "Preview" as it's the only one that will change the file you produce.
Lastly, and most importantly, is the "displace" modifier. This is what maps the image to the models surface creating the actual 3 dimensional part. Here the 2 settings to change are "Midlevel" and "Strength". Midlevel will effectively move the model in and out changing the distance from the object "LithoBack". The further away it is the darker your lithophane will be. Strength will change the distance from the highest point to the lowest point giving the lithophane it's difference between light and dark tones.
These modifiers are what you want to play around with the most, try different settings, experiment, discover what works best for the image you use. What I have set as default work very well for most images, you will probably only need to change the angle in the Deform modifier to suit your application and get a good result!
Step 6: Save the STL
Once you are happy with the way you have set up the model it's time to output to an STL file.
Select the objects "LithoMOD", "LithoBack" and "Support" then click File-->Export-->Stl.
In the save window give it a name and an appropriate location to save it.
The most important thing here is to turn on "Selection Only". This makes sure that only the parts you selected earlier get saved to the STL. Ensure "Apply Modifiers" is also on.
Step 7: Slice and Print!
The STL file you created in the last step should be around 200Mb, if it's considerably larger some slicing programs might struggle with it. Cura is my choice for slicing but use what you know. There are many tutorials out there about how to set good slicing settings, so I'm not going to go into that here, and all printers are different so you will have to learn what works best for you. Just be sure to use a large brim.
After the file is loaded into your slicer be aware that if you choose to scale it down the gap between the lithophane and the supports will be reduced. There gap is only 0.2mm so scaling down much lower than 80% might cause them to fuse with the lithophane too much making them impossible to remove. Also, if you scale up too much the gap will be too great making them useless.
If you want to scale down you can always simply not select the supports when exporting the STL in the previous step. they are there for a reason and work quite well so only remove them if you want to scale down below 50%.