To generate our 3D model, we will use the Lithophanes application. You can however use Cura to do it, most of these instructions will still apply.

In the "Imagem" tab (the only thing left untranslated), we select Open Image and select our image. It will load the image and display in the main window, we will then be able to adjust the various settings of the image, such as Contrast, Brightness and Gamma.

There is also a Binarize option which can be helpful if you want a purely black or white lithophane (no shades of grey). Note that if you use the Binarize option, then the Contrast, Brightness and Gamma options are ignored.

There is also a button for displaying the Negative of the image, and finally a Restore button to reset everything back the way it was.

The Max proportion in Pixels is an important setting, as it allows you to select between a down-sampling of the image to 500 or 1000 pixels. Usually 500 pixels is more than enough. You will usually want to have a maximum of 1 pixel for each half width of your nozzle.

This means that if you have a nozzle of 0.5 mm and you want to print a lithophane of 100 mm width, then you need less than 400 pixels:

100 / (0.5 / 2) = 100 / 0.25 = 400 pixels

If however you have a 0.35 mm nozzle (like me) and you want to print a lithophane of 150 mm or 200 mm, then you will need :

150 / (0.4 / 2) = 150 / 0.2 = 750 pixels 200 / 0.2 = 1000 pixels

If you have a very small nozzle or/and want to print a large lithophane, then using 1000 pixels might give you a slight increase in quality, otherwise 500 is more than enough. Note however that the higher the resolution, the longer it will take to slice the model. Actually, using 1000 pixels on my sample images dramatically increase the slicing time making it go from a couple of minutes to an overnight task (more on that later) so you may always want to keep it at 500 regardless of nozzle size and length.

Once you have an image to your liking, go to the "3D - STL" tab where you can set your parameters for how the lithophane should be printed. I think the default options here are pretty good (see image).

Width (mm): This is the width of the lithophane, it will be tied to the Height parameter so the aspect ratio is always kept Height (mm): This the the height of the lithophane, it will be tied to the Width parameter so the aspect ratio is always kept Z (mm): This is the Z depth of the lithophane. Thickness (mm): This is the thickness of the base. Edge (mm): This creates a boxed frame around the lithophane.

The Z and Thickness parameters are the most important here. The bigger you set the value of Z, the more shades of grey you will be able to have, but if you set it too high, then the lithophane will be too dark to show its full effect with a back light, and it will increase the print time considerably. The default here is 2 mm and I think it's a pretty good value but you may want to increase it to 5 mm for a more detailed print (the higher the number, the longer it will take to print though, if you're inpatient, 2 mm might be good enough for you). The Thickness parameter however will need to be as small as possible, so it doesn't block any light and doesn't affect your lithophane. So it can be sliced into a single layer, the best value here is your first layer height in your slicing software. The default is 0.25 (note that due to brazilian locale, you need to use a comma as a decimal separator: "0,25" instead of "0.25") which is what most people have. If your slicing software sets the first layer height to 0.3 or 0.35 for example, then change that value accordingly. If however, your photo has white areas, you might end up with some areas where only the first layer is visible and it would look too bright and the infill lines would show through, in that case, you can increase it to 0.5 mm for example. You can also adjust it depending on how dark you want the overall picture to look.

While the Width/Height parameters are self explanatory, it is a good moment to point out that for best results, a print of 100x100 mm in size (or close to it, depending on the picture's aspect ratio) is a good trade-off between print time and print details. Obviously, the bigger the print, the more detailed it will be, however, it can take a long time to print. You can print smaller 50x50 mm lithophanes as well or lower for low-detailed prints.

Finally, the Edge parameter can be left at the default of 0, but I personally like adding a 1 mm or 2 mm frame around the print.

You can click the Generate 3d button to see how each parameter affects the print until you are satisfied, then click the Save STL button to save your 3D model to an STL file. Make sure you wait until the status bar says "File Save" before you load the STL in your slicing program.