3DP Rocks (opens in a new tab) is a lithophane creation tool.
3DP Rocks is a simple, drag-and-drop tool that allows you to turn images into 3D lithophanes which can then be edited or printed. Te Wāhi has it's own 3DP instance online which is free and without ads, and can be run on any device with a web browser.
The homepage shows a choice of different lithophane templates that you can choose from.
Clicking on the Images tab, then dragging and dropping an image will start the conversion process. It is best to use images with a high contrast/difference between light and dark tones.
Clicking on the image will load it into a model template, which can be viewed by going back to the tab.
From here, you can choose different template shapes. Click Refresh once you have selected a different template to load it in.
When you are ready, click Download and your lithophane will save as a STL file ready to print.