Launch:
- Download the zip from here, unzip it
- Start unity hub.
- In the menu with projects click ADD
- Select the unzipped folder.
- If the scene is empty at startup, click on SampleScene in the Project menu.
- At the top of the editing window there is a button to switch off the grid if it gets in the way.
The main code you can play with is in RayMarching.shader from 31 to 133 lines, the rest is auxiliary to make the shaders work properly with Unity camera.