The link above uses processing to explore terrains using a camera and raytracing setup to render the image . You are able to choose from a number of terrains that you would like to see. Using your mouse you can look around and using the arrows on the keyboard you can move . If you press “c” you can make clouds appear and you can press “h” for high quality mode. Here is a picture of the terrain that I explored.
If you would like more information on terrain rahymarching, this link below shows the process Inigo Quilez went through and some of his codes.