I got this idea when I saw some cool videos on YouTube with tesselation and displacement. I began to think about how I could utilise this method in other ways. I soon got the idea to create a material which could extrude stalactites in a cave environment. After some more researching I found out that I could incorporate vertex paint into the material. This made it possible for me to draw out exactly where I wanted the stalactites to go using the Mesh Paint Tool in UDK.
I used a tiled heightmap to form the stalactites how I wanted them. To stop the user from drawing out stalactites on the walls I based the stalactite material on a down vector blend.