catapult game

Hi all,

I am trying to make a catapult game ( like the one in flash, you load a cat or any character and shoot , if it hits certain thing in reacts to them, like a tree or explosive, a cactus a spring , etc)

I have a cannon that i can rorate up down and side to side and I can add power for the hit..and it instantiate the character and add the correct amount of force.(I use rigidobject.addforce)

so my issue is I am using a terrain : i want it to be mud, stones, grass, trees , how can i check for collision?

I saw something terrain data and splat something, they made me dizzy ... is there an easier way -basically I want to know what does the cat (projectle hit) and makes it react to it