picker.raycastTerrain error

[fzw2408]

hi felixpalmer:
1,this is a great repo ,thanks you let us learning from this repo
2. i have same confuse above that maybe that is a error so i issue it
3. i try add three object into the sence, the obj's location must be {x,y,z} in sence 。 i want to picker from GPU renders Terrain's {x,y,z} .and than obj could real create on the terrain.