If i have an object, and i place it on top of a bumpy surface, is there a way to align the objects bottom surface angle with the floor surface angle?
nvm, already found something: the snap tools…
You can select your object (in object mode) and then enable snapping/to faces/align rotation with snapping target.
Now use the “g” key to move the object in the proximity of the surface… it may jump around a little but it will align itself with the surface. If you find it’s going above or below the surface slightly you can tweak by using the manipulator widget and move it into place.
Important do the initial placement by using “g” and not the manipulator or else it won’t rotate.
Here’s a blend example. http://www.pasteall.org/blend/4485