"Discussion of some of the relationships between (a) predicting physical, topological and geometrical consequences of motions and (b) predicting the changes in affordances that result from such motions, including both (b.1.) changes in action affordances (changes in what the agent can do in the environment) and (b.2.) changes in epistemic affordances, i.e. changes in the information available to the agent or changes in the ease of planning or deciding. It is suggested that in some circumstances the predictions can be based on processes operating on selected fragments of a 2-D representation of a 3-D scene (or a 2.5-D representation when occlusion is involved) and reasoning by manipulating the representation. Moreover, where uncertainty is a problem for prediction it is often due to the existence of a ''phase boundary'' between configurations where the prediction definitely gives one result and configurations where the prediction definitely gives another result. One way of reducing uncertainty is move an object (or even the viewing position) away from such a phase boundary. This sometimes allows simple, deterministic, geometric reasoning to be used, instead of much more complex and unreliable reasoning with probability distributions and expected utilities." (http://www.cognitivesystems.org/cosybook/chap12.asp) (http://www.cs.bham.ac.uk/research/projects/cosy/papers/changing-affordances.html)