Add some documentation about @markusnagel's utils.

Author: lucasb-eyer

README.md

@@ -67,6 +67,16 @@ probabilities `py`, don't forget to `U = -np.log(py)` them.
 Requiring the `reshape` on the unary is an API wart that I'd like to fix, but
 don't know how to without introducing an explicit dependency on numpy.
 
+### Getting a Unary
+
+There's two common ways of getting unary potentials:
+
+1. From a hard labeling generated by a human or some other processing.
+   This case is covered by `from pydensecrf.utils import compute_unary`.
+
+2. From a probability distribution computed by, e.g. the softmax output of a
+   deep network. For this, see `from pydensecrf.utils import softmax_to_unary`.
+
 Pairwise potentials
 -------------------
 
@@ -165,6 +175,14 @@ arguments just like in the 2D gaussian and bilateral cases.
 
 The potential will be computed as `w*exp(-0.5 * |f_i - f_j|^2)`.
 
+### Pairwise potentials for N-D
+
+User @markusnagel has written a couple numpy-functions generalizing the two
+classic 2-D image pairwise potentials (gaussian and bilateral) to an arbitrary
+number of dimensions: `create_pairwise_gaussian` and `create_pairwise_bilateral`.
+You can access them as `from pydensecrf.utils import create_pairwise_gaussian`
+and then have a look at their docstring to see how to use them.
+
 Learning
 --------