Stencil: use better examples in documentation comment

include/user/stencil.h

@@ -16,14 +16,14 @@ namespace cologex {
  * allows the stimbufflib driver to describe the subset of the input data that
  * is relevant to SMO. For example:
  *
- * * A HSB format camera might treat brightness values above 128 as
- *   negtrins, creating a Stencil that denotes all offsets in a
- *   frame that exceed 128.
- *
  * * A lidar yielding XYZI[ntensity] might consider I values exceeding 128 to be
  *   negtrins, creating a Stencil listing all values in the point
  *   cloud that exceed 128.
  *
+ * * A lidar that extracts ambience might consider ambience counts below a
+ *	 threshold to be postrins -- i.e, it incentivizes the agent to prefer
+ *	 darker environments.
+ *
  * The Stencil internally represents offsets with ranges or other efficient
  * formats to describe offsets (e.g., by row). The internal format is opaque to
  * the stimbufflib, which describes relevant ranges by calling Stencil methods.