some minor gfx changes

some minor tex changes

tex/chapters/grid.tex

@@ -290,6 +290,8 @@
 			%
 			Hereafter, the simple transition \refeq{eq:transSimple} is combined with a second probability,
 			downvoting all grid-steps that depart from $\pathRef$.
+			To still allow leaving the shortest path, the intensity of the downvoting is controlled via $\mUsePath$,
+			with $0 < \mUsePath < 1$.
 			Finally, \refeq{eq:transShortestPath} provides a metric tending towards the reference while
 			still allowing the pedestrian to leave the shortest path:
 			%