document the aspect ratio filter

src/aspect_ratio_filter.h

@@ -6,6 +6,12 @@
 #include <vtkIdList.h>
 
 
+/*
+  Computes the worst triangle aspect ratio for each cell and stores it
+  in a "aspect_ratio", 1 float cell data array. Requires the input to
+  have an "angles", 12 float cell data array containing the angles of
+  every triangle for each cell, grouped by triangle.
+*/
 class AspectRatioFilter : public vtkUnstructuredGridAlgorithm {
 public:
 	static AspectRatioFilter *New();