DOC: doc update for MeanShiftSegmentationFilter.

Code/OBIA/otbMeanShiftSegmentationFilter.h

@@ -79,7 +79,8 @@ private:
 *
 *  Performs segmentation of an image by chaining a mean shift filter and region
 *  merging filter.
-*
+*  This filter relies on MeanShift Labeled image created from clustered filtered output of meanshift filter.
+*  Mode search algorithm is not performed on tiles boundaries. Thus output depends on Thread numbers.
 */