Adjust decimation step for cropping, catch edge case where convex hull is obliterated

opendm/cropper.py

@@ -189,8 +189,14 @@ class Cropper:
         BUFFER_SMOOTH_DISTANCE = 3
 
         if buffer_distance > 0:
-            convexhull = convexhull.Buffer(-(buffer_distance + BUFFER_SMOOTH_DISTANCE))
-            convexhull = convexhull.Buffer(BUFFER_SMOOTH_DISTANCE)
+            # For small areas, check that buffering doesn't obliterate 
+            # our hull
+            tmp = convexhull.Buffer(-(buffer_distance + BUFFER_SMOOTH_DISTANCE))
+            tmp = tmp.Buffer(BUFFER_SMOOTH_DISTANCE)
+            if tmp.Area() > 0:
+                convexhull = tmp
+            else:
+                log.ODM_WARNING("Very small crop area detected, we will not smooth it.")
 
         # Save to a new file
         bounds_geojson_path = self.path('bounds.geojson')

stages/odm_georeferencing.py

@@ -120,7 +120,12 @@ class ODMGeoreferencingStage(types.ODM_Stage):
                         log.ODM_INFO("Calculating cropping area and generating bounds shapefile from point cloud")
                         cropper = Cropper(tree.odm_georeferencing, 'odm_georeferenced_model')
                         
-                        decimation_step = 40 if args.fast_orthophoto or args.use_opensfm_dense else 90
+                        if args.fast_orthophoto:
+                            decimation_step = 10
+                        elif args.use_opensfm_dense:
+                            decimation_step = 40
+                        else:
+                            decimation_step = 90
                         
                         # More aggressive decimation for large datasets
                         if not args.fast_orthophoto: