Bug report #19615
Concave hull fails for some input data
| Status: | Open | ||
|---|---|---|---|
| Priority: | Normal | ||
| Assignee: | - | ||
| Category: | Processing/QGIS | ||
| Affected QGIS version: | 3.3(master) | Regression?: | No |
| Operating System: | Windows 10 | Easy fix?: | No |
| Pull Request or Patch supplied: | No | Resolution: | |
| Crashes QGIS or corrupts data: | No | Copied to github as #: | 27442 |
Description
Concave hull fails for certain input data. It seems that when there are a limited number of points and two of them are on or close to a straight line, the algorithm fails when threshold is not 1. The attached image shows the pink hull as the output for threshold = 1, and the brown hull when threshold is between 0.96 and 0.99. For anything less than 0.96 it fails with the message below. I have attached a project with sample data demonstrating the issue.
Processing algorithm…
Algorithm 'Concave hull' starting…
Input parameters: { 'ALPHA' : 0.3, 'HOLES' : True, 'INPUT' : 'C:/Users/rudi/Dropbox/GIS/shared/concave_hull_test/input.shp', 'NO_MULTIGEOMETRY' : False, 'OUTPUT' : 'memory:' }Creating Delaunay triangles…
Results: {'OUTPUT': 'output_d516bb08_2edb_46c0_9204_cfa079c0462d'}
Computing edges max length…
Removing features…
Dissolving Delaunay triangles…
Feature could not be written to output_40dd6fbb_5c35_42aa_9c35_436e07335e57
Results: {'OUTPUT': 'output_40dd6fbb_5c35_42aa_9c35_436e07335e57'}
Saving data…
Execution completed in 0.08 seconds
Results: {'OUTPUT': 'output_6fcbb10c_d7fe_48e2_b01e_0f93f29f3b64'}Loading resulting layers
Algorithm 'Concave hull' finished
QGIS 2.18 also had the same behaviour, although it did include the following exception information:
Uncaught error while executing algorithm
Traceback (most recent call last):
File "C:/OSGeo4W64/apps/qgis-ltr/./python/plugins\processing\core\GeoAlgorithm.py", line 203, in execute
self.processAlgorithm(progress)
File "C:/OSGeo4W64/apps/qgis-ltr/./python/plugins\processing\algs\qgis\Dissolve.py", line 125, in processAlgorithm
outFeat.setAttributes(attrs)
UnboundLocalError: local variable 'attrs' referenced before assignment
