0003617: FEM, post processing, vtk mesh, it is not possible to create a vtk mesh with gaps - FreeCAD Tracker

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ID	Project	Category	View Status	Date Submitted	Last Update

0003617	FEM	Bug	public	2018-09-25 21:30	2019-01-14 18:37

Reporter	berndhahnebach	Assigned To	ickby
Priority	normal	Severity	major	Reproducibility	always
Status	closed	Resolution	fixed
Fixed in Version	0.18

Summary	0003617: FEM, post processing, vtk mesh, it is not possible to create a vtk mesh with gaps
Description	https://forum.freecadweb.org/viewtopic.php?f=18&t=27105&start=70#p225490
Steps To Reproduce	- open FEM 2D example - select solver - change "Beam Shell Result Output 3D" to true - rerun analysis - check Abs displacement colors in standard result object, they look fine. - select the 3D solid result object - create vtk pipe - some error in report view is printed - double click on the pipeline - set mode "Surface wit edges" - set field to "Displacement" - set vector to "Magnitude" - this does not look to be the right coloring ... to reproduce by Python (tested with FreeCAD 0.18.15607) use: # load 2D example file and set 3D output in solver doc = FreeCAD.open(FreeCAD.ConfigGet("AppHomePath") + 'data/examples/FemCalculixCantilever2D.FCStd') doc.FEMMeshGmsh.ViewObject.Visibility = False doc.CalculiXccxTools.BeamShellResultOutput3D = True doc.recompute() # run the analysis import FemGui FemGui.setActiveAnalysis(doc.Analysis) from femtools import ccxtools fea = ccxtools.FemToolsCcx() fea.update_objects() fea.purge_results() fea.run() doc.Result_mesh.ViewObject.Visibility = False # create vtk result pipline import ObjectsFem ObjectsFem.makePostVtkResult(doc, doc.CalculiX_static_results) doc.recompute() doc.FEMVtkResult.ViewObject.DisplayMode = 'Surface with Edges' doc.FEMVtkResult.ViewObject.Field = 'DisplacementVectors' doc.FEMVtkResult.ViewObject.VectorMode = 'Magnitude'
Tags	No tags attached.

FreeCAD Information

berndhahnebach 2018-09-26 21:25 developer ~0011860	the code ... https://github.com/FreeCAD/FreeCAD/blob/a0ff629747d5d73567075821852a8cdaadcf51c5/src/Mod/Fem/App/FemVTKTools.cpp#L445-L462

berndhahnebach 2018-09-26 21:28 developer ~0011861 Last edited: 2018-09-26 21:29	If the FreeCAD file is saved and reopened the problem could be even worse, because of 0002873. But both are totally independent!

ickby 2019-01-03 09:21 developer ~0012363	Problem are the not continuous node ids in the freecad mesh. In general the FEM result property stores all results for the individual mesh nodes by index, assuming index==id. Hence Node 1 result is in result vector at position 1. However, when the node ids are not continuous in the freecad mesh, e.g. there are 3 nodes but ids are [0 1 5], that mapping does not work for VTK anymore. The reason is that in VTK node ids must be continuous, the example mesh would result in the following VTK nodes [0 1 2 3 4 5] with ids 2,3,4 existing but not used by any elements. Now with index==id the results would be assigned to ids [0 1 2] instead of [0 1 5], which results in the display error. The solution is to remove the assumption index==id and use the correct note id for each result value: https://github.com/ickby/FreeCAD_sf_master/commit/605edeecb2152130395177d0ae4828d6e1c4b12e @berndhahnebach Could you do some regression testing with this fix?

wmayer 2019-01-14 18:37 administrator ~0012431	https://github.com/FreeCAD/FreeCAD/commit/16435205d409353cb2a49ee65bf83031c06be4f8

Date Modified	Username	Field	Change
2018-09-25 21:30	berndhahnebach	New Issue
2018-09-25 21:30	berndhahnebach	Status	new => confirmed
2018-09-26 21:25	berndhahnebach	Note Added: 0011860
2018-09-26 21:28	berndhahnebach	Note Added: 0011861
2018-09-26 21:28	berndhahnebach	Note Edited: 0011861
2018-09-26 21:29	berndhahnebach	Note Edited: 0011861
2019-01-03 09:21	ickby	Note Added: 0012363
2019-01-11 06:21	berndhahnebach	Steps to Reproduce Updated
2019-01-11 06:58	berndhahnebach	Steps to Reproduce Updated
2019-01-11 06:59	berndhahnebach	Steps to Reproduce Updated
2019-01-14 15:43	wmayer	Relationship added	related to 0002873
2019-01-14 18:37	wmayer	Assigned To	=> ickby
2019-01-14 18:37	wmayer	Status	confirmed => closed
2019-01-14 18:37	wmayer	Resolution	open => fixed
2019-01-14 18:37	wmayer	Fixed in Version	=> 0.18
2019-01-14 18:37	wmayer	Note Added: 0012431