Package .vtk files in a single scene

[da-crivelli]

The idea is to be able to open a single ParaVIEW collection that includes all of the result meshes.

See the following code suggested by Lufthschraube on the FreeCAD forums:

PVUFile = open(ExportOutputPath + "/" + FileName + ".pvd","w")
	PVUFile.write("<VTKFile type=\"Collection\" version=\"1.0\" byte_order=\"LittleEndian\" header_type=\"UInt64\">\n\t<Collection>\n")
	
	n = 0
	for ExportObject in sorted(FEMResultObjects):
		n = n + 1
		
		#Read and format time stamp (e.g., 12.37 s = 0001237)
		FreeCADResultLabelParts = ExportObject.split("_")
		PreDecimal = FreeCADResultLabelParts[-3]
		PostDecimal = FreeCADResultLabelParts[-2]

		if len(PostDecimal) == 1:
			PostDecimal = PostDecimal + str(0)
		TimeValue = float(PreDecimal) + float(PostDecimal)/100
		TimeString = str(int(round(TimeValue*100,0))).zfill(7)
	
		#For some reason, the VTK exporter expects a list (although only one object is processed at once...) - so build a list with the current object
		ExportObjectList = []
		ExportObjectList.append(FreeCAD.ActiveDocument.getObject(ExportObject))
		FileNameOUT = FileName + "_" + TimeString + ".vtu"
		FilePath = ExportOutputPath + "/" + FileNameOUT
		FreeCAD.Console.PrintMessage(FilePath + " is to be created\n")
		feminout.importVTKResults.export(ExportObjectList,FilePath)
	
		PVUFile.write("\t\t<DataSet timestep=\"" + str(TimeValue) + "\" file=\"" + FileNameOUT + "\"/>\n")
	
	#Close the .pvu file
	PVUFile.write("\t</Collection>\n</VTKFile>")
	PVUFile.close()