View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0032132 | Community | OCCT:Data Exchange | public | 2021-02-15 21:55 | 2023-01-20 13:52 |
| Reporter | geuzaine | Assigned To | |||
| Priority | normal | Severity | minor | ||
| Status | new | Resolution | open | ||
| Product Version | 7.5.0 | ||||
| Summary | 0032132: Data Exchange - STEP export duplicates surfaces, leading to non-conformal geometry | ||||
| Description | Dear OCCT team, When I import a BREP file that contains several solids that share faces, then export it as STEP, the STEP file duplicates the shared faces, leading to a non-conformal (topologically) model. I've tried the various STEP export modes, but so far without success. Is this a know issue/limitation of the STEP exporter? Thanks, Christophe | ||||
| Steps To Reproduce | Compile and run the following C++ code, which loads a BREP file (input.brep - attached to this report) and outputs both BREP (output.brep) and STEP (output.step) files :
// g++ io.cpp -I/usr/local/occt/include/opencascade -L/usr/local/occt/lib -lTKSTEP -lTKSTEP209 -lTKSTEPAttr -lTKSTEPBase -lTKXSBase -lTKShHealing -lTKTopAlgo -lTKGeomAlgo -lTKBRep -lTKGeomBase -lTKG3d -lTKG2d -lTKMath -lTKernel -lfreetype
#include <BRep_Builder.hxx>
#include <BRepTools.hxx>
#include <STEPControl_Writer.hxx>
int main()
{
TopoDS_Shape shape;
BRep_Builder builder;
BRepTools::Read(shape, "input.brep", builder);
BRepTools::Write(shape, "output.brep");
STEPControl_Writer writer;
writer.Transfer(shape, STEPControl_AsIs);
writer.Write("output.step");
return 0;
}
The output STEP file contains duplicate surfaces, while the output BREP file is correct. | ||||
| Additional information and documentation updates | See e.g. https://gitlab.onelab.info/gmsh/gmsh/-/issues/906 for a related bug report in Gmsh. | ||||
| Tags | No tags attached. | ||||
| Test case number | |||||
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input.brep (47,079 bytes) |
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Maybe parameters "write.step.nonmanifold" and "read.step.nonmanifold" might be helpful.pload XDE MODELING restore input.brep i testwritestep i1.stp i testreadstep i1.stp i1 param write.step.nonmanifold 1 param read.step.nonmanifold 1 testwritestep i2.stp i testreadstep i2.stp i2 |
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I've tried the various options listed here https://dev.opencascade.org/doc/refman/html/_s_t_e_p_control___step_model_type_8hxx.html#a032affe8dae498d429a83225f8c5da4e but none produced a file with non-duplicated faces (and some just fail). What are the C++ options that correspond to write.step.nonmanifold/read.step.nonmanifold? If there are no direct equivalents, could you attach your files i1.stp and i2.stp so I could examine them? |
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i1.stp (391,581 bytes) |
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i2.stp (268,787 bytes) |
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> What are the C++ options that correspond to write.step.nonmanifold/read.step.nonmanifold? STEP/IGES parameters are managed via Interface_Static interface (exposed by "param" command in Draw Harness) - something like that:
STEPCAFControl_Controller::Init();
STEPControl_Controller::Init();
Interface_Static::SetIVal ("write.step.nonmanifold", 1);
Interface_Static::SetIVal ("read.step.nonmanifold", 1);
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output.step (262,453 bytes) |
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I've attached the output.step file that I obtain after modifying the test-case to set the global "write.step.nonmanifold" option:
// g++ io.cpp -I/usr/local/occt/include/opencascade -L/usr/local/occt/lib -lTKSTEP -lTKSTEP209 -lTKSTEPAttr -lTKSTEPBase -lTKXSBase -lTKShHealing -lTKTopAlgo -lTKGeomAlgo -lTKBRep -lTKGeomBase -lTKG3d -lTKG2d -lTKMath -lTKernel -lfreetype
#include <BRepTools.hxx>
#include <BRep_Builder.hxx>
#include <Interface_Static.hxx>
#include <STEPControl_Controller.hxx>
#include <STEPControl_Writer.hxx>
int main()
{
TopoDS_Shape shape;
BRep_Builder builder;
BRepTools::Read(shape, "input.brep", builder);
BRepTools::Write(shape, "output.brep");
STEPControl_Controller::Init();
Interface_Static::SetIVal("write.step.nonmanifold", 1);
STEPControl_Writer writer;
writer.Transfer(shape, STEPControl_AsIs);
writer.Write("output.step");
return 0;
}
Unfortunately the new STEP output file now only contains 11 volumes (instead if 12). |
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> Unfortunately the new STEP output file now only contains 11 volumes (instead if 12). How you've counted them? Have you used > Interface_Static::SetIVal ("read.step.nonmanifold", 1); option to read STEP back? |
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Yes, I've tried both with and without setting "read.step.nonmanifold". Here's the updated test-case so you can directly give it a try on your side:
// g++ io.cpp -I/usr/local/occt/include/opencascade -L/usr/local/occt/lib -lTKSTEP -lTKSTEP209 -lTKSTEPAttr -lTKSTEPBase -lTKXSBase -lTKShHealing -lTKTopAlgo -lTKGeomAlgo -lTKBRep -lTKGeomBase -lTKG3d -lTKG2d -lTKMath -lTKernel -lfreetype
#include <iostream>
#include <BRepTools.hxx>
#include <BRep_Builder.hxx>
#include <Interface_Static.hxx>
#include <STEPControl_Controller.hxx>
#include <STEPControl_Writer.hxx>
#include <STEPControl_Reader.hxx>
#include <TopExp_Explorer.hxx>
int main()
{
TopoDS_Shape shape;
BRep_Builder builder;
BRepTools::Read(shape, "input.brep", builder);
TopExp_Explorer exp;
int in = 0;
for(exp.Init(shape, TopAbs_SOLID); exp.More(); exp.Next()) in++;
BRepTools::Write(shape, "output.brep");
STEPControl_Controller::Init();
Interface_Static::SetIVal("write.step.nonmanifold", 1);
STEPControl_Writer writer;
writer.Transfer(shape, STEPControl_AsIs);
writer.Write("output.step");
Interface_Static::SetIVal("read.step.nonmanifold", 1);
STEPControl_Reader reader;
reader.ReadFile("output.step");
reader.NbRootsForTransfer();
reader.TransferRoots();
TopoDS_Shape result = reader.OneShape();
int out = 0;
for(exp.Init(result, TopAbs_SOLID); exp.More(); exp.Next()) out++;
std::cout << in << " input solids, " << out << " output solids\n";
return 0;
}
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Here's a downstream bug report that I think stems from this issue: https://github.com/CadQuery/cadquery/issues/697 Is there anything we can do to work around the problem today? Incorrect step file generation feels like an important issue (to me personally). |
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grey.christoforo, > Here's a downstream bug report that I think stems from this issue I may be wrong, but I don't see how your issue is relevant to this one. Please register a dedicated bug - if it will be found that these bugs correlate to each other, this can be indicated later via bugs relations. |
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Any news about this? The issue is exactly the same as the one discussed here: This issue https://dev.opencascade.org/content/saving-compsolid-object |
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Dear OCCT team, I work at CERN and also would like to see this OCCT issue with the export to .step from .brep fixed. Is there any news on what could cause the issue and how much work it would be to fix it? Many thanks, Mariusz |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2021-02-15 21:55 | geuzaine | New Issue | |
| 2021-02-15 21:55 | geuzaine | Assigned To | => gka |
| 2021-02-15 21:55 | geuzaine | File Added: input.brep | |
| 2021-02-15 22:01 | kgv | Summary | STEP export duplicates surfaces, leading to non-conformal geometry => Data Exchange - STEP export duplicates surfaces, leading to non-conformal geometry |
| 2021-02-15 22:01 | kgv | Steps to Reproduce Updated | |
| 2021-02-15 22:08 | kgv | Relationship added | related to 0025092 |
| 2021-02-16 12:26 | kgv | Note Added: 0098888 | |
| 2021-02-16 14:47 | geuzaine | Note Added: 0098891 | |
| 2021-02-16 14:48 | geuzaine | Note Edited: 0098891 | |
| 2021-02-16 14:49 | kgv | File Added: i1.stp | |
| 2021-02-16 14:49 | kgv | File Added: i2.stp | |
| 2021-02-16 14:53 | kgv | Note Added: 0098892 | |
| 2021-02-16 15:53 | geuzaine | File Added: output.step | |
| 2021-02-16 15:55 | geuzaine | Note Added: 0098896 | |
| 2021-02-16 16:02 | kgv | Note Added: 0098897 | |
| 2021-02-16 16:14 | geuzaine | Note Added: 0098898 | |
| 2021-03-29 14:03 | grey.christoforo_170262 | Note Added: 0099813 | |
| 2021-03-29 14:18 | kgv | Note Added: 0099814 | |
| 2021-03-29 14:19 | kgv | Note Edited: 0099814 | |
| 2022-05-02 10:20 | geuzaine | Note Added: 0108282 | |
| 2023-01-20 13:42 | mawoznia | Note Added: 0112902 |
