Data Exchange - STEP export support of BRep shapes based on tessellated geometry

I upload the Recommended Practices for 3D Tessellated Geometry for STEP,
the document can be downloaded from here:
https://www.cax-if.org/documents/Attachment 1 (PDF)

Implementation of this functionality is not expected in the current version of the Open CASCADE. If you have an urgent need contact us via contact form:
https://www.opencascade.com/contact

Hello gka,

I do not have an urgent need for this functionality.

For the BRep shapes based on tessellated geometry, there are now serveral modeling alogirhtms support them, and can be displayed by the visualization module.

For data exchange module, it supports the BREP, STL tessellated shapes. Implementation other file format to exchange tessellated shapes data I think it is important functionality.

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Detailed log of new commits:

Author: Sergey NIKONOV
Date: Mon Apr 4 18:08:34 2022 +0300

    0030024: Data Exchange - STEP, IGES export support of BRep shapes based on tessellated geometry

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Sergey, Michail,

I've collected some formartting issues. See attached file.

Sergey, Michail,

I have some questions to the code. See attached file.

dox/user_guides/step/step.md
1159: only three columns are defined in this row, but table has 4 columns.

src/StepToTopoDS/StepToTopoDS_TranslateSolid.cxx
src/StepToTopoDS/StepToTopoDS_TranslateSolid.hxx
src/StepToTopoDS/StepToTopoDS_TranslateSolidError.hxx
Copy-paste errors in the file headers of new files: author, copyright, comment "gka 09.04.99".

src/StepVisual/StepVisual_TessellatedVertex.cxx
myPointIndex is not initialized in ctor.

src/TopoDSToStep/TopoDSToStep_MakeTessellatedItem.cxx
src/TopoDSToStep/TopoDSToStep_MakeTessellatedItem.hxx
Correct copyright year of new files.

src/TKSTEPBase/PACKAGES
Revert this change, as the added packages belong to another toolkit TKSTEPAttr.

tests/de_mesh/step_read/end
tests/de_mesh/step_write/end
Why such many images are generated? It is not a visualization test. I think it is enough only one.

Make the patch in occt-products to make working java and csharp samples. It is needed to wrap new classes in interface files in the folder occt-products\samples\swig.

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src/STEPControl/STEPControl_ActorWrite.cxx
Please correct indentation taking into account that tab size=8.

src/TKSTEPBase/PACKAGES

\ No newline at end of file

Please insert newline.

File: STEPControl_ActorWrite.cxx
Lines: 922-1177
Problem: need to replace tabs with spaces

Files: StepToTopoDS_TranslateSolid.hxx,
       StepToTopoDS_TranslateSolid.cxx,
       StepToTopoDS_TranslateSolidError.hxx,
       TopoDSToStep_MakeTessellatedItem.cxx,
       TopoDSToStep_MakeTessellatedItem.hxx
Problem: For newly created files must be one line about copyright, like in Graphic3d_Texture3D.cxx

Autogenerated files:
Problem: The year of the beginning of the copyright: 2021 -> 2022

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Detailed log of new commits:

Author: Sergey NIKONOV
Date: Mon Apr 4 18:08:34 2022 +0300

    0030024: Data Exchange - STEP, IGES export support of BRep shapes based on tessellated geometry
    
    Support of reading and writing tessellated geometry is added for the following STEP entities:
    - triangulated face
    - tessellated shell
    - tessellated solid
    - tessellated shape representation
    
    Models without BRep geometry (mesh formats like STL, OBJ and so on) are supported for writing to STEP.
    
    New parameters are added to enable/disable tessellated geometry reading and writing:
    - read.step.tessellated (On/Off)
    - write.step.tessellated (On/Off)
    Both of them are set to Off by default.
    
    Faces with poly triangulation are written in STEP as triangulated face entities with one coordinates list per face.
    Only one poly triangulation per face (returned by BRep_Tool::Triangulation) is written to STEP.

For integration:
occt - CR30024_1
products - CR30024

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For integration:
occt - CR30024
products - CR30024

Warning in csharp-sample and java-sample on Windows 64 with VC14, VC141, VC142

++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Project : CR0-WEEK-21_CR0-WEEK-21-Products-Windows-64-VC14-sample-csharp
++++++++++++++++++++++++++++++++++++++++++++++++++++++++

New warnings appears: 4
 
Type : MSBuild
Category : 322
File Name : E:/install/CR0-WEEK-21_CR0-WEEK-21/Windows-64-VC14-opt/Products/samples/csharp/../swig/TKSTEPAttr.i
Line : 53
Message : previous declaration of DownCast.

Type : MSBuild
Category : 322
File Name : E:/install/CR0-WEEK-21_CR0-WEEK-21/Windows-64-VC14-opt/Products/samples/csharp/../swig/TKSTEPAttr.i
Line : 53
Message : previous declaration of TypeOf.

In addition, please change the type of static flag read.step.tessellated from boolean to enum with 3 values:
On - tessellation is always read
Off - tessellation is always ignored
OnNoBRep - tessellation is read only for entities for which there is no BRep representation.

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tests/de_mesh/step_read/A1
6: this command is executed in 'end'.

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Detailed log of new commits:

Author: Sergey NIKONOV
Date: Mon May 30 19:11:56 2022 +0300

    0030024: Data Exchange - STEP, IGES export support of BRep shapes based on tessellated geometry
    
    #Reading of Complex_Triangulated_Face is added

tests/de_mesh/step_read/B1
This script does not perform XGetOneShape, so in the 'end' the source shape is checked instead of the final one.

tests/de_mesh/step_read/A2
tests/de_mesh/step_read/A3
Please add in the beginning 'puts' with corresponding bug title.

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I have no more remarks.
Commenter 5, please combine both branches in occt and products to obtain one commit.

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Sorry, one more remark. It is needed to add the option "OnNoBRep" for the parameter "write.step.tessellated".

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Detailed log of new commits:

Author: Sergey NIKONOV
Date: Thu Jun 2 12:12:22 2022 +0300

    #write.step.tessellated parameter OnNoBRep - tessellation is written only for entities for which there is no BRep representation

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In commit message:
- write.step.tessellated (On/Off) (Off by default)
Correct this info.

tests/de_mesh/step_write/end

# restore reading/writing tessellated STEP geometry default parameters
param read.step.tessellated Off
param write.step.tessellated Off

Default values are others.

tests/de_mesh/step_write/C2

# simple meshed box (mesh without brep)

The comment is incorrect, indeed brep with mesh.

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For integration:
occt - CR30024
products - CR30024

Combination -
OCCT branch : [archived branch]
master SHA - [revision removed]
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Products branch : [archived branch] SHA - [revision removed]
was compiled on Linux, MacOS and Windows platforms and tested in optimize mode.

Number of compiler warnings:
No new/fixed warnings

Regressions/Differences/Improvements:
No regressions/differences

CPU differences:
Debian80-64:
OCCT
Total CPU difference: 18736.560000000623 / 18755.550000000607 [-0.10%]
Products
Total CPU difference: 11708.410000000114 / 11723.710000000106 [-0.13%]
Windows-64-VC14:
OCCT
Total CPU difference: 20637.375 / 20721.125 [-0.40%]
Products
Total CPU difference: 13299.6875 / 13249.9375 [+0.38%]


Image differences :
No differences that require special attention

Memory differences :
No differences that require special attention

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I try this in opencascade-7.7.0-beta:
1 Load the data/occ/Top.brep and writeobj to save a obj file;
2 Load the obj file by ReadObj to a document;
3 Write the obj document to tessellated STEP file by WriteStep;
4 Load the tessellated STEP file by ReadStep;
5 Display the tessellated STEP file by XDisplay.